利用RegisterWindowMessage在不同程序窗体间传递消息

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 Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
UserMessage : UINT;
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
sendmessage(HWND_BROADCAST,UserMessage ,handle,0);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
UserMessage  :=   RegisterWindowMessage('WM_SAMPLE');
end;

end.

unit Unit2;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls;

type
TForm2 = class(TForm)
Image1: TImage;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
UserMessage  :   UINT;
procedure   GetImage(Form1Window   :   HWND);
public
{ Public declarations }
protected
procedure   WndProc(var   Message:   TMessage);   override;
end;

var
Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.FormCreate(Sender: TObject);
begin
UserMessage   :=   RegisterWindowMessage('WM_SAMPLE');
end;

procedure   TForm2.WndProc(var   Message:   TMessage);
begin
if   Message.Msg   =   UserMessage   then
GetImage(Message.WParam)
else   inherited;
end;

procedure   TForm2.GetImage(Form1Window   :   HWND);
var
Form1DC:   HDc;
Form1Rect:   TRect;
begin
image1.Picture   :=   nil;
Form1DC   :=   GetWindowDC(Form1Window);
GetWindowRect(Form1Window,Form1Rect);
image1.Width   :=   Form1Rect.Right-Form1Rect.Left;
image1.Height   :=   Form1Rect.Bottom   -   Form1Rect.Top;
BitBlt(Image1.Canvas.Handle,0,0,image1.Width,
image1.Height,
Form1DC,   0,
0,   SRCCOPY);
Image1.Refresh;
ReleaseDC(Form1Window,   Form1DC);
SetForegroundWindow(handle);
beep;

end;

end.