Help me get thumbnails from Android's running apps?

gistfile1.java

/*
 *  This code doesn't work, I'm hoping for some help.
 *
 *  I'm trying to use reflection to dig into Android's @hide classes that store screenshots
 *  of the currently running apps.
 *
 *  The code compiles and runs perfectly, but mThumbnailReceiver is never called back with
 *  the bitmaps.
 *
 *  I've never done Android development before (I'm an iOS dev) but I'd love to get this
 *  (or any other thumbnail code) to work for a personal project I'm starting. Any and all
 *  help is welcome.
 *
 *  I've spent hours on Google looking for other people who've done the same thing, no one
 *  has without modifying their ROM.
 *
 * Google's working source code for reference
 *  The recent tasks app calling the thumbnails: http://androidxref.com/4.0.4/xref/frameworks/ex/carousel/test/src/com/android/carouseltest/TaskSwitcherActivity.java#245
 *
 *  The callback it uses: http://androidxref.com/4.0.4/xref/frameworks/ex/carousel/test/src/com/android/carouseltest/TaskSwitcherActivity.java#167
 * 
 *  The IThumbnailReceiver class: http://code.google.com/p/coffee/source/browse/trunk/froyo/android/android/app/IThumbnailReceiver.java?r=392
 */

        try
        {
            ActivityManager am = (ActivityManager)this.getSystemService(ACTIVITY_SERVICE);
            
            Class IThumbnailReceiver = Class.forName("android.app.IThumbnailReceiver");
            Class StubClass = Class.forName("android.app.IThumbnailReceiver$Stub");
            java.lang.reflect.Constructor stub = StubClass.getConstructor();
            
            Object mThumbnailReceiver = java.lang.reflect.Proxy.newProxyInstance(IThumbnailReceiver.getClassLoader(), new java.lang.Class[]{IThumbnailReceiver}, new java.lang.reflect.InvocationHandler()
            {
                @Override
                public Object invoke(Object proxy, java.lang.reflect.Method method, Object[] args) throws java.lang.Throwable
                {
                    Log.d(LOG_TAG, "invoke method: " + method.getName());
                    
                    String method_name = method.getName();
                    Class<?>[] classes = method.getParameterTypes();

                    if(method_name.equals("finished"))
                    {
                    }
                    else if(method_name.equals("newThumbnail")) 
                    {
                        Bitmap bitmap = (Bitmap)args[1];
                        int w = bitmap.getWidth();
                        int h = bitmap.getHeight();

                        Log.d(LOG_TAG, "New thumbnail for id=" + args[0] + ", dimensions=" + w + "x" + h + " description '" + args[2] + "'");
                    }
                    else if(method_name.equals("asBinder"))
                    {
                    }
                    return null;
                }
            });
          
            Class c = Class.forName("android.app.ActivityManager");
            
            Class[] args = new Class[3];
            args[0] = Integer.TYPE;
            args[1] = Integer.TYPE;
            args[2] = Class.forName("android.app.IThumbnailReceiver");
            java.lang.reflect.Method method = c.getMethod("getRunningTasks", args);
            
            Object[] input = {new Integer(5), new Integer(0), mThumbnailReceiver};
            List<ActivityManager.RunningTaskInfo> lru = (List<ActivityManager.RunningTaskInfo>)method.invoke(am, input);
            
            for(ActivityManager.RunningTaskInfo rti : lru) 
            {
                Log.d(LOG_TAG, "LRU: " + rti.topActivity.getClassName());
                
                Bitmap b = rti.thumbnail;
                if(b != null)
                {
                    Log.d(LOG_TAG, "	Bitmap found: " + b);
                } 
                else 
                {
                    Log.d(LOG_TAG, "	Bitmap is null");
                }
            }
        }
        catch(Exception e)
        {
            Log.d(LOG_TAG, "Exception" + e);
        }

Did you ever get this working? I've wanted to do something similar, but couldn't quite figure out how to. From what I know you need use the same API that SystemUI uses, which requires the READ_FRAME_BUFFER permission and that is only available to system apps. But if you've found a way around this I'd love to know.

You need add GET_TASKS permission in your AndroidManifest.xml
and Line 76: Bitmap b = rti.thumbnail; will always be Null. See: http://developer.android.com/reference/android/app/ActivityManager.RunningTaskInfo.html#thumbnail

Did you solved this issue? I tried this code but i got the null on all apps list. If you solved this issue, can you explain the solution of this issue?