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  • Android应用程序启动过程源代码分析

    万次阅读 多人点赞 2011-08-19 00:58:02
    在Android系统中,应用程序是由Activity组成的,因此,应用程序的启动过程实际上就是应用程序中的默认Activity的启动过程,本文将详细分析应用程序框架层的源代码,了解Android应用程序的启动过程。 在上一篇文章...

            前文简要介绍了Android应用程序的Activity的启动过程。在Android系统中,应用程序是由Activity组成的,因此,应用程序的启动过程实际上就是应用程序中的默认Activity的启动过程,本文将详细分析应用程序框架层的源代码,了解Android应用程序的启动过程。

    《Android系统源代码情景分析》一书正在进击的程序员网(http://0xcc0xcd.com)中连载,点击进入!

            在上一篇文章Android应用程序的Activity启动过程简要介绍和学习计划中,我们举例子说明了启动Android应用程序中的Activity的两种情景,其中,在手机屏幕中点击应用程序图标的情景就会引发Android应用程序中的默认Activity的启动,从而把应用程序启动起来。这种启动方式的特点是会启动一个新的进程来加载相应的Activity。这里,我们继续以这个例子为例来说明Android应用程序的启动过程,即MainActivity的启动过程。

            MainActivity的启动过程如下图所示:


    点击查看大图

            下面详细分析每一步是如何实现的。

            Step 1. Launcher.startActivitySafely

            在Android系统中,应用程序是由Launcher启动起来的,其实,Launcher本身也是一个应用程序,其它的应用程序安装后,就会Launcher的界面上出现一个相应的图标,点击这个图标时,Launcher就会对应的应用程序启动起来。

            Launcher的源代码工程在packages/apps/Launcher2目录下,负责启动其它应用程序的源代码实现在src/com/android/launcher2/Launcher.java文件中:

    /**
    * Default launcher application.
    */
    public final class Launcher extends Activity
    		implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {
    
    	......
    
    	/**
    	* Launches the intent referred by the clicked shortcut.
    	*
    	* @param v The view representing the clicked shortcut.
    	*/
    	public void onClick(View v) {
    		Object tag = v.getTag();
    		if (tag instanceof ShortcutInfo) {
    			// Open shortcut
    			final Intent intent = ((ShortcutInfo) tag).intent;
    			int[] pos = new int[2];
    			v.getLocationOnScreen(pos);
    			intent.setSourceBounds(new Rect(pos[0], pos[1],
    				pos[0] + v.getWidth(), pos[1] + v.getHeight()));
    			startActivitySafely(intent, tag);
    		} else if (tag instanceof FolderInfo) {
    			......
    		} else if (v == mHandleView) {
    			......
    		}
    	}
    
    	void startActivitySafely(Intent intent, Object tag) {
    		intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    		try {
    			startActivity(intent);
    		} catch (ActivityNotFoundException e) {
    			......
    		} catch (SecurityException e) {
    			......
    		}
    	}
    
    	......
    
    }
            回忆一下前面一篇文章Android应用程序的Activity启动过程简要介绍和学习计划说到的应用程序Activity,它的默认Activity是MainActivity,这里是AndroidManifest.xml文件中配置的:

    <activity android:name=".MainActivity"  
          android:label="@string/app_name">  
           <intent-filter>  
            <action android:name="android.intent.action.MAIN" />  
            <category android:name="android.intent.category.LAUNCHER" />  
        </intent-filter>  
    </activity>  
            因此,这里的intent包含的信息为:action = "android.intent.action.Main",category="android.intent.category.LAUNCHER", cmp="shy.luo.activity/.MainActivity",表示它要启动的Activity为shy.luo.activity.MainActivity。Intent.FLAG_ACTIVITY_NEW_TASK表示要在一个新的Task中启动这个Activity,注意,Task是Android系统中的概念,它不同于进程Process的概念。简单地说,一个Task是一系列Activity的集合,这个集合是以堆栈的形式来组织的,遵循后进先出的原则。事实上,Task是一个非常复杂的概念,有兴趣的读者可以到官网http://developer.android.com/guide/topics/manifest/activity-element.html查看相关的资料。这里,我们只要知道,这个MainActivity要在一个新的Task中启动就可以了。

            Step 2. Activity.startActivity

            在Step 1中,我们看到,Launcher继承于Activity类,而Activity类实现了startActivity函数,因此,这里就调用了Activity.startActivity函数,它实现在frameworks/base/core/java/android/app/Activity.java文件中:

    public class Activity extends ContextThemeWrapper
    		implements LayoutInflater.Factory,
    		Window.Callback, KeyEvent.Callback,
    		OnCreateContextMenuListener, ComponentCallbacks {
    
    	......
    
    	@Override
    	public void startActivity(Intent intent) {
    		startActivityForResult(intent, -1);
    	}
    
    	......
    
    }
            这个函数实现很简单,它调用startActivityForResult来进一步处理,第二个参数传入-1表示不需要这个Actvity结束后的返回结果。

            Step 3. Activity.startActivityForResult

            这个函数也是实现在frameworks/base/core/java/android/app/Activity.java文件中:

    public class Activity extends ContextThemeWrapper
    		implements LayoutInflater.Factory,
    		Window.Callback, KeyEvent.Callback,
    		OnCreateContextMenuListener, ComponentCallbacks {
    
    	......
    
    	public void startActivityForResult(Intent intent, int requestCode) {
    		if (mParent == null) {
    			Instrumentation.ActivityResult ar =
    				mInstrumentation.execStartActivity(
    				this, mMainThread.getApplicationThread(), mToken, this,
    				intent, requestCode);
    			......
    		} else {
    			......
    		}
    
    
    	......
    
    }
             这里的mInstrumentation是Activity类的成员变量,它的类型是Intrumentation,定义在frameworks/base/core/java/android/app/Instrumentation.java文件中,它用来监控应用程序和系统的交互。

             这里的mMainThread也是Activity类的成员变量,它的类型是ActivityThread,它代表的是应用程序的主线程,我们在Android系统在新进程中启动自定义服务过程(startService)的原理分析一文中已经介绍过了。这里通过mMainThread.getApplicationThread获得它里面的ApplicationThread成员变量,它是一个Binder对象,后面我们会看到,ActivityManagerService会使用它来和ActivityThread来进行进程间通信。这里我们需注意的是,这里的mMainThread代表的是Launcher应用程序运行的进程。

             这里的mToken也是Activity类的成员变量,它是一个Binder对象的远程接口。

             Step 4. Instrumentation.execStartActivity
             这个函数定义在frameworks/base/core/java/android/app/Instrumentation.java文件中:

    public class Instrumentation {
    
    	......
    
    	public ActivityResult execStartActivity(
    	Context who, IBinder contextThread, IBinder token, Activity target,
    	Intent intent, int requestCode) {
    		IApplicationThread whoThread = (IApplicationThread) contextThread;
    		if (mActivityMonitors != null) {
    			......
    		}
    		try {
    			int result = ActivityManagerNative.getDefault()
    				.startActivity(whoThread, intent,
    				intent.resolveTypeIfNeeded(who.getContentResolver()),
    				null, 0, token, target != null ? target.mEmbeddedID : null,
    				requestCode, false, false);
    			......
    		} catch (RemoteException e) {
    		}
    		return null;
    	}
    
    	......
    
    }
             这里的ActivityManagerNative.getDefault返回ActivityManagerService的远程接口,即ActivityManagerProxy接口,具体可以参考Android系统在新进程中启动自定义服务过程(startService)的原理分析一文。

             这里的intent.resolveTypeIfNeeded返回这个intent的MIME类型,在这个例子中,没有AndroidManifest.xml设置MainActivity的MIME类型,因此,这里返回null。

             这里的target不为null,但是target.mEmbddedID为null,我们不用关注。

             Step 5. ActivityManagerProxy.startActivity

             这个函数定义在frameworks/base/core/java/android/app/ActivityManagerNative.java文件中:

    class ActivityManagerProxy implements IActivityManager
    {
    
    	......
    
    	public int startActivity(IApplicationThread caller, Intent intent,
    			String resolvedType, Uri[] grantedUriPermissions, int grantedMode,
    			IBinder resultTo, String resultWho,
    			int requestCode, boolean onlyIfNeeded,
    			boolean debug) throws RemoteException {
    		Parcel data = Parcel.obtain();
    		Parcel reply = Parcel.obtain();
    		data.writeInterfaceToken(IActivityManager.descriptor);
    		data.writeStrongBinder(caller != null ? caller.asBinder() : null);
    		intent.writeToParcel(data, 0);
    		data.writeString(resolvedType);
    		data.writeTypedArray(grantedUriPermissions, 0);
    		data.writeInt(grantedMode);
    		data.writeStrongBinder(resultTo);
    		data.writeString(resultWho);
    		data.writeInt(requestCode);
    		data.writeInt(onlyIfNeeded ? 1 : 0);
    		data.writeInt(debug ? 1 : 0);
    		mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0);
    		reply.readException();
    		int result = reply.readInt();
    		reply.recycle();
    		data.recycle();
    		return result;
    	}
    
    	......
    
