forms - 在 Delphi 中线程打开表单

Question

我想从线程创建新的表单实例(并显示它们)。但它似乎卡住了我的应用程序和我的线程(我的线程变成了非同步线程，并且它卡住了我的应用程序)。

像这样(但它并没有达到我想要的效果)

procedure a.Execute;
var frForm:TForm;
    B:TCriticalSection;
begin
   b:=TCriticalSection.Create;
   while 1=1 do
   begin
     b.Enter;

        frForm:=TForm.Create(Application);
        frForm.Show;
     b.Leave;
     sleep(500); //this sleep with sleep my entire application and not only the thread.
      //sleep(1000);
   end;
end;

我不想使用Classes.TThread.Synchronize方法

Answer 1

TThread.Synchronize() 是最简单的解决方案:

procedure a.Execute;
begin
  while not Terminated do
  begin
    Synchronize(CreateAndShowForm);
    Sleep(500);
  end;
end;

procedure a.CreateAndShowForm;
var
  frForm:TForm;
begin
  frForm:=TForm.Create(Application);
  frForm.Show;
end;

如果您使用的是现代版本的 Delphi，并且不需要等待 TForm 创建完成才让线程继续，您可以使用 TThread.Queue() 相反:

procedure a.Execute;
begin
  while not Terminated do
  begin
    Queue(CreateAndShowForm);
    Sleep(500);
  end;
end;

更新:如果您想使用 PostMessage()，最安全的选择是将消息发布到 TApplication 窗口或通过AllocateHWnd()创建的专用窗口，例如:

const
  WM_CREATE_SHOW_FORM = WM_USER + 1;

procedure TMainForm.FormCreate(Sender: TObject);
begin
  Application.OnMessage := AppMessage;
end;

procedure TMainForm.AppMessage(var Msg: TMsg; var Handled: Boolean);
var
  frForm:TForm;
begin
  if Msg.message = WM_CREATE_SHOW_FORM then
  begin
    Handled := True;
    frForm := TForm.Create(Application);
    frForm.Show;
  end;
end;

procedure a.Execute;
begin
  while not Terminated do
  begin
    PostMessage(Application.Handle, WM_CREATE_SHOW_FORM, 0, 0);
    Sleep(500);
  end;
end;

.

const
  WM_CREATE_SHOW_FORM = WM_USER + 1;

var
  ThreadWnd: HWND = 0;

procedure TMainForm.FormCreate(Sender: TObject);
begin
  ThreadWnd := AllocateHWnd(ThreadWndProc);
end;

procedure TMainForm.FormDestroy(Sender: TObject);
begin
  DeallocateHwnd(ThreadWnd);
  ThreadWnd := 0;
end;

procedure TMainForm.ThreadWndProc(var Message: TMessage);
var
  frForm:TForm;
begin
  if Message.Msg = WM_CREATE_SHOW_FORM then
  begin
    frForm := TForm.Create(Application);
    frForm.Show;
  end else
    Message.Result := DefWindowProc(ThreadWnd, Message.Msg, Message.WParam, Message.LParam);
end;

procedure a.Execute;
begin
  while not Terminated do
  begin
    PostMessage(ThreadWnd, WM_CREATE_SHOW_FORM, 0, 0);
    Sleep(500);
  end;
end;