fix: touch velocities should be ignored when a view receives the ACTION_CANCEL event

Author: lzls

gallery-viewer/src/main/java/com/liuzhenlin/galleryviewer/GestureImageView.java

@@ -517,18 +517,20 @@ public boolean onTouchEvent(MotionEvent event) {
                     }
 
                     // No scaling is needed below
-                    mVelocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
-                    final float vx = mVelocityTracker.getXVelocity(mActivePointerId);
-                    final float vy = mVelocityTracker.getYVelocity(mActivePointerId);
-                    // If one of the velocities is not less than our minimum fling velocity,
-                    // treat it as fling as user raises up his/her last finger that is
-                    // touching the screen.
-                    if ((Math.abs(vx) >= mMinimumFlingVelocity
-                            || Math.abs(vy) >= mMinimumFlingVelocity)) {
-                        cancelImageTransformations();
-                        getImageTransformer().fling(translationX, translationY, vx, vy,
-                                width, height, mImageBounds.width(), mImageBounds.height());
-                        break;
+                    if (actionMasked == MotionEvent.ACTION_UP) {
+                        mVelocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
+                        final float vx = mVelocityTracker.getXVelocity(mActivePointerId);
+                        final float vy = mVelocityTracker.getYVelocity(mActivePointerId);
+                        // If one of the velocities is not less than our minimum fling velocity,
+                        // treat it as fling as user raises up his/her last finger that is
+                        // touching the screen.
+                        if ((Math.abs(vx) >= mMinimumFlingVelocity
+                                || Math.abs(vy) >= mMinimumFlingVelocity)) {
+                            cancelImageTransformations();
+                            getImageTransformer().fling(translationX, translationY, vx, vy,
+                                    width, height, mImageBounds.width(), mImageBounds.height());
+                            break;
+                        }
                     }
                     // Not else!
                     // Here regard it as a normal scroll

sliding-drawer-layout/src/main/java/com/liuzhenlin/slidingdrawerlayout/SlidingDrawerLayout.java

@@ -1945,7 +1945,8 @@ public boolean onTouchEvent(MotionEvent event) {
             mVelocityTracker = VelocityTracker.obtain();
         mVelocityTracker.addMovement(event);
 
-        switch (event.getAction() & MotionEvent.ACTION_MASK) {
+        final int actionMasked = event.getAction() & MotionEvent.ACTION_MASK;
+        switch (actionMasked) {
             case MotionEvent.ACTION_POINTER_DOWN:
                 onPointerDown(event);
                 break;
@@ -1987,16 +1988,18 @@ public boolean onTouchEvent(MotionEvent event) {
                             break;
                         }
 
-                        mVelocityTracker.computeCurrentVelocity(1000);
-                        final float vx = mVelocityTracker.getXVelocity(mActivePointerId);
-                        if (mShownDrawer == mLeftDrawer && vx >= mMinimumFlingVelocity
-                                || mShownDrawer == mRightDrawer && vx <= -mMinimumFlingVelocity) {
-                            openDrawerInternal(mShownDrawer, true);
-                            break;
-                        } else if (mShownDrawer == mLeftDrawer && vx <= -mMinimumFlingVelocity
-                                || mShownDrawer == mRightDrawer && vx >= mMinimumFlingVelocity) {
-                            closeDrawer(true);
-                            break;
+                        if (actionMasked == MotionEvent.ACTION_UP) {
+                            mVelocityTracker.computeCurrentVelocity(1000);
+                            final float vx = mVelocityTracker.getXVelocity(mActivePointerId);
+                            if (mShownDrawer == mLeftDrawer && vx >= mMinimumFlingVelocity
+                                    || mShownDrawer == mRightDrawer && vx <= -mMinimumFlingVelocity) {
+                                openDrawerInternal(mShownDrawer, true);
+                                break;
+                            } else if (mShownDrawer == mLeftDrawer && vx <= -mMinimumFlingVelocity
+                                    || mShownDrawer == mRightDrawer && vx >= mMinimumFlingVelocity) {
+                                closeDrawer(true);
+                                break;
+                            }
                         }
 
                         if (mScrollPercent >= 0.5f) {