    }
            这里的参数比较多,我们先整理一下。从上面的调用可以知道,这里的参数resolvedType、grantedUriPermissions和resultWho均为null;参数caller为ApplicationThread类型的Binder实体;参数resultTo为一个Binder实体的远程接口,我们先不关注它;参数grantedMode为0,我们也先不关注它;参数requestCode为-1;参数onlyIfNeeded和debug均空false。

            Step 6. ActivityManagerService.startActivity

            上一步Step 5通过Binder驱动程序就进入到ActivityManagerService的startActivity函数来了,它定义在frameworks/base/services/java/com/android/server/am/ActivityManagerService.java文件中:

    public final class ActivityManagerService extends ActivityManagerNative
    		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    
    	......
    
    	public final int startActivity(IApplicationThread caller,
    			Intent intent, String resolvedType, Uri[] grantedUriPermissions,
    			int grantedMode, IBinder resultTo,
    			String resultWho, int requestCode, boolean onlyIfNeeded,
    			boolean debug) {
    		return mMainStack.startActivityMayWait(caller, intent, resolvedType,
    			grantedUriPermissions, grantedMode, resultTo, resultWho,
    			requestCode, onlyIfNeeded, debug, null, null);
    	}
    
    
    	......
    
    }
            这里只是简单地将操作转发给成员变量mMainStack的startActivityMayWait函数,这里的mMainStack的类型为ActivityStack。

            Step 7. ActivityStack.startActivityMayWait

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	final int startActivityMayWait(IApplicationThread caller,
    			Intent intent, String resolvedType, Uri[] grantedUriPermissions,
    			int grantedMode, IBinder resultTo,
    			String resultWho, int requestCode, boolean onlyIfNeeded,
    			boolean debug, WaitResult outResult, Configuration config) {
    
    		......
    
    		boolean componentSpecified = intent.getComponent() != null;
    
    		// Don't modify the client's object!
    		intent = new Intent(intent);
    
    		// Collect information about the target of the Intent.
    		ActivityInfo aInfo;
    		try {
    			ResolveInfo rInfo =
    				AppGlobals.getPackageManager().resolveIntent(
    				intent, resolvedType,
    				PackageManager.MATCH_DEFAULT_ONLY
    				| ActivityManagerService.STOCK_PM_FLAGS);
    			aInfo = rInfo != null ? rInfo.activityInfo : null;
    		} catch (RemoteException e) {
    			......
    		}
    
    		if (aInfo != null) {
    			// Store the found target back into the intent, because now that
    			// we have it we never want to do this again.  For example, if the
    			// user navigates back to this point in the history, we should
    			// always restart the exact same activity.
    			intent.setComponent(new ComponentName(
    				aInfo.applicationInfo.packageName, aInfo.name));
    			......
    		}
    
    		synchronized (mService) {
    			int callingPid;
    			int callingUid;
    			if (caller == null) {
    				......
    			} else {
    				callingPid = callingUid = -1;
    			}
    
    			mConfigWillChange = config != null
    				&& mService.mConfiguration.diff(config) != 0;
    
    			......
    
    			if (mMainStack && aInfo != null &&
    				(aInfo.applicationInfo.flags&ApplicationInfo.FLAG_CANT_SAVE_STATE) != 0) {
    				  
    		              ......
    
    			}
    
    			int res = startActivityLocked(caller, intent, resolvedType,
    				grantedUriPermissions, grantedMode, aInfo,
    				resultTo, resultWho, requestCode, callingPid, callingUid,
    				onlyIfNeeded, componentSpecified);
    
    			if (mConfigWillChange && mMainStack) {
    				......
    			}
    
    			......
    
    			if (outResult != null) {
    				......
    			}
    
    			return res;
    		}
    
    	}
    
    	......
    
    }
            注意,从Step 6传下来的参数outResult和config均为null,此外,表达式(aInfo.applicationInfo.flags&ApplicationInfo.FLAG_CANT_SAVE_STATE) != 0为false,因此,这里忽略了无关代码。

            下面语句对参数intent的内容进行解析,得到MainActivity的相关信息,保存在aInfo变量中:

        ActivityInfo aInfo;
        try {
    	ResolveInfo rInfo =
    	AppGlobals.getPackageManager().resolveIntent(
    		intent, resolvedType,
    		PackageManager.MATCH_DEFAULT_ONLY
    		| ActivityManagerService.STOCK_PM_FLAGS);
    	aInfo = rInfo != null ? rInfo.activityInfo : null;
        } catch (RemoteException e) {
    		......
        }
            解析之后,得到的aInfo.applicationInfo.packageName的值为"shy.luo.activity",aInfo.name的值为"shy.luo.activity.MainActivity",这是在这个实例的配置文件AndroidManifest.xml里面配置的。

            此外,函数开始的地方调用intent.getComponent()函数的返回值不为null,因此,这里的componentSpecified变量为true。

            接下去就调用startActivityLocked进一步处理了。

            Step 8. ActivityStack.startActivityLocked

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	final int startActivityLocked(IApplicationThread caller,
    		    Intent intent, String resolvedType,
    		    Uri[] grantedUriPermissions,
    		    int grantedMode, ActivityInfo aInfo, IBinder resultTo,
    	            String resultWho, int requestCode,
    		    int callingPid, int callingUid, boolean onlyIfNeeded,
    		    boolean componentSpecified) {
    	        int err = START_SUCCESS;
    
    		ProcessRecord callerApp = null;
    		if (caller != null) {
    			callerApp = mService.getRecordForAppLocked(caller);
    			if (callerApp != null) {
    				callingPid = callerApp.pid;
    				callingUid = callerApp.info.uid;
    			} else {
    				......
    			}
    		}
    
    		......
    
    		ActivityRecord sourceRecord = null;
    		ActivityRecord resultRecord = null;
    		if (resultTo != null) {
    			int index = indexOfTokenLocked(resultTo);
    			
    			......
    				
    			if (index >= 0) {
    				sourceRecord = (ActivityRecord)mHistory.get(index);
    				if (requestCode >= 0 && !sourceRecord.finishing) {
    					......
    				}
    			}
    		}
    
    		int launchFlags = intent.getFlags();
    
    		if ((launchFlags&Intent.FLAG_ACTIVITY_FORWARD_RESULT) != 0
    			&& sourceRecord != null) {
    			......
    		}
    
    		if (err == START_SUCCESS && intent.getComponent() == null) {
    			......
    		}
    
    		if (err == START_SUCCESS && aInfo == null) {
    			......
    		}
    
    		if (err != START_SUCCESS) {
    			......
    		}
    
    		......
    
    		ActivityRecord r = new ActivityRecord(mService, this, callerApp, callingUid,
    			intent, resolvedType, aInfo, mService.mConfiguration,
    			resultRecord, resultWho, requestCode, componentSpecified);
    
    		......
    
    		return startActivityUncheckedLocked(r, sourceRecord,
    			grantedUriPermissions, grantedMode, onlyIfNeeded, true);
    	}
    
    
    	......
    
    }
            从传进来的参数caller得到调用者的进程信息,并保存在callerApp变量中,这里就是Launcher应用程序的进程信息了。

            前面说过,参数resultTo是Launcher这个Activity里面的一个Binder对象,通过它可以获得Launcher这个Activity的相关信息,保存在sourceRecord变量中。
            再接下来,创建即将要启动的Activity的相关信息,并保存在r变量中:

    ActivityRecord r = new ActivityRecord(mService, this, callerApp, callingUid,
    	intent, resolvedType, aInfo, mService.mConfiguration,
    	resultRecord, resultWho, requestCode, componentSpecified);
            接着调用startActivityUncheckedLocked函数进行下一步操作。

            Step 9. ActivityStack.startActivityUncheckedLocked

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	final int startActivityUncheckedLocked(ActivityRecord r,
    		ActivityRecord sourceRecord, Uri[] grantedUriPermissions,
    		int grantedMode, boolean onlyIfNeeded, boolean doResume) {
    		final Intent intent = r.intent;
    		final int callingUid = r.launchedFromUid;
    
    		int launchFlags = intent.getFlags();
    
    		// We'll invoke onUserLeaving before onPause only if the launching
    		// activity did not explicitly state that this is an automated launch.
    		mUserLeaving = (launchFlags&Intent.FLAG_ACTIVITY_NO_USER_ACTION) == 0;
    		
    		......
    
