Question

What Android Api is used to get the scrolling to the left or to the right on the start screen on Android?

Answer 1

The simplest way is by detecting a “Fling” gesture. The android API has a built in detector for basic gestures like flinging, scrolling, long press, double tap, pinch zoom, etc.

The documentation is available at http://developer.android.com/reference/android/view/GestureDetector.html.

What you do is create an instance of GestureDetector, override the onTouchEvent method of the view you are interested in detecting gestures for, and pass the MotionEvent to the GestureDetector.

You also have to supply a OnGestureListener implementation (easiest to extend SimpleOnGestureListener) to the GestureDetector and that will handle all of your gesture events.

Example:

class MyView extends View
{
    GestureDetector mGestureDetect;

    public MyView(Context context)
    {
        super(context);
        mGestureDetect = new GestureDetector(new SimpleOnGestureListener()
        {

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) 
        {
        //check if the fling was in the direction you were interested in
        if(e1.getX() - e2.getX() > 0)
        {
        //Do something here
        }
        //fast enough?
        if(velocityX > 50)
        {
        //etc etc
        }

        return true;
        }
        }
    }

    public boolean onTouchEvent(MotionEvent ev)
    {
        mGestureDetector.onTocuhEvent(ev);
        return true;
    }
}