哪个是初始化代码的最佳位置？ [英] Which is the best place to initialize code?

问题描述

可能重复：

以编程方式启动屏幕

在数据库连接（可能需要很长时间）运行时显示启动画面

哪个是初始化代码（例如加载INI文件）的最佳位置？我想首先在屏幕上显示该表单，以便用户知道该应用程序正在加载，然后才要调用冗长的函数，例如LoadIniFile或IsConnectedToInternet（最后一个确实很慢）。

Which is the best place to initialize code such as loading INI file? I want first to show the form on screen so the user know that the app is loading and ONLY after that I want to call lengthy functions such as LoadIniFile or IsConnectedToInternet (the last one is REALLY slow).

OnCreate不好，因为该表单尚未准备好，它不会显示在屏幕上。

The OnCreate is not good because the form is not yet ready and it will not show up on screen.

我这样做是DPR，但不是始终工作：

I do this I DPR but not working always:

program Test;
begin
  Application.Initialize;
  Application.Title := 'Test app';
  Application.CreateForm(TfrmTest, frmTest);
  frmTest.Show;               <---------------------- won't show
  LateInitialize;
  Application.Run;
end.

在执行LateInitialize（4-5秒）之前，不会显示该表单。

The form will not show until LateInitialize (4-5 seconds) is executed.

procedure LateInitialize;
begin
 CursorBussy;
 TRY
  // all this won't work also. the form won't show
  frmTest.Visible:= TRUE;
  Application.ProcessMessages; 
  frmTest.Show;
  Application.ProcessMessages;
  frmTest.BringToFront;
  frmTest.Update;
  Application.ProcessMessages;

  DoSomethingLengthy;     {4-5 seconds}
 FINALLY
  CursorNotBussy;
 END;
end;     <--------- Now the form shows.

是的，frmTest是我唯一的形式（主要形式）。

And yes, frmTest it is my only form (the main form).

推荐答案

调用 frmTest.Show 后，可以调用 frmTest.Update 使其呈现在屏幕上，然后调用 LateInitialize 。但是，在调用 Application.Run 之前，主消息循环将不会运行，因此该表单在此之前将无法执行其他任何操作。

After calling frmTest.Show, you can call frmTest.Update to let it render onscreen, before then calling LateInitialize. But until Application.Run is called, the main message loop will not be running, so the form will not be able to do anything else until then.

另一种选择是使用表单的 OnShow 事件，通过 PostMessage将自定义窗口消息发布回表单。 ），然后在以后收到该消息时，调用 LateInitialize 的形式。这将允许表单正常处理绘画消息，直到调用 LateInitialize 。

Another option is to use the form's OnShow event to post a custom window message back to the form via PostMessage(), then have the form call LateInitialize when it receives that message at a later time. That will allow the form to process painting messages normally until LateInitialize is called.

任何阻止主线程实际上应该将超过几毫秒/秒的时间移到单独的工作线程中（尤其是 IsConnectedToInternet 之类的东西）。主线程应用于运行UI。

Anything that blocks the main thread for more than a few milliseconds/seconds really should be moved into a separate worker thread instead (especially things like IsConnectedToInternet). The main thread should be used for running the UI.

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