Programmatically taking screenshot of the top running activity

Question

I am trying to take screenshot of the top running activity view programmatically using the following code and then I'll share the bitmap to a socket server program every interval. After a long research I got this code working. But the issue is, This code is not taking top running activity (whichever the top running activity in my app), instead it is taking screenshot of the particular activity only where this code is written. It is not taking screenshot of any activity which is running on the foreground. Could someone please advise, what may be wrong here?

    private Runnable mUpdate = new Runnable() {

        public void run() {

            //ActivityManager mActivityManager = (ActivityManager) getSystemService(Activity.ACTIVITY_SERVICE);
            //List<ActivityManager.RunningTaskInfo> task = mActivityManager.getRunningTasks(1); 
            //ComponentName componentInfo = task.get(0).topActivity;
            //mActivityManager.getRunningTasks(1).get(0).topActivity.
            //View view = getWindow().getDecorView().findViewById(android.R.id.content);
            //getWindow().findViewById(android.R.id.content)


            View view = getWindow().getDecorView().findViewById(android.R.id.content);
            context = getApplicationContext(); 

            try {
               // HERE IS THE SCREENSHOT TAKEN PROGRAMMATICALLY
                bitmap = loadBitmapFromView(context,view);

                //bitmap = takeScreenshot();
                output = ((GlobalClass) RandomIDActivity.this.getApplication()).socket.getOutputStream();
                Log.d("ClientActivity", "C: image writing.");
                ByteArrayOutputStream stream = new ByteArrayOutputStream();
                bitmap.compress(CompressFormat.JPEG, 70, stream);
                byte[] imgbyte = stream.toByteArray();

                String endStr = "END";
                byte[] endByte = endStr.getBytes();

                byte[] finalByteToSend = new byte[imgbyte.length + endByte.length];
                System.arraycopy(imgbyte, 0, finalByteToSend, 0, imgbyte.length);
                System.arraycopy(endByte, 0, finalByteToSend, imgbyte.length, endByte.length);

                output.write(finalByteToSend,0,finalByteToSend.length);
                output.flush();
                imgbyte = null;
                endByte = null;
                finalByteToSend = null;

                }
                catch (Exception ex) {
                    ex.printStackTrace();
                } 

            shareHandler.postDelayed(this, 5000);
        }

        };

Extracting as bitmap here,

public static Bitmap loadBitmapFromView(Context context, View v) {

        DisplayMetrics dm = context.getResources().getDisplayMetrics();

        v.measure(MeasureSpec.makeMeasureSpec(dm.widthPixels, MeasureSpec.EXACTLY),
                MeasureSpec.makeMeasureSpec(dm.heightPixels, MeasureSpec.EXACTLY));

        v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());

        Bitmap returnedBitmap = Bitmap.createBitmap(v.getMeasuredWidth(),
                v.getMeasuredHeight(), Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(returnedBitmap);

        v.draw(canvas);
        return returnedBitmap;
    }

UPDATE CODE:

ActivityManager mActivityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);

List<ActivityManager.RunningTaskInfo> task = mActivityManager.getRunningTasks(1); 

String currActivityString = task.get(0).topActivity.getClassName();

try {
            Log.d("currActivityString: ", "currActivityString: " + currActivityString);
            Log.d("Test 1111" , "Test 1111");
            myCurrClass = Class.forName(currActivityString);
            Log.d("Test 2222" , "Test 2222");
            } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            }

            try {
            Log.d("Test 3333" , "Test 3333");
            activityObj = (Activity) myCurrClass.newInstance();
            Log.d("Test 4444" , "Test 4444");
            } catch (InstantiationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            }
*// CRASHING IN THIS LINE as Fatal Exception: NullPointerException*
View view = activityObj.getWindow().getDecorView().getRootView();

bitmap = loadBitmapFromView(activityObj,view);

Answer 1

getWindow() is a method of Activity. Each activity has a different Window instance.

To find the top (foreground) activity, see: Android: How can I get the current foreground activity (from a service)?

Answer 2

There is a very good way to go about this. Create a class names CommonUtils and create a method there which will be used to take screen shots and send it to stream like this:

CommonUtils.java

public static byte[] takeScreenShot(Activity context){
    View view = context.getWindow().getDecorView().getRootView();
    view.setDrawingCacheEnabled(true);
    Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache());
    view.setDrawingCacheEnabled(false);
    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    bitmap.compress(CompressFormat.JPEG, 70, stream);
    return stream.toByteArray();
    // now that you have the byte array you can send it when ever you want.
}

now all you have to do is call this mehod inside any of your activity like this:

CommonUtils.takeScreenShot(MyCurrentActivity.this);

[Note]: you can either send it right away inside the same method or anywhere else by using the byte[]

[EDIT]: As you have mentioned in the comments that you are able to get the top running Activity. Store its instance and make the following changes in your Runnable:

Lets say you have stored the top activity's instance as topActivity

Activity topActivity = //your top activity;
View view = topActivity.getWindow().getDecorView().getRootView();

and you need to do this very minor change in your loadBitmapFromView() method:

public static Bitmap loadBitmapFromView(Activity context, View v) {

you dont need to change the rest in this method.

and call this like this inside your Runnable:

bitmap = loadBitmapFromView(topActivity,view);

Hope it helps :)

Answer 3

Problem may not with your screen capture function(which I didn't check).

when your code execute it became top running activity and take screenshot of it. best solution i think make your activity invisible and take screenshot then it take screenshot of toprunning activity before execute your activity.

to make your activity invisible apply this style and check

style.xml

<?xml version="1.0" encoding="UTF-8"?>
<resources>
    <style name="Invisible" parent="@android:style/Theme">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowIsFloating">true</item>
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowContentOverlay">@null</item>
        <item name="android:backgroundDimEnabled">false</item>
    </style>
</resources>

and in AndroidManifet apply this to your activity

<activity
    android:name=".MyActivity"
    android:label="@string/app_name"
    android:theme="@style/Invisible"
>

to make activity visible after capture screen, you can setTheam to default

check this also How do I create a transparent Activity on Android?