Android: How to detect when a scroll has ended

Question

I am using the onScroll method of GestureDetector.SimpleOnGestureListener to scroll a large bitmap on a canvas. When the scroll has ended I want to redraw the bitmap in case the user wants to scroll further ... off the edge of the bitmap, but I can't see how to detect when the scroll has ended (the user has lifted his finger from the screen).

e2.getAction() always seems to return the value 2 so that is no help. e2.getPressure seems to return fairly constant values (around 0.25) until the final onScroll call when the pressure seems to fall to about 0.13. I suppose I could detect this reduction in pressure, but this will be far from foolproof.

There must be a better way: can anyone help, please?

Answer 1

Here is how I solved the problem. Hope this helps.

// declare class member variables private GestureDetector mGestureDetector; private OnTouchListener mGestureListener; private boolean mIsScrolling = false;   public void initGestureDetection() {         // Gesture detection     mGestureDetector = new GestureDetector(new SimpleOnGestureListener() {         @Override         public boolean onDoubleTap(MotionEvent e) {             handleDoubleTap(e);             return true;         }          @Override         public boolean onSingleTapConfirmed(MotionEvent e) {             handleSingleTap(e);             return true;         }          @Override         public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {             // i'm only scrolling along the X axis             mIsScrolling = true;                             handleScroll(Math.round((e2.getX() - e1.getX())));             return true;         }          @Override         /**          * Don't know why but we need to intercept this guy and return true so that the other gestures are handled.          * https://code.google.com/p/android/issues/detail?id=8233          */         public boolean onDown(MotionEvent e) {             Log.d("GestureDetector --> onDown");             return true;         }     });      mGestureListener = new View.OnTouchListener() {         public boolean onTouch(View v, MotionEvent event) {              if (mGestureDetector.onTouchEvent(event)) {                 return true;             }              if(event.getAction() == MotionEvent.ACTION_UP) {                 if(mIsScrolling ) {                     Log.d("OnTouchListener --> onTouch ACTION_UP");                     mIsScrolling  = false;                     handleScrollFinished();                 };             }              return false;         }     };      // attach the OnTouchListener to the image view     mImageView.setOnTouchListener(mGestureListener); }