Delphi：检测何时创建了新表单 [英] Delphi: Detect when a new form has been created

问题描述

我想检测何时创建了新表单。

I'd like to detect when a new form has been created.

现在，我使用 Screen.ActiveFormChange 事件并检查 Screen.CustomForms 中是否有新表单，但之后会触发 ActiveFormChange 表单的OnShow 事件。

Now I use the Screen.ActiveFormChange event and check for new forms in Screen.CustomForms but ActiveFormChange is fired after the OnShow event of the form.

我想在 OnShow 被解雇了。是否可以在不修改 Vcl.Forms 单元的情况下执行此操作？

I'd like to detect the form even before OnShow was fired. Is there any way to do this without modifying the Vcl.Forms unit?

我想检测所有表单（也包括Delphi模态消息等），因此不可能从自定义类继承所有表单（如果我错了，请纠正我）。

I'd like to detect all forms (also Delphi modal messages etc.) therefore inheriting all forms from a custom class is not possible (correct me if I am wrong).

或者，是否有可能是否检测到某个新组件已添加到某些 TComponent.FComponents 列表中？

Alternatively, is it possible to detect that a new component was added to some TComponent.FComponents list?

推荐答案

您可以使用 SetWindowsHookEx 函数安装 WH_CBT 挂钩，则必须实现 CBTProc回调函数，并最终拦截其中一个可能的代码钩子的值。在这种情况下，您可以尝试使用 HCBT_ACTIVATE 或 HCBT_CREATEWND 。

You can use the SetWindowsHookEx function to install a WH_CBT Hook, then you must implement a CBTProc callback function and finally intercept one of the possible code values for this hook. in this case you can try with HCBT_ACTIVATE or HCBT_CREATEWND.

检查此示例的 HCBT_ACTIVATE 代码。

var
 hhk: HHOOK;

function CBT_FUNC(nCode: Integer; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;
const
  ClassNameBufferSize = 1024;
var
 hWindow: HWND;
 RetVal : Integer;
 ClassNameBuffer: Array[0..ClassNameBufferSize-1] of Char;
begin
   Result := CallNextHookEx(hhk, nCode, wParam, lParam);
   if nCode<0 then exit;
   case nCode of
     HCBT_ACTIVATE:
     begin
       hWindow := HWND(wParam);
       if (hWindow>0) then
       begin
          RetVal := GetClassName(wParam, ClassNameBuffer, SizeOf(ClassNameBuffer));
          if RetVal>0 then
          begin
            //do something  
            OutputDebugString(ClassNameBuffer);                     
          end;
       end;
     end;
   end;

end;

Procedure InitHook();
var
  dwThreadID : DWORD;
begin
  dwThreadID := GetCurrentThreadId;
  hhk := SetWindowsHookEx(WH_CBT, @CBT_FUNC, hInstance, dwThreadID);
  if hhk=0 then RaiseLastOSError;
end;

Procedure KillHook();
begin
  if (hhk <> 0) then
    UnhookWindowsHookEx(hhk);
end;

initialization
  InitHook();

finalization
  KillHook();

end.

注意：如果使用 HCBT_CREATEWND 代码，您将
拦截系统创建的任何窗口，而不仅仅是表单。

Note : if you uses the HCBT_CREATEWND code instead you will intercept any window created by the system not just "forms".

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