About "Always on Top" windows

Question

Hi all,
My application needs an always on top window and I used a dll written
by Mitch Goldstein. It works perfectly on jvm 1.3.1, but when I try it
on jvm1.4.1 which is more popular today than 1.3.1, it just doesn't
work, without any exceptions.
Can anybody give some hints? Thanks a lot.
The "Always on top" package written by Mitch Goldstein with examples
can be downloaded from the following address:
http://www.esus.com/javaindex/j2se/jdk1.2/javaxswing/toplevelcontainers/jframe/jframealwaysontop.html

Answer 1

For JRE 1.3 and above, the following code addresses the issue of having two windows with the same title. The function takes a Frame as a parameter, gets the HWND using the AWT Native Interface, and then calls SetWindowPos. Agreed, this code is far more complicated than smg123's solution, but if there's a chance of two windows having the same title, it's probably better to use this:JNIEXPORT void JNICALL Java_JSystem_setWindowAlwaysOnTop__Ljava_awt_Frame_2Z (JNIEnv *env, jclass cls, jobject frame, jboolean flag)
     typedef jboolean (JNICALL* PJAWT_GetAWT) (JNIEnv*, JAWT*); // Function pointer
     JAWT jawt;
     JAWT_DrawingSurface* jds;
     JAWT_DrawingSurfaceInfo* jdsi;
     JAWT_Win32DrawingSurfaceInfo* jdsi_win;
     HANDLE hAWT;
     HWND hwnd;
     jboolean result;
     PJAWT_GetAWT JAWT_GetAWT;
     LPTSTR buf;
     jclass sys;
     jmethodID home;
     jstring ret;
        // This section of code is needed in order to find jawt.dll
     sys = (*env)->FindClass (env, "java/lang/System");
     home = (*env)->GetStaticMethodID (env, sys, "getProperty", "(Ljava/lang/String;)Ljava/lang/String;");
     ret = (jstring)(*env)->CallStaticObjectMethod(env, sys, home, (*env)->NewStringUTF (env, "java.home"));
     buf = (LPTSTR)(*env)->GetStringUTFChars (env, ret, NULL);
     strcat (buf, "\\bin\\jawt.dll");
     hAWT = LoadLibrary ((LPCTSTR)buf);
     if (!hAWT) return;
     JAWT_GetAWT = (PJAWT_GetAWT)GetProcAddress(hAWT, "_JAWT_GetAWT@8");
     jawt.version = JAWT_VERSION_1_3;
     result = JAWT_GetAWT (env, &jawt);
     jds = jawt.GetDrawingSurface (env, frame);
     jds->Lock(jds);
     jdsi = jds->GetDrawingSurfaceInfo (jds);
     jdsi_win = (JAWT_Win32DrawingSurfaceInfo *)jdsi->platformInfo;
     hwnd = jdsi_win->hwnd;
     SetWindowPos (hwnd, flag ? HWND_TOPMOST : HWND_NOTOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
     jds->FreeDrawingSurfaceInfo (jdsi);
     jds->Unlock(jds);
     jawt.FreeDrawingSurface (jds);
     (*env)->ReleaseStringUTFChars (env, ret, buf);
}Note that you must include jawt_md.h as that's where all the types such as JAWT are declared. You can link statically with jawt.lib, but as it is dangerous to assume the JRE version on the user's system, it's probably a better idea to link dynamically and handle any errors that occur.
Hope that helps.
Cheers