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Commit 8497369c authored by undefined's avatar undefined Committed by Steve Kondik
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Improve scrolling cache 

Scrolling cache helps make short scrolls/flings smooth but will
cause stutter when long flings are made. This patch disables
scrolling cache when long flings are made.

This patch also fixes a related bug where scrolling cache will
not be enabled properly when transitioning from flinging to scrolling.

Patch Set 2: Calculate threshold based on maximum velocity (Sang Tae Park)

Credits: Pawit Pornkitprasan

Change-Id: Iad52a35120212c871ffd35df6184aeb678ee44aa
parent 562ca17c

core/java/android/widget/AbsListView.java

+14 −2
Original line number Diff line number Diff line
@@ -604,6 +604,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te 
    Runnable mPositionScrollAfterLayout;

    private int mMinimumVelocity;

    private int mMaximumVelocity;

    private int mDecacheThreshold;

    private float mVelocityScale = 1.0f;



    final boolean[] mIsScrap = new boolean[1];
@@ -861,6 +862,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te 
        mTouchSlop = configuration.getScaledTouchSlop();

        mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();

        mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();

        mDecacheThreshold = mMaximumVelocity / 2;

        mOverscrollDistance = configuration.getScaledOverscrollDistance();

        mOverflingDistance = configuration.getScaledOverflingDistance();
@@ -4345,7 +4347,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te 
                    // Keep the fling alive a little longer

                    postDelayed(this, FLYWHEEL_TIMEOUT);

                } else {

                    endFling();

                    endFling(false); // Don't disable the scrolling cache right after it was enabled

                    mTouchMode = TOUCH_MODE_SCROLL;

                    reportScrollStateChange(OnScrollListener.SCROLL_STATE_TOUCH_SCROLL);

                }
@@ -4359,6 +4361,11 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te 
        }



        void start(int initialVelocity) {

            if (Math.abs(initialVelocity) > mDecacheThreshold) {

                // For long flings, scrolling cache causes stutter, so don't use it

                clearScrollingCache();

            }



            int initialY = initialVelocity < 0 ? Integer.MAX_VALUE : 0;

            mLastFlingY = initialY;

            mScroller.setInterpolator(null);
@@ -4431,12 +4438,17 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te 
        }



        void endFling() {

            endFling(true);

        }



        void endFling(boolean clearCache) {

            mTouchMode = TOUCH_MODE_REST;



            removeCallbacks(this);

            removeCallbacks(mCheckFlywheel);



            reportScrollStateChange(OnScrollListener.SCROLL_STATE_IDLE);

            if (clearCache)

                clearScrollingCache();

            mScroller.abortAnimation();