question: @ Override public boolean onTouchEvent ( @ NonNull MotionEvent event ) { if ( ! isEnabled ( ) ) { return false ; } int pointerIndex ; final int action = event . getAction ( ) ; switch ( action & MotionEvent . ACTION_MASK ) { case MotionEvent . ACTION_DOWN : mActivePointerId = event . getPointerId ( event . getPointerCount ( ) - 1 ) ; pointerIndex = event . findPointerIndex ( mActivePointerId ) ; mDownMotionX = event . getX ( pointerIndex ) ; pressedThumb = evalPressedThumb ( mDownMotionX ) ; if ( pressedThumb == null ) { return super . onTouchEvent ( event ) ; } setPressed ( true ) ; invalidate ( ) ; onStartTrackingTouch ( ) ; trackTouchEvent ( event ) ; attemptClaimDrag ( ) ; break ; case MotionEvent . ACTION_MOVE : if ( pressedThumb != null ) { if ( mIsDragging ) { trackTouchEvent ( event ) ; } else { pointerIndex = event . findPointerIndex ( mActivePointerId ) ; final float x = event . getX ( pointerIndex ) ; if ( Math . abs ( x - mDownMotionX ) > mScaledTouchSlop ) { setPressed ( true ) ; invalidate ( ) ; onStartTrackingTouch ( ) ; trackTouchEvent ( event ) ; attemptClaimDrag ( ) ; } } if ( notifyWhileDragging && listener != null ) { listener . onRangeSeekBarValuesChanged ( this , getSelectedMinValue ( ) , getSelectedMaxValue ( ) ) ; } } break ; case MotionEvent . ACTION_UP : if ( mIsDragging ) { trackTouchEvent ( event ) ; onStopTrackingTouch ( ) ; setPressed ( false ) ; } else { onStartTrackingTouch ( ) ; trackTouchEvent ( event ) ; onStopTrackingTouch ( ) ; } pressedThumb = null ; invalidate ( ) ; if ( listener != null ) { listener . onRangeSeekBarValuesChanged ( this , getSelectedMinValue ( ) , getSelectedMaxValue ( ) ) ; } break ; case MotionEvent . ACTION_POINTER_DOWN : { final int index = event . getPointerCount ( ) - 1 ; mDownMotionX = event . getX ( index ) ; mActivePointerId = event . getPointerId ( index ) ; invalidate ( ) ; break ; } case MotionEvent . ACTION_POINTER_UP : onSecondaryPointerUp ( event ) ; invalidate ( ) ; break ; case MotionEvent . ACTION_CANCEL : if ( mIsDragging ) { onStopTrackingTouch ( ) ; setPressed ( false ) ; } invalidate ( ) ; break ; } return true ; }
target:  Handles thumb selection and movement. Notifies listener callback on certain events.