    		ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
    			!= 0 ? r : null;
    
    		// If the onlyIfNeeded flag is set, then we can do this if the activity
    		// being launched is the same as the one making the call...  or, as
    		// a special case, if we do not know the caller then we count the
    		// current top activity as the caller.
    		if (onlyIfNeeded) {
    			......
    		}
    
    		if (sourceRecord == null) {
    			......
    		} else if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
    			......
    		} else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
    			|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
    			......
    		}
    
    		if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
    			......
    		}
    
    		boolean addingToTask = false;
    		if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
    			(launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
    			|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
    			|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
    				// If bring to front is requested, and no result is requested, and
    				// we can find a task that was started with this same
    				// component, then instead of launching bring that one to the front.
    				if (r.resultTo == null) {
    					// See if there is a task to bring to the front.  If this is
    					// a SINGLE_INSTANCE activity, there can be one and only one
    					// instance of it in the history, and it is always in its own
    					// unique task, so we do a special search.
    					ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
    						? findTaskLocked(intent, r.info)
    						: findActivityLocked(intent, r.info);
    					if (taskTop != null) {
    						......
    					}
    				}
    		}
    
    		......
    
    		if (r.packageName != null) {
    			// If the activity being launched is the same as the one currently
    			// at the top, then we need to check if it should only be launched
    			// once.
    			ActivityRecord top = topRunningNonDelayedActivityLocked(notTop);
    			if (top != null && r.resultTo == null) {
    				if (top.realActivity.equals(r.realActivity)) {
    					......
    				}
    			}
    
    		} else {
    			......
    		}
    
    		boolean newTask = false;
    
    		// Should this be considered a new task?
    		if (r.resultTo == null && !addingToTask
    			&& (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
    				// todo: should do better management of integers.
    				mService.mCurTask++;
    				if (mService.mCurTask <= 0) {
    					mService.mCurTask = 1;
    				}
    				r.task = new TaskRecord(mService.mCurTask, r.info, intent,
    					(r.info.flags&ActivityInfo.FLAG_CLEAR_TASK_ON_LAUNCH) != 0);
    				......
    				newTask = true;
    				if (mMainStack) {
    					mService.addRecentTaskLocked(r.task);
    				}
    
    		} else if (sourceRecord != null) {
    			......
    		} else {
    			......
    		}
    
    		......
    
    		startActivityLocked(r, newTask, doResume);
    		return START_SUCCESS;
    	}
    
    	......
    
    }
            函数首先获得intent的标志值,保存在launchFlags变量中。

            这个intent的标志值的位Intent.FLAG_ACTIVITY_NO_USER_ACTION没有置位,因此 ,成员变量mUserLeaving的值为true。

            这个intent的标志值的位Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP也没有置位,因此,变量notTop的值为null。

            由于在这个例子的AndroidManifest.xml文件中,MainActivity没有配置launchMode属值,因此,这里的r.launchMode为默认值0,表示以标准(Standard,或者称为ActivityInfo.LAUNCH_MULTIPLE)的方式来启动这个Activity。Activity的启动方式有四种,其余三种分别是ActivityInfo.LAUNCH_SINGLE_INSTANCE、ActivityInfo.LAUNCH_SINGLE_TASK和ActivityInfo.LAUNCH_SINGLE_TOP,具体可以参考官方网站http://developer.android.com/reference/android/content/pm/ActivityInfo.html

            传进来的参数r.resultTo为null,表示Launcher不需要等这个即将要启动的MainActivity的执行结果。

            由于这个intent的标志值的位Intent.FLAG_ACTIVITY_NEW_TASK被置位,而且Intent.FLAG_ACTIVITY_MULTIPLE_TASK没有置位,因此,下面的if语句会被执行:

        if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
    	(launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
    	|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
    	|| r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
    		// If bring to front is requested, and no result is requested, and
    		// we can find a task that was started with this same
    		// component, then instead of launching bring that one to the front.
    		if (r.resultTo == null) {
    			// See if there is a task to bring to the front.  If this is
    			// a SINGLE_INSTANCE activity, there can be one and only one
    			// instance of it in the history, and it is always in its own
    			// unique task, so we do a special search.
    			ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
    				? findTaskLocked(intent, r.info)
    				: findActivityLocked(intent, r.info);
    			if (taskTop != null) {
    				......
    			}
    		}
        }
            这段代码的逻辑是查看一下,当前有没有Task可以用来执行这个Activity。由于r.launchMode的值不为ActivityInfo.LAUNCH_SINGLE_INSTANCE,因此,它通过findTaskLocked函数来查找存不存这样的Task,这里返回的结果是null,即taskTop为null,因此,需要创建一个新的Task来启动这个Activity。

            接着往下看:

        if (r.packageName != null) {
    	// If the activity being launched is the same as the one currently
    	// at the top, then we need to check if it should only be launched
    	// once.
    	ActivityRecord top = topRunningNonDelayedActivityLocked(notTop);
    	if (top != null && r.resultTo == null) {
    		if (top.realActivity.equals(r.realActivity)) {
    			......
    		}
    	}
    
        } 
            这段代码的逻辑是看一下,当前在堆栈顶端的Activity是否就是即将要启动的Activity,有些情况下,如果即将要启动的Activity就在堆栈的顶端,那么,就不会重新启动这个Activity的别一个实例了,具体可以参考官方网站http://developer.android.com/reference/android/content/pm/ActivityInfo.html。现在处理堆栈顶端的Activity是Launcher,与我们即将要启动的MainActivity不是同一个Activity,因此,这里不用进一步处理上述介绍的情况。

           执行到这里,我们知道,要在一个新的Task里面来启动这个Activity了,于是新创建一个Task:

       if (r.resultTo == null && !addingToTask
    	&& (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
    	// todo: should do better management of integers.
    	mService.mCurTask++;
    	if (mService.mCurTask <= 0) {
    		mService.mCurTask = 1;
    	}
    	r.task = new TaskRecord(mService.mCurTask, r.info, intent,
    		(r.info.flags&ActivityInfo.FLAG_CLEAR_TASK_ON_LAUNCH) != 0);
    	......
    	newTask = true;
    	if (mMainStack) {
    		mService.addRecentTaskLocked(r.task);
    	}
    
        }
            新建的Task保存在r.task域中,同时,添加到mService中去,这里的mService就是ActivityManagerService了。

            最后就进入startActivityLocked(r, newTask, doResume)进一步处理了。这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	private final void startActivityLocked(ActivityRecord r, boolean newTask,
    			boolean doResume) {
    		final int NH = mHistory.size();
    
    		int addPos = -1;
    
    		if (!newTask) {
    			......
    		}
    
    		// Place a new activity at top of stack, so it is next to interact
    		// with the user.
    		if (addPos < 0) {
    			addPos = NH;
    		}
    
    		// If we are not placing the new activity frontmost, we do not want
    		// to deliver the onUserLeaving callback to the actual frontmost
    		// activity
    		if (addPos < NH) {
    			......
    		}
    
    		// Slot the activity into the history stack and proceed
    		mHistory.add(addPos, r);
    		r.inHistory = true;
    		r.frontOfTask = newTask;
    		r.task.numActivities++;
    		if (NH > 0) {
    			// We want to show the starting preview window if we are
    			// switching to a new task, or the next activity's process is
    			// not currently running.
    			......
    		} else {
    			// If this is the first activity, don't do any fancy animations,
    			// because there is nothing for it to animate on top of.
    			......
    		}
    		
    		......
    
    		if (doResume) {
    			resumeTopActivityLocked(null);
    		}
    	}
    
    	......
    
    }
            这里的NH表示当前系统中历史任务的个数,这里肯定是大于0,因为Launcher已经跑起来了。当NH>0时,并且现在要切换新任务时,要做一些任务切的界面操作,这段代码我们就不看了,这里不会影响到下面启Activity的过程,有兴趣的读取可以自己研究一下。

            这里传进来的参数doResume为true,于是调用resumeTopActivityLocked进一步操作。

            Step 10. Activity.resumeTopActivityLocked

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	/**
    	* Ensure that the top activity in the stack is resumed.
    	*
    	* @param prev The previously resumed activity, for when in the process
    	* of pausing; can be null to call from elsewhere.
    	*
    	* @return Returns true if something is being resumed, or false if
    	* nothing happened.
    	*/
    	final boolean resumeTopActivityLocked(ActivityRecord prev) {
    		// Find the first activity that is not finishing.
    		ActivityRecord next = topRunningActivityLocked(null);
    
    		// Remember how we'll process this pause/resume situation, and ensure
    		// that the state is reset however we wind up proceeding.
    		final boolean userLeaving = mUserLeaving;
    		mUserLeaving = false;
    
    		if (next == null) {
    			......
    		}
    
    		next.delayedResume = false;
    
    		// If the top activity is the resumed one, nothing to do.
    		if (mResumedActivity == next && next.state == ActivityState.RESUMED) {
    			......
    		}
    
    		// If we are sleeping, and there is no resumed activity, and the top
    		// activity is paused, well that is the state we want.
    		if ((mService.mSleeping || mService.mShuttingDown)
    			&& mLastPausedActivity == next && next.state == ActivityState.PAUSED) {
    			......
    		}
    
    		......
    
    		// If we are currently pausing an activity, then don't do anything
    		// until that is done.
    		if (mPausingActivity != null) {
    			......
    		}
    
    		......
    
    		// We need to start pausing the current activity so the top one
    		// can be resumed...
    		if (mResumedActivity != null) {
    			......
    			startPausingLocked(userLeaving, false);
    			return true;
    		}
    
    		......
    	}
    
    	......
    
    }
            函数先通过调用topRunningActivityLocked函数获得堆栈顶端的Activity,这里就是MainActivity了,这是在上面的Step 9设置好的,保存在next变量中。 

           接下来把mUserLeaving的保存在本地变量userLeaving中,然后重新设置为false,在上面的Step 9中,mUserLeaving的值为true,因此,这里的userLeaving为true。

           这里的mResumedActivity为Launcher,因为Launcher是当前正被执行的Activity。

           当我们处理休眠状态时,mLastPausedActivity保存堆栈顶端的Activity,因为当前不是休眠状态,所以mLastPausedActivity为null。

           有了这些信息之后,下面的语句就容易理解了:

        // If the top activity is the resumed one, nothing to do.
        if (mResumedActivity == next && next.state == ActivityState.RESUMED) {
    	......
        }
    
        // If we are sleeping, and there is no resumed activity, and the top
        // activity is paused, well that is the state we want.
        if ((mService.mSleeping || mService.mShuttingDown)
    	&& mLastPausedActivity == next && next.state == ActivityState.PAUSED) {
    	......
        }
            它首先看要启动的Activity是否就是当前处理Resumed状态的Activity,如果是的话,那就什么都不用做,直接返回就可以了;否则再看一下系统当前是否休眠状态,如果是的话,再看看要启动的Activity是否就是当前处于堆栈顶端的Activity,如果是的话,也是什么都不用做。

            上面两个条件都不满足,因此,在继续往下执行之前,首先要把当处于Resumed状态的Activity推入Paused状态,然后才可以启动新的Activity。但是在将当前这个Resumed状态的Activity推入Paused状态之前,首先要看一下当前是否有Activity正在进入Pausing状态,如果有的话,当前这个Resumed状态的Activity就要稍后才能进入Paused状态了,这样就保证了所有需要进入Paused状态的Activity串行处理。

            这里没有处于Pausing状态的Activity,即mPausingActivity为null,而且mResumedActivity也不为null,于是就调用startPausingLocked函数把Launcher推入Paused状态去了。

            Step 11. ActivityStack.startPausingLocked

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	private final void startPausingLocked(boolean userLeaving, boolean uiSleeping) {
    		if (mPausingActivity != null) {
    			......
    		}
    		ActivityRecord prev = mResumedActivity;
    		if (prev == null) {
    			......
    		}
    		......
    		mResumedActivity = null;
    		mPausingActivity = prev;
    		mLastPausedActivity = prev;
    		prev.state = ActivityState.PAUSING;
    		......
    
    		if (prev.app != null && prev.app.thread != null) {
    			......
    			try {
    				......
    				prev.app.thread.schedulePauseActivity(prev, prev.finishing, userLeaving,
    					prev.configChangeFlags);
    				......
    			} catch (Exception e) {
    				......
    			}
    		} else {
    			......
    		}
    
    		......
    	
    	}
    
    	......
    
    }

            函数首先把mResumedActivity保存在本地变量prev中。在上一步Step 10中,说到mResumedActivity就是Launcher,因此,这里把Launcher进程中的ApplicationThread对象取出来,通过它来通知Launcher这个Activity它要进入Paused状态了。当然,这里的prev.app.thread是一个ApplicationThread对象的远程接口,通过调用这个远程接口的schedulePauseActivity来通知Launcher进入Paused状态。

           参数prev.finishing表示prev所代表的Activity是否正在等待结束的Activity列表中,由于Laucher这个Activity还没结束,所以这里为false;参数prev.configChangeFlags表示哪些config发生了变化,这里我们不关心它的值。

           Step 12. ApplicationThreadProxy.schedulePauseActivity

           这个函数定义在frameworks/base/core/java/android/app/ApplicationThreadNative.java文件中:

    class ApplicationThreadProxy implements IApplicationThread {
    	
    	......
    
    	public final void schedulePauseActivity(IBinder token, boolean finished,
    	boolean userLeaving, int configChanges) throws RemoteException {
    		Parcel data = Parcel.obtain();
    		data.writeInterfaceToken(IApplicationThread.descriptor);
    		data.writeStrongBinder(token);
    		data.writeInt(finished ? 1 : 0);
    		data.writeInt(userLeaving ? 1 :0);
    		data.writeInt(configChanges);
    		mRemote.transact(SCHEDULE_PAUSE_ACTIVITY_TRANSACTION, data, null,
    			IBinder.FLAG_ONEWAY);
    		data.recycle();
    	}
    
    	......
    
    }

            这个函数通过Binder进程间通信机制进入到ApplicationThread.schedulePauseActivity函数中。

            Step 13. ApplicationThread.schedulePauseActivity

            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中,它是ActivityThread的内部类:

    public final class ActivityThread {
    	
    	......
    
    	private final class ApplicationThread extends ApplicationThreadNative {
    		
    		......
    
    		public final void schedulePauseActivity(IBinder token, boolean finished,
    				boolean userLeaving, int configChanges) {
    			queueOrSendMessage(
    				finished ? H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY,
    				token,
    				(userLeaving ? 1 : 0),
    				configChanges);
    		}
    
    		......
    
    	}
    
    	......
    
    }
            这里调用的函数queueOrSendMessage是ActivityThread类的成员函数。

           上面说到,这里的finished值为false,因此,queueOrSendMessage的第一个参数值为H.PAUSE_ACTIVITY,表示要暂停token所代表的Activity,即Launcher。

           Step 14. ActivityThread.queueOrSendMessage

           这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    	
    	......
    
    	private final void queueOrSendMessage(int what, Object obj, int arg1) {
    		queueOrSendMessage(what, obj, arg1, 0);
    	}
    
    	private final void queueOrSendMessage(int what, Object obj, int arg1, int arg2) {
    		synchronized (this) {
    			......
    			Message msg = Message.obtain();
    			msg.what = what;
    			msg.obj = obj;
    			msg.arg1 = arg1;
    			msg.arg2 = arg2;
    			mH.sendMessage(msg);
    		}
    	}
    
    	......
    
    }
            这里首先将相关信息组装成一个msg,然后通过mH成员变量发送出去,mH的类型是H,继承于Handler类,是ActivityThread的内部类,因此,这个消息最后由H.handleMessage来处理。

            Step 15. H.handleMessage

            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    	
    	......
    
    	private final class H extends Handler {
    
    		......
    
    		public void handleMessage(Message msg) {
    			......
    			switch (msg.what) {
    			
    			......
    			
    			case PAUSE_ACTIVITY:
    				handlePauseActivity((IBinder)msg.obj, false, msg.arg1 != 0, msg.arg2);
    				maybeSnapshot();
    				break;
    
    			......
    
    			}
    		......
    
    	}
    
    	......
    
    }

            这里调用ActivityThread.handlePauseActivity进一步操作,msg.obj是一个ActivityRecord对象的引用,它代表的是Launcher这个Activity。
            Step 16. ActivityThread.handlePauseActivity

            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    	
    	......
    
    	private final void handlePauseActivity(IBinder token, boolean finished,
    			boolean userLeaving, int configChanges) {
    
    		ActivityClientRecord r = mActivities.get(token);
    		if (r != null) {
    			//Slog.v(TAG, "userLeaving=" + userLeaving + " handling pause of " + r);
    			if (userLeaving) {
    				performUserLeavingActivity(r);
    			}
    
    			r.activity.mConfigChangeFlags |= configChanges;
    			Bundle state = performPauseActivity(token, finished, true);
    
    			// Make sure any pending writes are now committed.
    			QueuedWork.waitToFinish();
    
    			// Tell the activity manager we have paused.
    			try {
    				ActivityManagerNative.getDefault().activityPaused(token, state);
    			} catch (RemoteException ex) {
    			}
    		}
    	}
    
    	......
    
    }
             函数首先将Binder引用token转换成ActivityRecord的远程接口ActivityClientRecord,然后做了三个事情:1. 如果userLeaving为true,则通过调用performUserLeavingActivity函数来调用Activity.onUserLeaveHint通知Activity,用户要离开它了;2. 调用performPauseActivity函数来调用Activity.onPause函数,我们知道,在Activity的生命周期中,当它要让位于其它的Activity时,系统就会调用它的onPause函数;3. 它通知ActivityManagerService,这个Activity已经进入Paused状态了,ActivityManagerService现在可以完成未竟的事情,即启动MainActivity了。

            Step 17. ActivityManagerProxy.activityPaused

            这个函数定义在frameworks/base/core/java/android/app/ActivityManagerNative.java文件中:

    class ActivityManagerProxy implements IActivityManager
    {
    	......
    
    	public void activityPaused(IBinder token, Bundle state) throws RemoteException
    	{
    		Parcel data = Parcel.obtain();
    		Parcel reply = Parcel.obtain();
    		data.writeInterfaceToken(IActivityManager.descriptor);
    		data.writeStrongBinder(token);
    		data.writeBundle(state);
    		mRemote.transact(ACTIVITY_PAUSED_TRANSACTION, data, reply, 0);
    		reply.readException();
    		data.recycle();
    		reply.recycle();
    	}
    
    	......
    
    }
            这里通过Binder进程间通信机制就进入到ActivityManagerService.activityPaused函数中去了。

            Step 18. ActivityManagerService.activityPaused

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityManagerService.java文件中:

    public final class ActivityManagerService extends ActivityManagerNative
    			implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    	......
    
    	public final void activityPaused(IBinder token, Bundle icicle) {
    		
    		......
    
    		final long origId = Binder.clearCallingIdentity();
    		mMainStack.activityPaused(token, icicle, false);
    		
    		......
    	}
    
    	......
    
    }
           这里,又再次进入到ActivityStack类中,执行activityPaused函数。

           Step 19. ActivityStack.activityPaused

           这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	final void activityPaused(IBinder token, Bundle icicle, boolean timeout) {
    		
    		......
    
    		ActivityRecord r = null;
    
    		synchronized (mService) {
    			int index = indexOfTokenLocked(token);
    			if (index >= 0) {
    				r = (ActivityRecord)mHistory.get(index);
    				if (!timeout) {
    					r.icicle = icicle;
    					r.haveState = true;
    				}
    				mHandler.removeMessages(PAUSE_TIMEOUT_MSG, r);
    				if (mPausingActivity == r) {
    					r.state = ActivityState.PAUSED;
    					completePauseLocked();
    				} else {
    					......
    				}
    			}
    		}
    	}
    
    	......
    
    }
           这里通过参数token在mHistory列表中得到ActivityRecord,从上面我们知道,这个ActivityRecord代表的是Launcher这个Activity,而我们在Step 11中,把Launcher这个Activity的信息保存在mPausingActivity中,因此,这里mPausingActivity等于r,于是,执行completePauseLocked操作。

           Step 20. ActivityStack.completePauseLocked

           这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	private final void completePauseLocked() {
    		ActivityRecord prev = mPausingActivity;
    		
    		......
    
    		if (prev != null) {
    
    			......
    
    			mPausingActivity = null;
    		}
    
    		if (!mService.mSleeping && !mService.mShuttingDown) {
    			resumeTopActivityLocked(prev);
    		} else {
    			......
    		}
    
    		......
    	}
    
    	......
    
    }
            函数首先把mPausingActivity变量清空,因为现在不需要它了,然后调用resumeTopActivityLokced进一步操作,它传入的参数即为代表Launcher这个Activity的ActivityRecord。

            Step 21. ActivityStack.resumeTopActivityLokced
            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	final boolean resumeTopActivityLocked(ActivityRecord prev) {
    		......
    
    		// Find the first activity that is not finishing.
    		ActivityRecord next = topRunningActivityLocked(null);
    
    		// Remember how we'll process this pause/resume situation, and ensure
    		// that the state is reset however we wind up proceeding.
    		final boolean userLeaving = mUserLeaving;
    		mUserLeaving = false;
    
    		......
    
    		next.delayedResume = false;
    
    		// If the top activity is the resumed one, nothing to do.
    		if (mResumedActivity == next && next.state == ActivityState.RESUMED) {
    			......
    			return false;
    		}
    
    		// If we are sleeping, and there is no resumed activity, and the top
    		// activity is paused, well that is the state we want.
    		if ((mService.mSleeping || mService.mShuttingDown)
    			&& mLastPausedActivity == next && next.state == ActivityState.PAUSED) {
    			......
    			return false;
    		}
    
    		.......
    
    
    		// We need to start pausing the current activity so the top one
    		// can be resumed...
    		if (mResumedActivity != null) {
    			......
    			return true;
    		}
    
    		......
    
    
    		if (next.app != null && next.app.thread != null) {
    			......
    
    		} else {
    			......
    			startSpecificActivityLocked(next, true, true);
    		}
    
    		return true;
    	}
    
    
    	......
    
    }
            通过上面的Step 9,我们知道,当前在堆栈顶端的Activity为我们即将要启动的MainActivity,这里通过调用topRunningActivityLocked将它取回来,保存在next变量中。之前最后一个Resumed状态的Activity,即Launcher,到了这里已经处于Paused状态了,因此,mResumedActivity为null。最后一个处于Paused状态的Activity为Launcher,因此,这里的mLastPausedActivity就为Launcher。前面我们为MainActivity创建了ActivityRecord后,它的app域一直保持为null。有了这些信息后,上面这段代码就容易理解了,它最终调用startSpecificActivityLocked进行下一步操作。

           Step 22. ActivityStack.startSpecificActivityLocked
           这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	private final void startSpecificActivityLocked(ActivityRecord r,
    			boolean andResume, boolean checkConfig) {
    		// Is this activity's application already running?
    		ProcessRecord app = mService.getProcessRecordLocked(r.processName,
    			r.info.applicationInfo.uid);
    
    		......
    
    		if (app != null && app.thread != null) {
    			try {
    				realStartActivityLocked(r, app, andResume, checkConfig);
    				return;
    			} catch (RemoteException e) {
    				......
    			}
    		}
    
    		mService.startProcessLocked(r.processName, r.info.applicationInfo, true, 0,
    			"activity", r.intent.getComponent(), false);
    	}
    
    
    	......
    
    }
            注意,这里由于是第一次启动应用程序的Activity,所以下面语句:

    ProcessRecord app = mService.getProcessRecordLocked(r.processName,
    	r.info.applicationInfo.uid);
            取回来的app为null。在Activity应用程序中的AndroidManifest.xml配置文件中,我们没有指定Application标签的process属性,系统就会默认使用package的名称,这里就是"shy.luo.activity"了。每一个应用程序都有自己的uid,因此,这里uid + process的组合就可以为每一个应用程序创建一个ProcessRecord。当然,我们可以配置两个应用程序具有相同的uid和package,或者在AndroidManifest.xml配置文件的application标签或者activity标签中显式指定相同的process属性值,这样,不同的应用程序也可以在同一个进程中启动。

           函数最终执行ActivityManagerService.startProcessLocked函数进行下一步操作。

           Step 23. ActivityManagerService.startProcessLocked

           这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityManagerService.java文件中:

    public final class ActivityManagerService extends ActivityManagerNative
    		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    
    	......
    
    	final ProcessRecord startProcessLocked(String processName,
    			ApplicationInfo info, boolean knownToBeDead, int intentFlags,
    			String hostingType, ComponentName hostingName, boolean allowWhileBooting) {
    
    		ProcessRecord app = getProcessRecordLocked(processName, info.uid);
    		
    		......
    
    		String hostingNameStr = hostingName != null
    			? hostingName.flattenToShortString() : null;
    
    		......
    
    		if (app == null) {
    			app = new ProcessRecordLocked(null, info, processName);
    			mProcessNames.put(processName, info.uid, app);
    		} else {
    			// If this is a new package in the process, add the package to the list
    			app.addPackage(info.packageName);
    		}
    
    		......
    
    		startProcessLocked(app, hostingType, hostingNameStr);
    		return (app.pid != 0) ? app : null;
    	}
    
    	......
    
    }
            这里再次检查是否已经有以process + uid命名的进程存在,在我们这个情景中,返回值app为null,因此,后面会创建一个ProcessRecord,并存保存在成员变量mProcessNames中,最后,调用另一个startProcessLocked函数进一步操作:

    public final class ActivityManagerService extends ActivityManagerNative
    		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    
    	......
    
    	private final void startProcessLocked(ProcessRecord app,
    				String hostingType, String hostingNameStr) {
    
    		......
    
    		try {
    			int uid = app.info.uid;
    			int[] gids = null;
    			try {
    				gids = mContext.getPackageManager().getPackageGids(
    					app.info.packageName);
    			} catch (PackageManager.NameNotFoundException e) {
    				......
    			}
    			
    			......
    
    			int debugFlags = 0;
    			
    			......
    			
    			int pid = Process.start("android.app.ActivityThread",
    				mSimpleProcessManagement ? app.processName : null, uid, uid,
    				gids, debugFlags, null);
    			
    			......
    
    		} catch (RuntimeException e) {
    			
    			......
    
    		}
    	}
    
    	......
    
    }
            这里主要是调用Process.start接口来创建一个新的进程,新的进程会导入android.app.ActivityThread类,并且执行它的main函数,这就是为什么我们前面说每一个应用程序都有一个ActivityThread实例来对应的原因。

            Step 24. ActivityThread.main

            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    
    	......
    
    	private final void attach(boolean system) {
    		......
    
    		mSystemThread = system;
    		if (!system) {
    
    			......
    
    			IActivityManager mgr = ActivityManagerNative.getDefault();
    			try {
    				mgr.attachApplication(mAppThread);
    			} catch (RemoteException ex) {
    			}
    		} else {
    
    			......
    
    		}
    	}
    
    	......
    
    	public static final void main(String[] args) {
    		
    		.......
    
    		ActivityThread thread = new ActivityThread();
    		thread.attach(false);
    
    		......
    
    		Looper.loop();
    
    		.......
    
    		thread.detach();
    		
    		......
    	}
    }
           这个函数在进程中创建一个ActivityThread实例,然后调用它的attach函数,接着就进入消息循环了,直到最后进程退出。

           函数attach最终调用了ActivityManagerService的远程接口ActivityManagerProxy的attachApplication函数,传入的参数是mAppThread,这是一个ApplicationThread类型的Binder对象,它的作用是用来进行进程间通信的。

          Step 25. ActivityManagerProxy.attachApplication

          这个函数定义在frameworks/base/core/java/android/app/ActivityManagerNative.java文件中:

    class ActivityManagerProxy implements IActivityManager
    {
    	......
    
    	public void attachApplication(IApplicationThread app) throws RemoteException
    	{
    		Parcel data = Parcel.obtain();
    		Parcel reply = Parcel.obtain();
    		data.writeInterfaceToken(IActivityManager.descriptor);
    		data.writeStrongBinder(app.asBinder());
    		mRemote.transact(ATTACH_APPLICATION_TRANSACTION, data, reply, 0);
    		reply.readException();
    		data.recycle();
    		reply.recycle();
    	}
    
    	......
    
    }
           这里通过Binder驱动程序,最后进入ActivityManagerService的attachApplication函数中。

           Step 26. ActivityManagerService.attachApplication

           这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityManagerService.java文件中:

    public final class ActivityManagerService extends ActivityManagerNative
    		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    
    	......
    
    	public final void attachApplication(IApplicationThread thread) {
    		synchronized (this) {
    			int callingPid = Binder.getCallingPid();
    			final long origId = Binder.clearCallingIdentity();
    			attachApplicationLocked(thread, callingPid);
    			Binder.restoreCallingIdentity(origId);
    		}
    	}
    
    	......
    
    }
            这里将操作转发给attachApplicationLocked函数。

            Step 27. ActivityManagerService.attachApplicationLocked

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityManagerService.java文件中:

    public final class ActivityManagerService extends ActivityManagerNative
    		implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    
    	......
    
    	private final boolean attachApplicationLocked(IApplicationThread thread,
    			int pid) {
    		// Find the application record that is being attached...  either via
    		// the pid if we are running in multiple processes, or just pull the
    		// next app record if we are emulating process with anonymous threads.
    		ProcessRecord app;
    		if (pid != MY_PID && pid >= 0) {
    			synchronized (mPidsSelfLocked) {
    				app = mPidsSelfLocked.get(pid);
    			}
    		} else if (mStartingProcesses.size() > 0) {
    			......
    		} else {
    			......
    		}
    
    		if (app == null) {
    			......
    			return false;
    		}
    
    		......
    
    		String processName = app.processName;
    		try {
    			thread.asBinder().linkToDeath(new AppDeathRecipient(
    				app, pid, thread), 0);
    		} catch (RemoteException e) {
    			......
    			return false;
    		}
    
    		......
    
    		app.thread = thread;
    		app.curAdj = app.setAdj = -100;
    		app.curSchedGroup = Process.THREAD_GROUP_DEFAULT;
    		app.setSchedGroup = Process.THREAD_GROUP_BG_NONINTERACTIVE;
    		app.forcingToForeground = null;
    		app.foregroundServices = false;
    		app.debugging = false;
    
    		......
    
    		boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);
    
    		......
    
    		boolean badApp = false;
    		boolean didSomething = false;
    
    		// See if the top visible activity is waiting to run in this process...
    		ActivityRecord hr = mMainStack.topRunningActivityLocked(null);
    		if (hr != null && normalMode) {
    			if (hr.app == null && app.info.uid == hr.info.applicationInfo.uid
    				&& processName.equals(hr.processName)) {
    					try {
    						if (mMainStack.realStartActivityLocked(hr, app, true, true)) {
    							didSomething = true;
    						}
    					} catch (Exception e) {
    						......
    					}
    			} else {
    				......
    			}
    		}
    
    		......
    
    		return true;
    	}
    
    	......
    
    }

            在前面的Step 23中,已经创建了一个ProcessRecord,这里首先通过pid将它取回来,放在app变量中,然后对app的其它成员进行初始化,最后调用mMainStack.realStartActivityLocked执行真正的Activity启动操作。这里要启动的Activity通过调用mMainStack.topRunningActivityLocked(null)从堆栈顶端取回来,这时候在堆栈顶端的Activity就是MainActivity了。

            Step 28. ActivityStack.realStartActivityLocked

            这个函数定义在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中:

    public class ActivityStack {
    
    	......
    
    	final boolean realStartActivityLocked(ActivityRecord r,
    			ProcessRecord app, boolean andResume, boolean checkConfig)
    			throws RemoteException {
    		
    		......
    
    		r.app = app;
    
    		......
    
    		int idx = app.activities.indexOf(r);
    		if (idx < 0) {
    			app.activities.add(r);
    		}
    		
    		......
    
    		try {
    			......
    
    			List<ResultInfo> results = null;
    			List<Intent> newIntents = null;
    			if (andResume) {
    				results = r.results;
    				newIntents = r.newIntents;
    			}
    	
    			......
    			
    			app.thread.scheduleLaunchActivity(new Intent(r.intent), r,
    				System.identityHashCode(r),
    				r.info, r.icicle, results, newIntents, !andResume,
    				mService.isNextTransitionForward());
    
    			......
    
    		} catch (RemoteException e) {
    			......
    		}
    
    		......
    
    		return true;
    	}
    
    	......
    
    }
            这里最终通过app.thread进入到ApplicationThreadProxy的scheduleLaunchActivity函数中,注意,这里的第二个参数r,是一个ActivityRecord类型的Binder对象,用来作来这个Activity的token值。

            Step 29. ApplicationThreadProxy.scheduleLaunchActivity
            这个函数定义在frameworks/base/core/java/android/app/ApplicationThreadNative.java文件中:

    class ApplicationThreadProxy implements IApplicationThread {
    
    	......
    
    	public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
    			ActivityInfo info, Bundle state, List<ResultInfo> pendingResults,
    			List<Intent> pendingNewIntents, boolean notResumed, boolean isForward)
    			throws RemoteException {
    		Parcel data = Parcel.obtain();
    		data.writeInterfaceToken(IApplicationThread.descriptor);
    		intent.writeToParcel(data, 0);
    		data.writeStrongBinder(token);
    		data.writeInt(ident);
    		info.writeToParcel(data, 0);
    		data.writeBundle(state);
    		data.writeTypedList(pendingResults);
    		data.writeTypedList(pendingNewIntents);
    		data.writeInt(notResumed ? 1 : 0);
    		data.writeInt(isForward ? 1 : 0);
    		mRemote.transact(SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION, data, null,
    			IBinder.FLAG_ONEWAY);
    		data.recycle();
    	}
    
    	......
    
    }
            这个函数最终通过Binder驱动程序进入到ApplicationThread的scheduleLaunchActivity函数中。

            Step 30. ApplicationThread.scheduleLaunchActivity
            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    
    	......
    
    	private final class ApplicationThread extends ApplicationThreadNative {
    
    		......
    
    		// we use token to identify this activity without having to send the
    		// activity itself back to the activity manager. (matters more with ipc)
    		public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
    				ActivityInfo info, Bundle state, List<ResultInfo> pendingResults,
    				List<Intent> pendingNewIntents, boolean notResumed, boolean isForward) {
    			ActivityClientRecord r = new ActivityClientRecord();
    
    			r.token = token;
    			r.ident = ident;
    			r.intent = intent;
    			r.activityInfo = info;
    			r.state = state;
    
    			r.pendingResults = pendingResults;
    			r.pendingIntents = pendingNewIntents;
    
    			r.startsNotResumed = notResumed;
    			r.isForward = isForward;
    
    			queueOrSendMessage(H.LAUNCH_ACTIVITY, r);
    		}
    
    		......
    
    	}
    
    	......
    }
             函数首先创建一个ActivityClientRecord实例,并且初始化它的成员变量,然后调用ActivityThread类的queueOrSendMessage函数进一步处理。

             Step 31. ActivityThread.queueOrSendMessage
             这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    
    	......
    
    	private final class ApplicationThread extends ApplicationThreadNative {
    
    		......
    
    		// if the thread hasn't started yet, we don't have the handler, so just
    		// save the messages until we're ready.
    		private final void queueOrSendMessage(int what, Object obj) {
    			queueOrSendMessage(what, obj, 0, 0);
    		}
    
    		......
    
    		private final void queueOrSendMessage(int what, Object obj, int arg1, int arg2) {
    			synchronized (this) {
    				......
    				Message msg = Message.obtain();
    				msg.what = what;
    				msg.obj = obj;
    				msg.arg1 = arg1;
    				msg.arg2 = arg2;
    				mH.sendMessage(msg);
    			}
    		}
    
    		......
    
    	}
    
    	......
    }
            函数把消息内容放在msg中,然后通过mH把消息分发出去,这里的成员变量mH我们在前面已经见过,消息分发出去后,最后会调用H类的handleMessage函数。

            Step 32. H.handleMessage

            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    
    	......
    
    	private final class H extends Handler {
    
    		......
    
    		public void handleMessage(Message msg) {
    			......
    			switch (msg.what) {
    			case LAUNCH_ACTIVITY: {
    				ActivityClientRecord r = (ActivityClientRecord)msg.obj;
    
    				r.packageInfo = getPackageInfoNoCheck(
    					r.activityInfo.applicationInfo);
    				handleLaunchActivity(r, null);
    			} break;
    			......
    			}
    
    		......
    
