提示 Canvas don 't allow drawing错误

luo_342815 2010-06-21 03:24:38

这个错误如何解决？这个错误有的时候发生得早，有的时候过一端时间发生。发生以后就不工作了。编译又没错。

 For i:=0 to 200+lineh*10 do begin  //循环显示相关信息   /

      if PThreadStart then//PThreadStart  =true;

      begin

          if i=150 then sleep(3000);



          main.Paintbox1.Canvas.Lock;



          main.Paintbox1.Canvas.TextOut(5,155+-i,'最新进出场站公交信息:');



          main.Paintbox1.Canvas.TextOut(10,155+lineh*2-i,'车辆信息:');



          main.Paintbox1.Canvas.TextOut(300,155+lineh*2-i,'驾驶员信息:');



          main.Paintbox1.Canvas.TextOut(10,155+lineh*4-i,'车牌:'+Plate);



          main.Paintbox1.Canvas.TextOut(300,155+lineh*4-i,'姓名:'+WorkerName+'  性别:'+Sex+'  工号:'+WorkID);



          main.Paintbox1.Canvas.TextOut(10,155+lineh*6-i,'车型:'+BusStyle);



          main.Paintbox1.Canvas.TextOut(300,155+lineh*6-i,'年龄:'+Age+'       工龄:'+Seniority);



          main.Paintbox1.Canvas.TextOut(10,155+lineh*8-i,'时间:'+OperateTime+'      状态:'+OperateStyle);



          main.Paintbox1.Canvas.TextOut(300,155+lineh*8-i,'联系电话:'+Telephone);



          main.Paintbox1.Canvas.TextOut(10,155+lineh*9-i,'                            ');

          sleep(20);



          end;

      end

      else

      begin

          main.Paintbox1.Invalidate;



          exit;

      end;

    end;

...全文

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luo_342815 2010-06-22

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谢谢大家。

nanchangfantasy 2010-06-22

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delphi线程是不受保护的,你要坚信用synchronize,或则用criticalsection来同步
否则肯定会有很多莫名的隐患.
只要把这段代码放到synchronize执行,该能没事的.
将如下放到synchronize
main.Paintbox1.Canvas.TextOut(5,155+-i,'最新进出场站公交信息:');

main.Paintbox1.Canvas.TextOut(10,155+lineh*2-i,'车辆信息:');

main.Paintbox1.Canvas.TextOut(300,155+lineh*2-i,'驾驶员信息:');

main.Paintbox1.Canvas.TextOut(10,155+lineh*4-i,'车牌:'+Plate);

main.Paintbox1.Canvas.TextOut(300,155+lineh*4-i,'姓名:'+WorkerName+' 性别:'+Sex+' 工号:'+WorkID);

main.Paintbox1.Canvas.TextOut(10,155+lineh*6-i,'车型:'+BusStyle);

main.Paintbox1.Canvas.TextOut(300,155+lineh*6-i,'年龄:'+Age+' 工龄:'+Seniority);

main.Paintbox1.Canvas.TextOut(10,155+lineh*8-i,'时间:'+OperateTime+' 状态:'+OperateStyle);

main.Paintbox1.Canvas.TextOut(300,155+lineh*8-i,'联系电话:'+Telephone);

main.Paintbox1.Canvas.TextOut(10,155+lineh*9-i,' ');
main.Paintbox1.Canvas.Unlock ;

cngoodman 2010-06-21

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main.Paintbox1.Canvas.Unlock 呢？

taxi 2010-06-21

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把while里面的代码放到synchronize中，sleep(1000)放在while循环里面。

taxi 2010-06-21

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要放到synchronize中画，把 sleep(1000)放在while循环里面。

luo_342815 2010-06-21

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这个是整个线程函数。不用synchronize的好像运行还可以，就是不大稳定。用了synchronize就卡在那里了。加了 application.ProcessMessages 效果也不提高不了多少。象这种一直要修改界面的情况，用synchronize不大合适吧？



procedure PaintThread.Execute;

var lineh,i:integer;

begin

  ReRead:=true;

  sleep(1000);

  while PThreadStart do

  begin



    if ReRead then

    begin

      with DM.DM1.AQ3 do

      begin

          close;

          sql.clear;

          sql.add('select top 1 ID,WorkID,WorkerEPC,WorkerName,WorkerAge,WorkerTelephone,'+

          'WorkerSeniority,WorkerSex,Plate,BusEPC,BusYearUsed,BusStyle,OperateTime,OperateStyle from IOMessage order by ID DESC');

          open;

          if recordcount<>0 then

          begin

            Plate:=fieldbyname('Plate').AsString;

            BusStyle:=fieldbyname('BusStyle').AsString;

            YearUsed:=fieldbyname('BusYearUsed').AsString;

            OperateTime:=fieldbyname('OperateTime').AsString;

            OperateStyle:=fieldbyname('OperateStyle').AsString;



            WorkID:=fieldbyname('WorkID').AsString;

            WorkerName:=fieldbyname('WorkerName').AsString;

            Age:=fieldbyname('WorkerAge').AsString;

            Sex:=fieldbyname('WorkerSex').AsString;

            Seniority:=fieldbyname('WorkerSeniority').AsString;

            Telephone:=fieldbyname('WorkerTelephone').AsString;

          end;

      end;

      ReRead:=false;

    end;

    lineh:=main.Paintbox1.Canvas.TextHeight('0'); //求字符的高度

 For i:=0 to 200+lineh*10 do begin  //循环显示相关信息   /

      if PThreadStart then

      begin

          if i=150 then sleep(3000);

          main.Paintbox1.Canvas.TextOut(5,155+-i,'最新进出场站公交信息:');

          main.Paintbox1.Canvas.TextOut(10,155+lineh*2-i,'车辆信息:');



          main.Paintbox1.Canvas.TextOut(300,155+lineh*2-i,'驾驶员信息:');



          main.Paintbox1.Canvas.TextOut(10,155+lineh*4-i,'车牌:'+Plate);



          main.Paintbox1.Canvas.TextOut(300,155+lineh*4-i,'姓名:'+WorkerName+'  性别:'+Sex+'  工号:'+WorkID);



          main.Paintbox1.Canvas.TextOut(10,155+lineh*6-i,'车型:'+BusStyle);



          main.Paintbox1.Canvas.TextOut(300,155+lineh*6-i,'年龄:'+Age+'       工龄:'+Seniority);



          main.Paintbox1.Canvas.TextOut(10,155+lineh*8-i,'时间:'+OperateTime+'      状态:'+OperateStyle);



          main.Paintbox1.Canvas.TextOut(300,155+lineh*8-i,'联系电话:'+Telephone);



          main.Paintbox1.Canvas.TextOut(10,155+lineh*9-i,'                                                                   ');

          //

          Delay(0,1);

      end

      else

      begin

          main.Paintbox1.Invalidate;



          exit;

      end;

    end;

  end;

end;