在桌面中心定位表格时出现异常

Question

我的主窗体启动时 WindowState 为 wsMaximized，Position 为 poDefault。当我点击 maximize/minimize 切换按钮时，我希望将缩小的表格放置在桌面中心。所以在 OnResize 中我放置了以下内容：

if WindowState = wsMaximized then
    Position := poDefault
 else if WindowState = wsNormal then
    Position := poScreenCenter;

当我的程序启动时，我得到这个异常：'Cannot change visible in OnShow or OnHide'。

我应该怎么做才能使我的表单最大化或正常居中？

Answer 1

FormResize 方法在您的表单首次显示时发生。第一次创建或展示时一定要检查表格的当前状态，不要尝试调整表格大小

procedure TForm1.FormResize(Sender: TObject);
begin
    if not(fsVisible in Self.FormState) then
      Exit;

    if WindowState = wsMaximized then
      Position := poDefault
    else
      if WindowState = wsNormal then
        Position := poScreenCenter;
end;

在 http://docwiki.embarcadero.com/Libraries/en/Vcl.Forms.TFormState

阅读更多内容

以下 table 列出了可以包含在表单状态中的值：

Value Meaning

fsCreating -- The form's constructor is currently executing.

fsVisible -- The form's window is visible. This state is used to update the Visible property.

fsShowing -- The form's WindowState property is changing. This state is used to prevent WindowState changes from interfering with a transition that is in progress.

fsModal -- The form was created as a modal window.

fsActivated -- The form has received focus or the application became active but has not yet called the Activate method to generate an OnActivate event.

在桌面中心定位表格时出现异常

Exception while positioning form at desktop center

delphi

delphi-2009