    	}
    
    	......
    }
            这里最后调用ActivityThread类的handleLaunchActivity函数进一步处理。

            Step 33. ActivityThread.handleLaunchActivity

            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    
    	......
    
    	private final void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {
    		......
    
    		Activity a = performLaunchActivity(r, customIntent);
    
    		if (a != null) {
    			r.createdConfig = new Configuration(mConfiguration);
    			Bundle oldState = r.state;
    			handleResumeActivity(r.token, false, r.isForward);
    
    			......
    		} else {
    			......
    		}
    	}
    
    	......
    }
            这里首先调用performLaunchActivity函数来加载这个Activity类,即shy.luo.activity.MainActivity,然后调用它的onCreate函数,最后回到handleLaunchActivity函数时,再调用handleResumeActivity函数来使这个Activity进入Resumed状态,即会调用这个Activity的onResume函数,这是遵循Activity的生命周期的。

            Step 34. ActivityThread.performLaunchActivity
            这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中:

    public final class ActivityThread {
    
    	......
    
    	private final Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
    		
    		ActivityInfo aInfo = r.activityInfo;
    		if (r.packageInfo == null) {
    			r.packageInfo = getPackageInfo(aInfo.applicationInfo,
    				Context.CONTEXT_INCLUDE_CODE);
    		}
    
    		ComponentName component = r.intent.getComponent();
    		if (component == null) {
    			component = r.intent.resolveActivity(
    				mInitialApplication.getPackageManager());
    			r.intent.setComponent(component);
    		}
    
    		if (r.activityInfo.targetActivity != null) {
    			component = new ComponentName(r.activityInfo.packageName,
    				r.activityInfo.targetActivity);
    		}
    
    		Activity activity = null;
    		try {
    			java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
    			activity = mInstrumentation.newActivity(
    				cl, component.getClassName(), r.intent);
    			r.intent.setExtrasClassLoader(cl);
    			if (r.state != null) {
    				r.state.setClassLoader(cl);
    			}
    		} catch (Exception e) {
    			......
    		}
    
    		try {
    			Application app = r.packageInfo.makeApplication(false, mInstrumentation);
    
    			......
    
    			if (activity != null) {
    				ContextImpl appContext = new ContextImpl();
    				appContext.init(r.packageInfo, r.token, this);
    				appContext.setOuterContext(activity);
    				CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
    				Configuration config = new Configuration(mConfiguration);
    				......
    				activity.attach(appContext, this, getInstrumentation(), r.token,
    					r.ident, app, r.intent, r.activityInfo, title, r.parent,
    					r.embeddedID, r.lastNonConfigurationInstance,
    					r.lastNonConfigurationChildInstances, config);
    
    				if (customIntent != null) {
    					activity.mIntent = customIntent;
    				}
    				r.lastNonConfigurationInstance = null;
    				r.lastNonConfigurationChildInstances = null;
    				activity.mStartedActivity = false;
    				int theme = r.activityInfo.getThemeResource();
    				if (theme != 0) {
    					activity.setTheme(theme);
    				}
    
    				activity.mCalled = false;
    				mInstrumentation.callActivityOnCreate(activity, r.state);
    				......
    				r.activity = activity;
    				r.stopped = true;
    				if (!r.activity.mFinished) {
    					activity.performStart();
    					r.stopped = false;
    				}
    				if (!r.activity.mFinished) {
    					if (r.state != null) {
    						mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
    					}
    				}
    				if (!r.activity.mFinished) {
    					activity.mCalled = false;
    					mInstrumentation.callActivityOnPostCreate(activity, r.state);
    					if (!activity.mCalled) {
    						throw new SuperNotCalledException(
    							"Activity " + r.intent.getComponent().toShortString() +
    							" did not call through to super.onPostCreate()");
    					}
    				}
    			}
    			r.paused = true;
    
    			mActivities.put(r.token, r);
    
    		} catch (SuperNotCalledException e) {
    			......
    
    		} catch (Exception e) {
    			......
    		}
    
    		return activity;
    	}
    
    	......
    }

           函数前面是收集要启动的Activity的相关信息,主要package和component信息:

       ActivityInfo aInfo = r.activityInfo;
       if (r.packageInfo == null) {
            r.packageInfo = getPackageInfo(aInfo.applicationInfo,
                    Context.CONTEXT_INCLUDE_CODE);
       }
    
       ComponentName component = r.intent.getComponent();
       if (component == null) {
           component = r.intent.resolveActivity(
               mInitialApplication.getPackageManager());
           r.intent.setComponent(component);
       }
    
       if (r.activityInfo.targetActivity != null) {
           component = new ComponentName(r.activityInfo.packageName,
                   r.activityInfo.targetActivity);
       }
           然后通过ClassLoader将shy.luo.activity.MainActivity类加载进来:

       Activity activity = null;
       try {
    	java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
    	activity = mInstrumentation.newActivity(
    		cl, component.getClassName(), r.intent);
    	r.intent.setExtrasClassLoader(cl);
    	if (r.state != null) {
    		r.state.setClassLoader(cl);
    	}
       } catch (Exception e) {
    	......
       }
          接下来是创建Application对象,这是根据AndroidManifest.xml配置文件中的Application标签的信息来创建的:

       Application app = r.packageInfo.makeApplication(false, mInstrumentation);
          后面的代码主要创建Activity的上下文信息,并通过attach方法将这些上下文信息设置到MainActivity中去:

       activity.attach(appContext, this, getInstrumentation(), r.token,
    	r.ident, app, r.intent, r.activityInfo, title, r.parent,
    	r.embeddedID, r.lastNonConfigurationInstance,
    	r.lastNonConfigurationChildInstances, config);
          最后还要调用MainActivity的onCreate函数:

       mInstrumentation.callActivityOnCreate(activity, r.state);
          这里不是直接调用MainActivity的onCreate函数,而是通过mInstrumentation的callActivityOnCreate函数来间接调用,前面我们说过,mInstrumentation在这里的作用是监控Activity与系统的交互操作,相当于是系统运行日志。

          Step 35. MainActivity.onCreate

          这个函数定义在packages/experimental/Activity/src/shy/luo/activity/MainActivity.java文件中,这是我们自定义的app工程文件:

    public class MainActivity extends Activity  implements OnClickListener {
    	
    	......
    
    	@Override
    	public void onCreate(Bundle savedInstanceState) {
    		......
    
    		Log.i(LOG_TAG, "Main Activity Created.");
    	}
    
    	......
    
    }
           这样,MainActivity就启动起来了,整个应用程序也启动起来了。

           整个应用程序的启动过程要执行很多步骤,但是整体来看,主要分为以下五个阶段:

           一. Step1 - Step 11:Launcher通过Binder进程间通信机制通知ActivityManagerService,它要启动一个Activity;

           二. Step 12 - Step 16:ActivityManagerService通过Binder进程间通信机制通知Launcher进入Paused状态;

           三. Step 17 - Step 24:Launcher通过Binder进程间通信机制通知ActivityManagerService,它已经准备就绪进入Paused状态,于是ActivityManagerService就创建一个新的进程,用来启动一个ActivityThread实例,即将要启动的Activity就是在这个ActivityThread实例中运行;

           四. Step 25 - Step 27:ActivityThread通过Binder进程间通信机制将一个ApplicationThread类型的Binder对象传递给ActivityManagerService,以便以后ActivityManagerService能够通过这个Binder对象和它进行通信;

           五. Step 28 - Step 35:ActivityManagerService通过Binder进程间通信机制通知ActivityThread,现在一切准备就绪,它可以真正执行Activity的启动操作了。

           这里不少地方涉及到了Binder进程间通信机制,相关资料请参考Android进程间通信(IPC)机制Binder简要介绍和学习计划一文。

           这样,应用程序的启动过程就介绍完了,它实质上是启动应用程序的默认Activity,在下一篇文章中,我们将介绍在应用程序内部启动另一个Activity的过程,即新的Activity与启动它的Activity将会在同一个进程(Process)和任务(Task)运行,敬请关注。

    老罗的新浪微博:http://weibo.com/shengyangluo,欢迎关注!

    展开全文
  • 如何查找源代码

    千次阅读 2009-12-11 15:37:00
    E.g: 找reiserfsck源代码 localhost:/ # which reiserfsck /sbin/reiserfscklocalhost:/ # rpm -qf /sbin/reiserfsck reiserfs-3.6.19-19.12localhost:/ # 几个查找源代码的好网站 http://rpm.pbone.net/ ...

    E.g: 找reiserfsck源代码

     

    localhost:/ # which reiserfsck
    /sbin/reiserfsck
    localhost:/ # rpm -qf /sbin/reiserfsck
    reiserfs-3.6.19-19.12
    localhost:/ #

     

    几个查找源代码的好网站

     http://rpm.pbone.net/
     http://rpmfind.com/
     http://www.rpmfind.net/

     

    在这些网站上找reiserfs就可以了,要带src就是源代码了!

