Android onfling prob

Question

I want to add a fling action on a LinearLayout. I have used the following code for this purpose.

public class NewsActivity extends Activity {

    ..........
    ...........
    private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;
    private GestureDetector gestureDetector;
    View.OnTouchListener gestureListener;



    @Override
    public void onCreate(Bundle savedInstanceState) {

       .....................
       .....................
       .....................

       LinearLayout newDeailsBlock = (LinearLayout) findViewById(R.id.newdeailsblock);
       // Gesture detection
       gestureDetector = new GestureDetector(new MyGestureDetector());
       gestureListener = new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                // TODO Auto-generated method stub
                if (gestureDetector.onTouchEvent(event)) {
                    return true;
                }
                return false;
            }
        };
        newDeailsBlock.setOnTouchListener(gestureListener);
    }

    class MyGestureDetector extends SimpleOnGestureListener {
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            try {
                Log.d("move","Swipe test");
                if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                    return false;
                // right to left swipe
                if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {                
                    Log.d("move","Left Swipe");
                }  else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                    Toast.makeText(NewsActivity.this, "Right Swipe", Toast.LENGTH_SHORT).show();
                    Log.d("move","Right Swipe");
                }
            } catch (Exception e) {
                // nothing
            }
            return false;
        }

    }
}

But it is not working at all amd gestureDetector.onTouchEvent(event) is returning false. What is the problem in my code?

Answer 1

Try having your Activity extend the below abstract class instead, and then implement the abstract methods next() and previous() with the functionality you want for the fling.

public abstract class SwipeActivity extends Activity {
    private static final int SWIPE_MIN_DISTANCE = 120;
    private static final int SWIPE_MAX_OFF_PATH = 250;
    private static final int SWIPE_THRESHOLD_VELOCITY = 200;
    private GestureDetector gestureDetector;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        gestureDetector = new GestureDetector( new SwipeDetector() );
    }

    private class SwipeDetector extends SimpleOnGestureListener {       
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {

            // Check movement along the Y-axis. If it exceeds SWIPE_MAX_OFF_PATH, then dismiss the swipe.
            if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
                return false;

            // Swipe from right to left.
            // The swipe needs to exceed a certain distance (SWIPE_MIN_DISTANCE) and a certain velocity (SWIPE_THRESHOLD_VELOCITY).
            if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                next();
                return true;
            }

            // Swipe from left to right.
            // The swipe needs to exceed a certain distance (SWIPE_MIN_DISTANCE) and a certain velocity (SWIPE_THRESHOLD_VELOCITY).
            if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                previous();
                return true;
            }

            return false;
        }
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        //TouchEvent dispatcher.
        if (gestureDetector != null) {
            if (gestureDetector.onTouchEvent(ev))
                //If the gestureDetector handles the event, a swipe has been executed and no more needs to be done.
                return true;
        }
        return super.dispatchTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return gestureDetector.onTouchEvent(event);
    }

    protected abstract void previous();
    protected abstract void next();
}