Fix nested cross-scrolling for ScrollView/HorizontalScrollView

Bug 6429006

Disallow intercepting touch events for parents of
ScrollView/HorizontalScrollView when scrolling begins. Properly
respect touch slop when the child of a ScrollView does not accept
touch events.

Change-Id: I2ce503ad5104d450829ed58cd2748c9163e020d3

1 files changed, 26 insertions, 5 deletions

diff --git a/core/java/android/widget/ScrollView.java b/core/java/android/widget/ScrollView.java
index 0f0dbae03e37..f912c6625621 100644
--- a/core/java/android/widget/ScrollView.java
+++ b/core/java/android/widget/ScrollView.java
@@ -482,6 +482,10 @@ public class ScrollView extends FrameLayout {
                     if (mScrollStrictSpan == null) {
                         mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll");
                     }
+                    final ViewParent parent = getParent();
+                    if (parent != null) {
+                        parent.requestDisallowInterceptTouchEvent(true);
+                    }
                 }
                 break;
             }
@@ -546,10 +550,15 @@ public class ScrollView extends FrameLayout {
 
         switch (action & MotionEvent.ACTION_MASK) {
             case MotionEvent.ACTION_DOWN: {
-                mIsBeingDragged = getChildCount() != 0;
-                if (!mIsBeingDragged) {
+                if (getChildCount() == 0) {
                     return false;
                 }
+                if ((mIsBeingDragged = !mScroller.isFinished())) {
+                    final ViewParent parent = getParent();
+                    if (parent != null) {
+                        parent.requestDisallowInterceptTouchEvent(true);
+                    }
+                }
 
                 /*
                  * If being flinged and user touches, stop the fling. isFinished
@@ -569,11 +578,23 @@ public class ScrollView extends FrameLayout {
                 break;
             }
             case MotionEvent.ACTION_MOVE:
+                final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
+                final int y = (int) ev.getY(activePointerIndex);
+                int deltaY = mLastMotionY - y;
+                if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
+                    final ViewParent parent = getParent();
+                    if (parent != null) {
+                        parent.requestDisallowInterceptTouchEvent(true);
+                    }
+                    mIsBeingDragged = true;
+                    if (deltaY > 0) {
+                        deltaY -= mTouchSlop;
+                    } else {
+                        deltaY += mTouchSlop;
+                    }
+                }
                 if (mIsBeingDragged) {
                     // Scroll to follow the motion event
-                    final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
-                    final int y = (int) ev.getY(activePointerIndex);
-                    final int deltaY = mLastMotionY - y;
                     mLastMotionY = y;
 
                     final int oldX = mScrollX;