效果图：





1.定义一个Spinner控件：


<Spinner
    android:layout_width="150dp"
    android:layout_height="match_parent"
    android:id="@+id/spinner_car">



2.Activity代码：


Spinner spinner_car;

List<String> cars = new ArrayList<>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    spinner_car = findViewById(R.id.spinner_car);
    myadapter();
}

public void myadapter()
{
    cars.add("1号爪黄飞电");
    cars.add("2号卷毛赤兔");
    cars.add("3号绝影");
    cars.add("请选择车辆");
    Myadapter myadapter = new Myadapter(thisR.layout.support_simple_spinner_dropdown_item,cars);
    spinner_car.setAdapter(myadapter);
    //默认选中最后一项
    spinner_car.setSelection(cars.size()-1,true);
}

/**
 * 定义一个Myadapter类继承ArrayAdapter
 * 重写以下两个方法
 * */
class Myadapter<T> extends ArrayAdapter{
    public Myadapter(@NonNull Context context, int resource, @NonNull List<T> objects) {
        super(context, resource, objects);
    }

    @Override
    public int getCount() {
        //返回数据的统计数量，大于0项则减去1项，从而不显示最后一项
        int i = super.getCount();
        return i>0?i-1:i;
    }
}

Spinner控件可以监听，但是监听的话，如果两次点击都是同一个item的话，那么就就不会触发，因为看源码的话就会发现，在Spinner中有一个保存上次点击的位置的变量叫做 
mOldSelectedPosition的变量，每次点击的时候就会验证两次点击是否是同一个item，不同就触发点击事件，因此可以修改mOldSelectedPosition变量，让控件两次点击相同都可以触发。但是私有变量也可以改变他的值，就是使用java的反射来做。
以下就是源码部分：
  void checkSelectionChanged() {
        if ((mSelectedPosition != mOldSelectedPosition) || (mSelectedRowId != mOldSelectedRowId)) {
            selectionChanged();
            mOldSelectedPosition = mSelectedPosition;
            mOldSelectedRowId = mSelectedRowId;
        }
    }
方法checkSelectionChanged和变量mOldSelectedPosition都是AdapterView私有的，我们无法继承Spinner重写之。不过，利用java的反射，我们可以暴力修改mOldSelectedPosition的值：


new OnItemSelectedListener() {

		@Override
		public void onItemSelected(AdapterView<?> arg0, View arg1,
				int arg2, long arg3) {
			// TODO Auto-generated method stub
			try {
				//以下三行代码是解决问题所在
				Field field = AdapterView.class.getDeclaredField("mOldSelectedPosition");
				field.setAccessible(true);	//设置mOldSelectedPosition可访问
				field.setInt(spinner, AdapterView.INVALID_POSITION); //设置mOldSelectedPosition的值
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

		@Override
		public void onNothingSelected(AdapterView<?> arg0) {
			// TODO Auto-generated method stub
			
		}
	};

一个简单的安卓spinner控件自绘。外观可行，但实用性不怎么样。
控件分为两个部分：一个textview和一个popupwindow
textview自定义边框形状、边线，并在右边添加“﹀“”︿”图像，单击textview时弹出popupwindow




代码：
主活动中：

public class MainActivity extends Activity 
{
	private SpinerPopWindow<String> mSpinerPopWindow;
	private List<String> list = new ArrayList<String>();
	private TextView tvValue;


	@Override
	protected void onCreate(Bundle savedInstanceState) 
	{
		super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.activity_main);

list.add("test1:");
list.add("test2:");
list.add("test3:");
list.add("test4:");
list.add("test5:");
list.add("test6:");



		tvValue = (TextView) findViewById(R.id.tv_value);
		//显示PopupWindow
		tvValue.setOnClickListener(new OnClickListener() 
		{
			@Override
			public void onClick(View v) 
			{
				switch (v.getId()) 
				{
				case R.id.tv_value:
					mSpinerPopWindow.setWidth(tvValue.getWidth());
					mSpinerPopWindow.showAsDropDown(tvValue);
					setTextImage(R.drawable.icon_up);
					break;
				}
			}
		});
		//popupwindow显示的ListView的item点击事件
		mSpinerPopWindow = new SpinerPopWindow<String>(this, list,new OnItemClickListener() 
		{
			@Override
			public void onItemClick(AdapterView<?> parent, View view, int position,long id) 
			{
				mSpinerPopWindow.dismiss();
				tvValue.setText(list.get(position));
			}
		});
		//监听popupwindow取消
		mSpinerPopWindow.setOnDismissListener(new OnDismissListener()
		{
			@Override
			public void onDismiss() 
			{
				setTextImage(R.drawable.icon_down);
			}
		});
	}
	




	//设置右端图像
	private void setTextImage(int resId) 
	{
		Drawable drawable = getResources().getDrawable(resId);
		drawable.setBounds(0, 0, drawable.getMinimumWidth(),drawable.getMinimumHeight());// 必须设置图片大小，否则不显示
		tvValue.setCompoundDrawables(null, null, drawable, null);
	}
}


