what is the function of this expression :application.processmessage

lhh 您好 : 讓目前的 Application ,可以處理現在在 Message Queue 內的 Message... 通常在迴圈中需要執行較長的時間 (或 Busy Waiting)的時候使用,讓畫面不至於停滯像當機... PS. 幾位大大之前有幫您解答,您應該給分給有合適答案的大大們... ---- 我只會兩件事,這也不會,那也不會 眼見不一定為真 ----

quote from delphi help: procedure TForm1.FormCreate(Sender: TObject); begin Button1.Caption := 'Ignore Messages'; Button2.Caption := 'Process Messages'; end; procedure TForm1.Button1Click(Sender: TObject); var I, J, X, Y: Word; begin I := 0; J := 0; while I < 64000 do begin Randomize; while J < 64000 do begin Y := Random(J); Inc(J); end; X := Random(I); Inc(I); end; Canvas.TextOut(10, 10, 'The Button1Click handler is finished'); end; procedure TForm1.Button2Click(Sender: TObject); var I, J, X, Y: Word; begin I := 0; J := 0; while I < 64000 do begin Randomize; while J < 64000 do begin Y := Random(J); Inc(J); Application.ProcessMessages; end; X := Random(I); Inc(I); end; Canvas.TextOut(10, 10, 'The Button2Click handler is finished'); from this example i cant see any usefulness of application.processmesssages. would someone can explain in more detail to me? thanx

引言:

quote from delphi help:
procedure TForm1.FormCreate(Sender: TObject);
begin
  Button1.Caption := 'Ignore Messages';
  Button2.Caption := 'Process Messages';
end;    procedure TForm1.Button1Click(Sender: TObject);
var
  I, J, X, Y: Word;
begin
  I := 0;
  J := 0;
  while I < 64000 do
  begin
    Randomize;
    while J < 64000 do
    begin
      Y := Random(J);
      Inc(J);
    end;
    X := Random(I);
    Inc(I);
  end;
  Canvas.TextOut(10, 10, 'The Button1Click handler is finished');    end;    procedure TForm1.Button2Click(Sender: TObject);
var
  I, J, X, Y: Word;
begin
  I := 0;
  J := 0;
  while I < 64000 do
  begin
    Randomize;
    while J < 64000 do
    begin
      Y := Random(J);
      Inc(J);
      Application.ProcessMessages
    end;
    X := Random(I);
    Inc(I);
  end;
  Canvas.TextOut(10, 10, 'The Button2Click handler is finished');    from this example i cant see any usefulness of application.processmesssages. would someone can explain in more detail to me? thanx    Application.ProcessMessages;//读取消息队列 ,程序会在每个循环中查询是否有新的消息，并进行处理，避免程序在处理循环的时候出现死锁。
如上面的例子，您可以多加一个button在form中，如下：
procedure TForm1.Button3Click(Sender: TObject);
begin
  showmessage('can respond ');
end;
其实帮助上已经说得很清楚，即加上Application.ProcessMessages;在执行button2的循环语句时，同时也会响应botton3的onclick事件，而不加上Application.ProcessMessages则必须先执行完循环语句后才能响应其他事件，不能避免程序在处理循环的时候出现死锁，您可以在上面的语句中将循环的次数调大点，就很明显的可以看出效果来，试试看     >
 

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