Re: Terminating external application

Posted by webmaster Guido on January 14, 2009

In Reply to Terminating external application posted by Thomas L on January 14, 2009

: I have been successfully using ShellExecute to launch a separate exe in my delphi code (a movie player), but don't have as good a solution for terminating the player.

Closing (stopping) an application can be done by closing its main window. That's done by sending a close-message to that window:
PostMessage(WindowHandle, WM_CLOSE, 0, 0)

One way to get WindowHandle is with:
FindWindow(PointerToClassName, PointerToWindowTitle)

If you know the text in the titlebar of the application that you want to close, you can try the following Delphi code example:

procedure TForm1.CloseAppTitle(WinTitle: string);
var
  H: HWND;
begin
  H := FindWindow(nil, PChar(WinTitle));
  if H <> 0 then 
    PostMessage(H, WM_CLOSE, 0, 0);
end;

For example, if you want to stop the program 'Calculator', you would write:
CloseAppTitle('Calculator')

If you don't know the title of the window, maybe you know the window class name. Then try this code:

procedure TForm1.CloseAppClassName(CName: string);
var
  H: HWND;
begin
  H := FindWindow(PChar(CName), nil);
  if H <> 0 then 
    PostMessage(H, WM_CLOSE, 0, 0);
end;

For example, for closing 'Internet Explorer', of which we know that the class name of its main window is 'IEFrame':
CloseAppClassName('IEFrame');

There are utilities to get the class names, such as WinDowse, WinSpector Spy, and others.
Use of WinDowse:
   - start this utility and select the tab "Class";
   - next, move your mouse cursor over the title bar of running applications and watch WinDowse :)

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