子类化——谁可以给我详细的讲解啊，看书看不懂。。。。。。(100分)

长发 · 2004-04-19

unit Unit1; interface uses   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,   Dialogs, StdCtrls; type   TForm1 = class(TForm)     Button1: TButton;     Button2: TButton;     procedure FormCreate(Sender: TObject);     procedure FormDestroy(Sender: TObject);     procedure Button1Click(Sender: TObject);     procedure Button2Click(Sender: TObject);   private     OldWndProc : Pointer;     WndProcPtr : Pointer;     Procedure WndMethod(var Msg : TMessage);     Procedure HandleAppMessage(var Msg : TMsg;var Handled : Boolean);   public   end; var   Form1: TForm1; implementation uses unit2; {$R *.dfm} { TForm1 } procedure TForm1.HandleAppMessage(var Msg: TMsg; var Handled: Boolean); begin   if Msg.message = DDGM_FOOMSG then     showmessage(Format('Message seen by OnMessage! value is: $%x',[Msg.message])); end; procedure TForm1.WndMethod(var Msg: TMessage); begin   if Msg.Msg = DDGM_FOOMSG then     showmessage(Format('Message seen by WndMethod! value is: $%x',[Msg.Msg]));   with Msg do     Result := callwindowProc(OldWndProc,Application.Handle,Msg,WParam,LParam); end; procedure TForm1.FormCreate(Sender: TObject); begin   Application.OnMessage := HandleAppMessage;//set OnMessage handler   WndProcPtr := MakeObjectInstance(WndMethod); //make window  Proc   OldWndProc := Pointer(SetWindowLong(Application.Handle,gwl_wndProc,Integer(WndProcPtr))); end; procedure TForm1.FormDestroy(Sender: TObject); begin   SetWindowLong(Application.Handle,GWL_WNDPROC,Longint(OldWndProc));   FreeObjectInstance(WndProcPtr); end; procedure TForm1.Button1Click(Sender: TObject); begin   SendMessage(Application.Handle,DDGM_FOOMSG,0,0); end; procedure TForm1.Button2Click(Sender: TObject); begin   PostMessage(Application.Handle,DDGM_FOOMSG,0,0); end; end. unit Unit2; interface uses Forms,Messages; const   DDGM_FOOMSG = WM_USER; implementation uses Windows,SysUtils,Dialogs; var   WProc : Pointer; Function NewWndProc(Handle : hWnd; Msg,WParam,LParam : LongInt):LongInt;stdcall; begin   if Msg = DDGM_FOOMSG then     showmessage(Format('Message seen by WndProc! value is: $%x',[Msg]));   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. 这是书上的例子但我老是不明白其中的每步的意思和他的原理那位GG可以给我详细讲解一下

林枫 · 2004-04-19

//************************************************************* //这段代码实现的就是拦载自定义消息的功能，Unit2.pas代码是自定义消息的消息号 //************************************************************* unit Unit1; interface uses   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,   Dialogs, StdCtrls; type   TForm1 = class(TForm)     Button1: TButton;     Button2: TButton;     procedure FormCreate(Sender: TObject);     procedure FormDestroy(Sender: TObject);     procedure Button1Click(Sender: TObject);     procedure Button2Click(Sender: TObject);   private     //定义指针变量(指向方法)     OldWndProc : Pointer;     WndProcPtr : Pointer;     //当接到DDGM_FOOMSG消息时，显示一个自定义对话框，否则调用WndMethod窗口消息处理过程     Procedure WndMethod(var Msg : TMessage);     //此方法用来取代Application.OnMessage方法，当接到DDGM_FOOMSG消息时，显示一个自定义对话框     Procedure HandleAppMessage(var Msg : TMsg;var Handled : Boolean);   public   end; var   Form1: TForm1; implementation uses unit2; {$R *.dfm} { TForm1 } procedure TForm1.HandleAppMessage(var Msg: TMsg; var Handled: Boolean); begin   if Msg.message = DDGM_FOOMSG then     showmessage(Format('Message seen by OnMessage! value is: $%x',[Msg.message])); end; procedure TForm1.WndMethod(var Msg: TMessage); begin   if Msg.Msg = DDGM_FOOMSG then     showmessage(Format('Message seen by WndMethod! value is: $%x',[Msg.Msg]));   with Msg do     Result := callwindowProc(OldWndProc, Application.Handle, Msg, WParam,LParam); end; procedure TForm1.FormCreate(Sender: TObject); begin   //设置OnMessage的句柄，当接到消息时，调用HandleAppMessage方法   Application.OnMessage := HandleAppMessage;   //将WndProcPtr这个指针变量指向WndMethod方法(自定义的)   WndProcPtr := MakeObjectInstance(WndMethod);   //SetWindowLong(Application.Handle,gwl_wndProc,Integer(WndProcPtr)用来改变窗口属性，返回窗口句柄   OldWndProc := Pointer(SetWindowLong(Application.Handle, gwl_wndProc, Integer(WndProcPtr))); end; procedure TForm1.FormDestroy(Sender: TObject); begin   SetWindowLong(Application.Handle, GWL_WNDPROC, Longint(OldWndProc));   //释放WndProcPtr指针变量占用的内存   FreeObjectInstance(WndProcPtr); end; procedure TForm1.Button1Click(Sender: TObject); begin   SendMessage(Application.Handle,DDGM_FOOMSG,0,0); end; procedure TForm1.Button2Click(Sender: TObject); begin   PostMessage(Application.Handle,DDGM_FOOMSG,0,0); end; end.

长发 · 2004-04-19

to 林枫,   SetWindowLong 这个函数是干什么用的啊？

QSmile · 2004-04-21

Delphi 里一般用不着自己子类化 这是在 C SDK /ASM SDK 中才用的。

lichdr · 2004-04-21

The SetWindowLong function changes an attribute of the specified window. The function also sets a 32-bit (long) value at the specified offset into the extra window memory of a window. If the function succeeds, the return value is the previous value of the specified 32-bit integer. If the function fails, the return value is zero. To get extended error information, call GetLastError. 就是設置窗口某個attributer的地址。 gwl_wndProc：表示SetWindowLong(Application.Handle, gwl_wndProc, Integer(WndProcPtr）設置這個程序的wndproc為自定的那個方法。 在FormCreate處要把舊的wndproc存起來（就是OldWndProc ） 在FormDestroy進還原（否則會出事的）。

子类化——谁可以给我详细的讲解啊，看书看不懂。。。。。。(100分)

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