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  1. #1
    dkas is offline Member
    Join Date
    Dec 2010
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    Default Using jna for SendMessage Windows call

    I am trying to use jna for making a win32 API call. I need to SendMessage to a window.

    I have a long handle and I am trying to pass it as follows but SendMessage is not returning the correct value. Can someone throw some light on what is wrong with the way I am passing the handle ?

    System.out.println("Process ID: " + activeWindow1.getPid());

    long handle1 = activeWindow1.getHandle(); // This prints 263948
    NativeLong nl = new NativeLong(handle1);

    User32 lib = User32.INSTANCE;
    NativeLongByReference nlbr = new NativeLongByReference(nl);

    long ret1 = lib.SendMessageA(new LongByReference(handle1).getPointer().getPointer(0 ), 32771, 0, 0);

    System.out.println("Return value=" + ret1); // This returns 8975925931411506151, expected is 999
    long ret2 = lib.SendMessageA(nlbr.getPointer().getPointer(0), 32771, 0, 0);
    System.out.println("Return value=" + ret2); //This call also returns 8975925931411506151, expected is 999


    // This is the standard, stable way of mapping, which supports extensive
    // customization and mapping of Java to native types.
    public interface User32 extends com.sun.jna.platform.win32.User32 {
    User32 INSTANCE = (User32)
    long SendMessageA(Pointer hWnd,int msg,int num1,int num2);
    long SendMessageA(PointerType hWnd,int msg,int num1,int num2);

  2. #2
    toadaly is offline Senior Member
    Join Date
    Jan 2009
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    cross post

    It's bad form to post the same question on multiple forums, but I understand why you are doing it since you are not getting any help. From a cursory look at the User32.SendMessageA, it is supposed to return a handle. Handles can change from run to run, so I'm not sure why you expect it to be 999.

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