执行过程时，Gif图像的动画不起作用

问题描述

我有一个Delphi项目，该项目由两种形式组成，即 MainForm 和 DialogForm 。当我单击 Button1 时，应出现 DialogForm 并停留在顶部，直到过程完成（该过程需要几秒钟才能完成）。

对话框表单包括一个图像组件。当我单击 Button1 以显示 DialogForm 时，会出现Gif图像，但没有动画。仅当过程开始时才会发生这种情况（动画不执行过程）。这是什么原因，以及如何保持动画直到关闭 DialogForm ？

？

procedure TMainForm.Button1Click(Sender: TObject);
var
  gif: TGIFImage;
begin
  Enabled:=false;
  try
        DialogForm.Show;
        DialogForm.Refresh;

        // The process is:
         ...
        ipcAES1.Encrypt;//where ipcAES is part of the IPWorks Encrypt library
        RichEdit1.Text:=ipcAES1.OutputMessage;
    finally
        Enabled:= true;
        DialogForm.Close;
    end;

end;
//--------------------------------------- 
procedure TDialogForm.FormShow(Sender: TObject);
var
  gif: TGIFImage;
begin
  gif := TGIFImage.Create;
  gif.LoadFromFile('D:\preview.gif');
  gif.Animate := True;
    image1.Parent := Self;
    image1.Left := 0;
    image1.Top := 0;
    image1.width := 800;
    image1.height := 800;
    image1.Picture.Assign(gif);
    gif.Animate := True;
    gif.Free;  
end;

解决方法

正如该线程中的许多人所说，由于处理是在主线程中完成的，因此在此过程中不会更新UI。

要确保在进程运行时更新UI，请让一个单独的线程进行处理：

procedure TForm1.Button1Click(Sender: TObject);
var
  aProcessingThread: TThread;
begin
  // First read all data needed by the process from UI controls (or other non-threadsafe parts)
  <data> := ...;

  // Then create a new (anonymous) thread with the code you need to run your process
  aProcessingThread := TThread.CreateAnonymousThread(
    procedure
    begin
      // create the objects you need to do the processing
      ipcAES1 := Txxx.Create;
      try
        // Set the data
        ipcAES1.<data> := <data>;

        // Execute the proces:
        // ...
        ipcAES1.Encrypt;

      finally
        // When the process is done,use 'Synchronize' to interact with the UI
        // again,so you can add the processed data to the RichtEdit and so on...
        TThread.Synchronize(nil,procedure
          begin
            // Now you can interact again with the UI
            RichEdit1.Text := ipcAES1.OutputMessage;
            Enabled:= true;
            DialogForm.Close;
          end);
        ipcAES1.Free;
      end;
    end);

  // The thread is now created,but not started/running,so you can now show
  // the dialog and then start the thread,at which point the ButtonClick event
  // exists,but the progress dialog is shown and the thread is running.
  Enabled := False;
  DialogForm.Show;
  aProcessingThread.Start;
end;

当然，这仅是一个基本示例，说明如何使用（匿名）线程在后台进行一些处理。 请注意，您需要处理线程内的异常（try / except）。

有关TGifImage加载的小技巧：只要在uses子句中包含Picture.LoadfromFile，您就可以调用Vcl.Imaging.GIFImg来加载gif。

procedure TForm1.FormShow(Sender: TObject);
begin
  image1.Picture.LoadFromFile('D:\preview.gif');

  image1.Parent := Self;
  image1.Left := 0;
  image1.Top := 0;
  image1.width := Image1.Picture.Width;
  image1.height := Image1.Picture.Height;

  (image1.Picture.Graphic as TGIFImage).Animate := True;
end;