PopupWindow代码：


@SuppressWarnings("unused")
@SuppressLint("InflateParams") 
public class SpinerPopWindow<T> extends PopupWindow 
{
	private LayoutInflater inflater;
	private ListView mListView;
	private List<T> list;	
	private MyAdapter  mAdapter;
	
	public SpinerPopWindow(Context context,List<T> list,OnItemClickListener clickListener) 
	{
		super(context);
		inflater=LayoutInflater.from(context);
		this.list=list;
		init(clickListener);
	}
	
	
	private void init(OnItemClickListener clickListener)
	{
		View view = inflater.inflate(R.layout.spiner_window_layout, null);
		setContentView(view);		
		setWidth(LayoutParams.WRAP_CONTENT);
		setHeight(LayoutParams.WRAP_CONTENT);
		setFocusable(true);
    		ColorDrawable dw = new ColorDrawable(0x00);
		setBackgroundDrawable(dw);
		mListView = (ListView) view.findViewById(R.id.listview);
		mListView.setAdapter(mAdapter=new MyAdapter());
		mListView.setOnItemClickListener(clickListener);
	}
	
	private class MyAdapter extends BaseAdapter
	{
		@Override
		public int getCount() 
		{
			return list.size();
		}

		@Override
		public Object getItem(int position) 
		{
			return list.get(position);
		}

		@Override
		public long getItemId(int position) 
		{
			return position;
		}

		@SuppressWarnings("unchecked")
		@Override
		public View getView(int position, View convertView, ViewGroup parent) 
		{
			ViewHolder holder=null;
			if(convertView==null)
			{
				holder=new ViewHolder();
				convertView=inflater.inflate(R.layout.spiner_item_layout, null);
				holder.tvName=(TextView) convertView.findViewById(R.id.tv_name);
				convertView.setTag(holder);
			}
			else
			{
				holder=(ViewHolder) convertView.getTag();
			}
			holder.tvName.setText(getItem(position).toString());
			return convertView;
		}
	}
	
	private class ViewHolder
	{
		private TextView tvName;
	}
}


shape_list.xml


<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <!-- This is the main color -->
    <item>
        <shape>
            <!-- 边框颜色 -->
            <solid android:color="#71C297"/>
        </shape>
    </item>
    <!-- 给View的上 左  右设置8dp的边框 -->
    <item
        android:left="1dp"
        android:right="1dp"
        android:bottom="1dp">
        <shape>
            <!-- View填充颜色 -->
            <solid android:color="#FFFFFFFF"/>
        </shape>
    </item>

</layer-list>


shape_tv.xml


<shape xmlns:android="http://schemas.android.com/apk/res/android" >
    
    <!-- 填充的颜色 -->
    <solid android:color="#FFFFFFFF" />

    <corners
        android:topLeftRadius="5dp"
        android:topRightRadius="5dp" />
    <!-- 设置边框 -->
    <stroke
        android:width="1dp"
        android:color="#71C297" />

</shape>


spiner_window_layout.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:orientation="vertical">

    <ListView
        android:id="@+id/listview"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:cacheColorHint="#00000000"
        android:background="@drawable/shape_list"
        android:scrollbars="none" >
    </ListView>
</LinearLayout>


spiner_item_layout.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center_vertical">

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:textColor="#666666"
        android:textSize="20sp"/>

</LinearLayout>


actity_main.xml


<TextView
        android:id="@+id/tv_value"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:background="@drawable/shape_tv"//可以设置背景图片
        android:drawableRight="@drawable/icon_down"
        android:padding="10dp"
        android:text="请选择父类别"
        android:textColor="#666666"
        android:textSize="20sp" />

安卓界面控件之Spinner
Spinner的定义:
如果为Spinner中添加选择项目

Spinner的定义:
			1.Spinner是一种能够从多个选项中选一个选项的控件,使用浮动菜单为用户提供选择
			2.类似于桌面程序的组合框(ComboBox)
			
			Spinner位于工具栏Palette栏中的Containers中的第一个(意味着Spinner是一种容器,存放选择的容器)

如果为Spinner中添加选择项目
			List<String> list = new ArrayList<String>();//创建一个List数组存放spinner中下拉选项中的项目
    list.add("计算机科学与技术");//添加项目,其postion为0
    list.add("物联网");//添加项目,其postion为1
    list.add("软件工程");//添加项目,其postion为2

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,list);//创建一个适配器,this代指上下文即Mainactivity,item为下拉菜单的样式为系统内置,list为上文创建的list
    final Spinner spinnerOfPro = findViewById(R.id.spinnerOfPro);//关联XML文件中的Spinner控件spinnerOfPro
    
    spinnerOfPro.setAdapter(adapter);//关联适配器
    为选择项目添加事件
    spinnerOfPro.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            textViewOfProOut.setText("你的专业是:"+ spinnerOfPro.getItemAtPosition(position));
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }