Android - HorizontalScrollView within ScrollView Touch Handling?

Update: I figured this out. On my ScrollView, I needed to override the onInterceptTouchEvent method to only intercept the touch event if the Y motion is > the X motion. It seems like the default behavior of a ScrollView is to intercept the touch event whenever there is ANY Y motion.So with the fix, the ScrollView will only intercept the event if the user is deliberately scrolling in the Y direction and in that case pass off the ACTION_CANCEL to the children.

Here is the code for my Scroll View class that contains the HorizontalScrollView: public class CustomScrollView extends ScrollView { private GestureDetector gestureDetector; View. OnTouchListener gestureListener; public CustomScrollView(Context context, AttributeSet attrs) { super(context, attrs); gestureDetector = new GestureDetector(new YScrollDetector()); setFadingEdgeLength(0); } @Override public boolean onTouchEvent(MotionEvent ev) { return super. OnTouchEvent(ev); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { //Call super first because it does some hidden motion event handling boolean result = super.

OnInterceptTouchEvent(ev); //Now see if we are scrolling vertically with the custom gesture detector if (gestureDetector. OnTouchEvent(ev)) { return result; } //If not scrolling vertically (more y than x), don't hijack the event. Else { return false; } } // Return false if we're scrolling in the x direction class YScrollDetector extends SimpleOnGestureListener { @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { try { if (Math.

Abs(distanceY) > Math. Abs(distanceX)) { return true; } else { return false; } } catch (Exception e) { // nothing } return false; } } }.

You, sir, are a God to me. Thank you very much. – sniurkst Dec 7 '10 at 7:55 Good stuff, very useful for any scrollable view nesting.

Minor points on the code, though: You can actually simplify the entire onIntercept method to just this: return super. OnInterceptTouchEvent(ev) && mGestureDetector. OnTouchEvent(ev); Also, the try/catch in the onScroll is really unnecessary (exactly what exception can be thrown there?); it'd suffice to replace the entire method with return (Math.

Abs(distanceY) > Math. Abs(distanceX)). – Yoni Samlan Sep 15 at 21:17 Great work, thanks!

– Zsombor ErdÅ‘dy-Nagy Oct 26 at 16:29.

Thank you Joel for giving me a clue on how to resolve this problem. I have simplified the code(without need for a GestureDetector) to achieve the same effect: public class VerticalScrollView extends ScrollView { private float xDistance, yDistance, lastX, lastY; public VerticalScrollView(Context context, AttributeSet attrs) { super(context, attrs); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent. ACTION_DOWN: xDistance = yDistance = 0f; lastX = ev.getX(); lastY = ev.getY(); break; case MotionEvent.

ACTION_MOVE: final float curX = ev.getX(); final float curY = ev.getY(); xDistance += Math. Abs(curX - lastX); yDistance += Math. Abs(curY - lastY); lastX = curX; lastY = curY; if(xDistance > yDistance) return false; } return super.

OnInterceptTouchEvent(ev); } }.

Update: I figured this out. On my ScrollView, I needed to override the onInterceptTouchEvent method to only intercept the touch event if the Y motion is > the X motion. It seems like the default behavior of a ScrollView is to intercept the touch event whenever there is ANY Y motion.

So with the fix, the ScrollView will only intercept the event if the user is deliberately scrolling in the Y direction and in that case pass off the ACTION_CANCEL to the children.

Thank you Joel for giving me a clue on how to resolve this problem.

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