    展开全文
  • 查找论文源代码网站

    万次阅读 2019-03-18 16:17:21
  • 二分查找源代码

    千次阅读 2012-02-08 09:10:14
    DWORD IN_pArray[], 待查找数组 DWORD IN_ArrayNum, 数组大小 DWORD Value 待匹配数据 返回: 0xffffffff 查找识别 0-IN_ArrayNum-1 匹配成功,返回位置 */ DWORD BinarySearch(DWORD IN_pArray[],DWORD IN_...
    /*
    对折法
    
    参数:
    DWORD IN_pArray[],  待查找数组
    DWORD IN_ArrayNum,  数组大小
    DWORD Value         待匹配数据
    
    返回:
    0xffffffff 查找识别
    0-IN_ArrayNum-1 匹配成功,返回位置
    */
    DWORD BinarySearch(DWORD IN_pArray[],DWORD IN_ArrayNum,DWORD Value ) 
    {
    	//首先判断是否在数组中
    	if( (Value<IN_pArray[0]) || (Value>IN_pArray[IN_ArrayNum-1]) ) return 0xffffffff;
    
    	//数组头指针
    	DWORD *pArray=IN_pArray;
    	//元素个数
    	DWORD Num=IN_ArrayNum;
    	DWORD Temp;
    
    	//对折循环
    	//元素个数为1时,无需对折
    	while( Num>1 )
    	{
    		//数量直接右移
    		Temp=Num>>1;
    
    		//是否在数组右半部
    		if( pArray[Temp]<Value )
    		{
    			pArray+=Temp+1;
    			Num-=Temp+1;
    		}
    		//是否在数组左半部
    		else if( pArray[Temp]>Value )
    		{
    			Num=Temp;
    		}
    		//匹配成功
    		else
    		{
    			//返回位置
    			return pArray+Temp-IN_pArray;
    		}
    	}
    	//对折循环--End
    
    	//当元素个数为1是判断是否匹配,返回位置
    	if( pArray[0]==Value ) return pArray-IN_pArray;
    
    	return 0xffffffff;
    }
    
    


    展开全文
  • 如何查找论文的源代码

    万次阅读 多人点赞 2020-04-13 12:38:58
    介绍两个用于查询论文源代码的网站并介绍一些常用的获取code的办法 1、https://paperswithcode.com/ 操作如下图所示,左上角输入名字,便会出来结果,然后点击code部分即可 2、...
  • 查找OpenCV里的函数源代码

    千次阅读 2017-10-01 12:54:01
    1找到Opencv的安装目录,例如我的安装目录在D盘,找到相应的安装目录如下所示   2可以看到上图中有两个目录文件夹,而我们要找的...4下面我们以查找Opencv中图像处理函数cameracalibration()的源代码为例,它存在ca
  • GDB源代码查找路径

    千次阅读 2018-07-13 10:47:32
    转自:https://www.cnblogs.com/rickyk/p/4184860.html在gdb程序的时候,有时候会发现源代码文件找不到,对于那些带调试信息的系统库或者第三方库,很多时候当你真正想gdb去追他源代码的时候你会发现gdb根本找不到...
  • 打印自身源代码程序

    千次阅读 2016-09-16 10:56:55
    任意选定一个语言写一个打印自身源代码程序,这个程序不允许读取或者写其他文件的数据,程序必须是完全独立的。 很有趣吧?我正在学习C语言,这个问题是我在查找其他资料时看到的,这激发了我的兴趣,我躺在...
  • 如何快速查找论文的源代码

    千次阅读 多人点赞 2020-10-25 11:33:09
    写在这里的初衷,一是备忘,二是希望得到高人指点,三是希望能遇到志同道合的朋友。...rstoj 做的一个网站,将 ArXiv 上的最新机器学习论文与 Github 上的代码(TensorFlow/PyTorch/MXNet/等)对应...如何查找论文的源代码
  • 源代码生成可执行程序过程

    千次阅读 2018-02-01 21:41:19
    问:经常敲代码,代码是如何生成可执行程序的?... 1)第一步:预处理器扩展源代码—–展开头文件(#include命令包含文件),#define定义标识符的替换,去除注释 2)第二步:编译器产生两个源文件的汇编代
  • 微信小程序源代码_下厨房菜谱APP

    千次阅读 2016-11-08 20:24:16
    源代码下载地址: http://pan.baidu.com/s/1nv8m1ip基于微信小程序的一个查找检索菜谱的应用功能分类检索菜谱 发现最新菜谱 根据菜谱名搜索菜谱 用到的API页面路由 列表渲染 带参数页面跳转 navigator ...
  • 如何从在安卓Android手机获取微信小程序源代码

    千次阅读 热门讨论 2020-02-12 21:28:37
    如何从在安卓Android手机获取微信小程序源代码 获取微信小程序源代码两种方法: 1、在手机中获取。但需要获取手机的root权限,获得微信小程序的wxapkg包; 2、运用模拟器,在电脑上运行微信小程序,获得微信小程序的...
  • live555 源代码简单分析1:主程序

    万次阅读 2013-09-25 17:36:24
    live555源代码有以下几个明显的特点: 1.头文件是.hh后缀的,但没觉得和.h后缀的有什么不同 2.采用了面向对象的程序设计思路,里面各种对象   好了,不罗嗦,使用vc2010打开live555的vc工程,看到live555源代码结构...
  • 在进行开发时,我们可能需要知道手机上某些服务,如短信和联系人等等的provider 中的主机名 ,因此需要使用GIT工具下载安卓程序源代码,以下是简单的介绍: GIT工具下载地址: ...获取源代码步骤: ...
  • 如何查找一篇论文的源代码

    千次阅读 2020-11-20 10:48:27
    作者:Jason Gu ...来源:知乎 著作权归作者所有。商业转载请联系作者获得授权,非商业转载请注明出处。 经典论文,经典算法。...查看该论文的被引用论文,其作者有时会将自己算法与引用算法比较,有可能手上会有这个代
  • 算法思想:在表的一端设置一个称为“监视哨”的附加单元,存放要查找元素的关键字,从表的另一端开始查找,如果在“监视哨”找到要查找元素的关键字,返回失败信息,否则,返回相应下标。
  • 源代码到可执行程序

    千次阅读 2018-04-06 09:47:56
    源代码 hello.c, 利用hexdump命令,可以看下hello.c到底是什么? 一串的二进制文件(用16进制表示),编码采用的是ASCII编码(二进制和字符之间的对应关系),通过下表,可以将hello.c中的字符和二进制对应起来,...
  • 算法思想: 首先,将表中间位置记录的关键字与查找关键字比较,如果两者相等,则查找成功;否则利用中间位置记录将表分成前、后两个子表,如果中间位置记录的关键字大于查找关键字,则进一步查找前一子表,否则...
  • 通过前面的学习,我们知道在Android系统中,Content Provider可以为不同的应用程序访问相同的数据提供统一的入口。Content Provider一般是运行在独立的进程中的,每一个Content Provider在系统中只有一个实例存在,...
  • 在使用VS2008和Microsoft.Visual.SourceSafe...您无法使用此提供程序执行源代码管理操作”的提示框,而且也不能登录服务器源代码管理,但用 Microsoft.Visual.SourceSafe时可以登录服务器源代码管理,但获取最新版本
  • 如果以下站点失效,你可以尝试在Google中输入如下内容进行查找: inurl:"mysql" /Downloads/ intitle:"index" of "mysql/" 收集开源数据库MySQL源代码及安装程序镜像站点,镜像内容包括了MySQL从3.23...
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  • ABAP中查找代码的标准程序

    千次阅读 2018-06-11 20:15:15
    RPR_ABAP_SOURCE_SCAN 可以用于搜索SAP中的程序代码,一般使用时填写开发类、程序名及需要查找的字符串即可,选择屏幕布局和功能很简单,熟悉ABAP代码的人一看就明白了,不多解释了,使用方法及截图如下。...
  • 主要功能包括图书数据的录入、查找、修改、删除、统计、排序等。 要求:1)图书数据有多条书目构成,信息包括序号、书名、作者、出版社、...每次操作都从该菜单选择,利用循环结构使得一次运行程序可进行多次操作。
  • 这是很久以前回答人家一道关于使用 VB 捆绑木马的问题,...待程序运行时先把杀毒软件的进程给KILL掉,然后再把它释放出来,效果很好,并且杀毒软件也查不到,以下是我的程序源代码。里面还有很多与它不相关的代码,我
  • 打开sql2005,突然弹出一个这样的错误:初始化 Microsoft Visual SourceSafe 源代码管理提供程序时失败。您无法使用此提供程序执行源代码管理操作。还以为数据库出了什么问题,要重装就麻烦了。上网一查,原来...
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    千次阅读 2019-07-10 15:50:48
  • 基于源代码的增强

    千次阅读 2015-11-10 22:17:36
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  • c#做的仿 QQ2010 聊天程序源代码

    千次阅读 2010-09-09 02:15:00
    <br />1. 登录界面 <br />2. 网络设置 <br />3.... 登录中 <br />6. 登录成功主界面 <br />7.... 查找/添加好友 <br /> 11. 主菜单 <br />用到的界面控件本人已做

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