Android: at what point is the activity completely loaded and presenting itself?

Question

I want quite simple thing - to know when is my activity completely loaded and presenting itself on the screen - that is when I want a piece of code to run. That piece of code starts by taking a screenshot and running some animations on it. I wrote that code in onResume() and everything is fine during normal start up, but when I rotate the device the screenshot is taken from the previous orientation, although all the display parameter dumps show that the orientation is already changed. It seems like the system re-creates, re-runs and re-draws my Activity still physically showing the previous state and then it runs the system rotation animation between 2 states and finally shows my Activity. This also implies that any android app starting any animation in onResume will lose the first X milliseconds of it because of the system rotation animation (X can be of 3 different values depending on rotation). I tried over 40 on...() functions like onAttachedToWindow() but they are all called too early. Waiting some time before starting is not good since I will have latency during normal start up and the waiting time is not well defined.

Since I am part of the system I have one solution by adding some codes deep in the window manager which I can ask to know if system rotation animation is running, but it is not elegant and is not a solution for any "normal" app. I also want to keep the rotation animation. Just wondering if there is an event or function in the public API to use.

Answer 1

I would try a ViewTreeObserver with OnGlobalLayoutListener as described here: How can you tell when a layout has been drawn?

EDIT: I created a sample working implementation. It is capturing the screen after the orientation change as you asked for.

Not possible to get the status bar without root: (android development)how to implement screen grab with status bar in code

However, is possible to remove the blank space where the status bar goes: Android screenshot of activity with actionbar

public class MainActivity extends Activity
{
    private static int counter = 1;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final View root = getWindow().getDecorView();
        ViewTreeObserver vto = root.getViewTreeObserver();
        vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

            @Override
            public void onGlobalLayout()
            {
                root
                .getViewTreeObserver()
                .removeOnGlobalLayoutListener(this);

                takeScreenShot(root);
                ++counter;
            }

        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    private void takeScreenShot(View view)
    {
        String mPath = Environment.getExternalStorageDirectory().toString() 
                + "/" + "rotation" + String.valueOf(counter);   

        // create bitmap screen capture
        Bitmap bitmap;

        view.setDrawingCacheEnabled(true);
        bitmap = Bitmap.createBitmap(view.getDrawingCache());
        view.setDrawingCacheEnabled(false);

        OutputStream fout = null;
        File imageFile = new File(mPath);

        try {
            fout = new FileOutputStream(imageFile);
            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, fout);
            fout.flush();
            fout.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }   
}