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Commit f1b946ef authored by Vladislav Kaznacheev's avatar Vladislav Kaznacheev Committed by eray orçunus
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Fix huge bounce-back in ListView when double-flinging 

The bounce-back reliably happened when AbsListView.fling
was called with high enough velocity (>50000). Such values
caused integer overflow when squared in the course of some
ballistic calculations in OverScroller.fitOnBounceCurve.

Bug: 19056278
Change-Id: I35d5376c67bc6847955b44ee268e89bce2db81d0
parent 77668c73

core/java/android/widget/OverScroller.java

+8 −4
Original line number Diff line number Diff line
@@ -738,7 +738,7 @@ public class OverScroller { 
            // mStartTime has been set

            mFinished = false;

            mState = CUBIC;

            mStart = start;

            mCurrentPosition = mStart = start;

            mFinal = end;

            final int delta = start - end;

            mDeceleration = getDeceleration(delta);
@@ -805,7 +805,9 @@ public class OverScroller { 
        private void fitOnBounceCurve(int start, int end, int velocity) {

            // Simulate a bounce that started from edge

            final float durationToApex = - velocity / mDeceleration;

            final float distanceToApex = velocity * velocity / 2.0f / Math.abs(mDeceleration);

            // The float cast below is necessary to avoid integer overflow.

            final float velocitySquared = (float) velocity * velocity;

            final float distanceToApex = velocitySquared / 2.0f / Math.abs(mDeceleration);

            final float distanceToEdge = Math.abs(end - start);

            final float totalDuration = (float) Math.sqrt(

                    2.0 * (distanceToApex + distanceToEdge) / Math.abs(mDeceleration));
@@ -856,12 +858,14 @@ public class OverScroller { 


        private void onEdgeReached() {

            // mStart, mVelocity and mStartTime were adjusted to their values when edge was reached.

            float distance = mVelocity * mVelocity / (2.0f * Math.abs(mDeceleration));

            // The float cast below is necessary to avoid integer overflow.

            final float velocitySquared = (float) mVelocity * mVelocity;

            float distance = velocitySquared / (2.0f * Math.abs(mDeceleration));

            final float sign = Math.signum(mVelocity);



            if (distance > mOver) {

                // Default deceleration is not sufficient to slow us down before boundary

                 mDeceleration = - sign * mVelocity * mVelocity / (2.0f * mOver);

                 mDeceleration = - sign * velocitySquared / (2.0f * mOver);

                 distance = mOver;

            }