对发给Application.Handle消息的三次执行(拦截)消息的过程
unit Main; interface uses SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type TMainForm = class(TForm) SendBtn: TButton; PostBtn: TButton; procedure SendBtnClick(Sender: TObject); procedure PostBtnClick(Sender: TObject); procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); private OldWndProc: Pointer; WndProcPtr: Pointer; procedure WndMethod(var Msg: TMessage); procedure HandleAppMessage(var Msg: TMsg; var Handled: Boolean); end; var MainForm: TMainForm; implementation {$R *.DFM} uses ScWndPrc; procedure TMainForm.SendBtnClick(Sender: TObject); begin SendMessage(Application.Handle, WM_USER, 0, 0); end; procedure TMainForm.PostBtnClick(Sender: TObject); begin PostMessage(Application.Handle, WM_USER, 0, 0); end; procedure TMainForm.HandleAppMessage(var Msg: TMsg; var Handled: Boolean); begin if Msg.Message = WM_USER then ShowMessage(Format('Message seen by OnMessage! Value is: $%x', [Msg.Message])); end; procedure TMainForm.WndMethod(var Msg: TMessage); begin if Msg.Msg = WM_USER then // 第二处处理(新的过程函数) ShowMessage(Format('Message seen by WndMethod! Value is: $%x', [Msg.Msg])); with Msg do Result := CallWindowProc(OldWndProc, Application.Handle, Msg, wParam, lParam); // 第三处处理(旧的过程函数) end; procedure TMainForm.FormCreate(Sender: TObject); begin Application.OnMessage := HandleAppMessage; // 第一处处理(先过OnMessage这关) WndProcPtr := MakeObjectInstance(WndMethod); // make window proc { Set window procedure of application window. } OldWndProc := Pointer(SetWindowLong(Application.Handle, GWL_WNDPROC, Integer(WndProcPtr))); end; procedure TMainForm.FormDestroy(Sender: TObject); begin { Restore old window procedure for Application window } SetWindowLong(Application.Handle, GWL_WNDPROC, Longint(OldWndProc)); { Free our user-created window procedure } FreeObjectInstance(WndProcPtr); end; end. unit Scwndprc; interface uses Forms, Messages; implementation uses Windows, SysUtils, Dialogs; var WProc: Pointer; function NewWndProc(Handle: hWnd; Msg, wParam, lParam: Longint): Longint; stdcall; { This is a Win32 API-level window procedure. It handles the messages } { received by the Application window. } begin if Msg = WM_USER then { If it's our user-defined message, then alert the user. } ShowMessage(Format('Message seen by WndProc! Value is: $%x', [Msg])); { Pass message on to old window procedure } Result := CallWindowProc(WProc, Handle, Msg, wParam, lParam); end; initialization { Set window procedure of Application window. } WProc := Pointer(SetWindowLong(Application.Handle, gwl_WndProc, Integer(@NewWndProc))); end.
对发给Application.Handle消息的总结:
1. 先过Application.OnMessage这关
2. 过新的过程函数这关
3. 还可继续传递给旧的过程函数
其中SendMessage发送到消息不经过消息泵,因此直接调用过程函数(先执行新的过程函数,再继续传递给旧的)