android - Adding natural dragging effect to ImageView same as Facebook Messanger chat heads using Rebound library

Question

I am developing one app where I am dragging around my ImageView in Activity. I have configured Facebook Rebound library for spring animation which is originally used in Facebook Messenger's chat heads animations. I want to add this kind of animations to my ImageView when I drag it. VIDEO

So far I am able to get spring animation when I touch ImageView (implemented spring on rootview), this is my code. How can I implement that natural type of dragging effect to my ImageView.

public class MainTry extends Activity {

    int windowwidth;
    int windowheight;

    private LayoutParams layoutParams;
    private final BaseSpringSystem mSpringSystem = SpringSystem.create();
    private FrameLayout mRootView;
    private Spring spring;
    private View mImageView;
    private VelocityTracker velocity = null;
    private float dx;
    private float dy;
    private View rootView;
    private ImageView img;

    @Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout);

    // Create a system to run the physics loop for a set of springs.
    SpringSystem springSystem = SpringSystem.create();

    // Add a spring to the system.
    spring = springSystem.createSpring();

    rootView = getWindow().getDecorView()
            .findViewById(android.R.id.content);

    windowwidth = getWindowManager().getDefaultDisplay().getWidth();
    windowheight = getWindowManager().getDefaultDisplay().getHeight();
    img = (ImageView) findViewById(R.id.imageView2);

    rootView.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // spring.setEndValue(1);
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                // spring.setEndValue(0);
                break;
            }
            return true;
        }
    });
    // Add a listener to observe the motion of the spring.
    spring.addListener(new SimpleSpringListener() {

        @Override
        public void onSpringUpdate(Spring spring) {
            // You can observe the updates in the spring
            // state by asking its current value in onSpringUpdate.
            float value = (float) spring.getCurrentValue();
            float scale = .5f - (value * 0.1f);
            img.setScaleX(scale);
            img.setScaleY(scale);
        }
    });
    // spring.setEndValue(1);

    img.setOnTouchListener(new View.OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            LayoutParams layoutParams = (LayoutParams) img
                    .getLayoutParams();

            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                dx = event.getRawX() - 10;
                dy = event.getRawY() - 10;

                if (velocity == null) {
                    // Retrieve a new VelocityTracker object to watch the
                    // velocity of a motion.
                    velocity = VelocityTracker.obtain();
                } else {
                    // Reset the velocity tracker back to its initial state.
                    velocity.clear();
                }
                break;
            case MotionEvent.ACTION_MOVE:
                dx = event.getRawX() - 10;
                dy = event.getRawY() - 10;


                velocity.addMovement(event);
                spring.setVelocity(velocity.getYVelocity());
                spring.setCurrentValue(dy);
                spring.setEndValue(dy);


                layoutParams.leftMargin = (int) dx - 10;
                layoutParams.topMargin = (int) dy - 10;
                img.setLayoutParams(layoutParams);
                break;
            case MotionEvent.ACTION_CANCEL:
                break;
            case MotionEvent.ACTION_UP:
                velocity.addMovement(event);
                spring.setVelocity(velocity.getYVelocity());
                spring.setCurrentValue(event.getRawY() - 10);
                spring.setEndValue(0);

                break;

            default:
                break;
            }
            return true;
        }
    });

}

@Override
public void onResume() {
    super.onResume();
}

@Override
public void onPause() {
    super.onPause();
}


}

Answer 1

what about this:

class V extends View implements SpringListener {
    private static final int NUM_ELEMS = 4;
    private Spring[] mXSprings = new Spring[NUM_ELEMS];
    private Spring[] mYSprings = new Spring[NUM_ELEMS];
    private Paint mPaint = new Paint();
    private Bitmap mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);

    public V(Context context) {
        super(context);
        SpringSystem ss = SpringSystem.create();

        Spring s;
        for (int i = 0; i < NUM_ELEMS; i++) {
            s = ss.createSpring();
            s.setSpringConfig(new MySpringConfig(200, i == 0? 8 : 15 + i * 2, i, true));
            s.addListener(this);
            mXSprings[i] = s;

            s = ss.createSpring();
            s.setSpringConfig(new MySpringConfig(200, i == 0? 8 : 15 + i * 2, i, false));
            s.addListener(this);
            mYSprings[i] = s;
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        mXSprings[0].setCurrentValue(w / 2);
        mYSprings[0].setCurrentValue(0);

        mXSprings[0].setEndValue(w / 2);
        mYSprings[0].setEndValue(h / 2);
    }

    @Override
    public void onSpringActivate(Spring s) {
    }

    @Override
    public void onSpringAtRest(Spring s) {
    }

    @Override
    public void onSpringEndStateChange(Spring s) {
    }

    @Override
    public void onSpringUpdate(Spring s) {
        MySpringConfig cfg = (MySpringConfig) s.getSpringConfig();
        if (cfg.index < NUM_ELEMS - 1) {
            Spring[] springs = cfg.horizontal? mXSprings : mYSprings;
            springs[cfg.index + 1].setEndValue(s.getCurrentValue());
        }
        if (cfg.index == 0) {
            invalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mXSprings[0].setEndValue(event.getX());
        mYSprings[0].setEndValue(event.getY());
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        for (int i = NUM_ELEMS - 1; i >= 0; i--) {
            mPaint.setAlpha(i == 0? 255 : 192 - i * 128 / NUM_ELEMS);
            canvas.drawBitmap(mBitmap, 
                    (float) mXSprings[i].getCurrentValue() - mBitmap.getWidth() / 2,
                    (float) mYSprings[i].getCurrentValue() - mBitmap.getHeight() / 2,
                    mPaint);
        }
    }

    class MySpringConfig extends SpringConfig {
        int index;
        boolean horizontal;
        public MySpringConfig(double tension, double friction, int index, boolean horizontal) {
            super(tension, friction);
            this.index = index;
            this.horizontal = horizontal;
        }
    }
}