Fix bug where scroll position jumps when in overscroll.

When bouncing between top/bottom overscroll, mDistance calculation
allows it to increase without bounds. This solution resets
mDistance to 0 for the edge that is not being overscrolled.

Bug: 78364220
Change-Id: I8371b3aee37e82d40aaa6adc2473a87f2b69931c

src/com/android/launcher3/views/SpringRelativeLayout.java

@@ -24,7 +24,6 @@ import android.support.annotation.NonNull;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.RecyclerView.EdgeEffectFactory;
 import android.util.AttributeSet;
-import android.util.Log;
 import android.util.SparseBooleanArray;
 import android.view.View;
 import android.widget.EdgeEffect;
@@ -58,6 +57,7 @@ public class SpringRelativeLayout extends RelativeLayout {
     private final SpringAnimation mSpring;
 
     private float mDampedScrollShift = 0;
+    private SpringEdgeEffect mActiveEdge;
 
     public SpringRelativeLayout(Context context) {
         this(context, null);
@@ -90,6 +90,13 @@ public class SpringRelativeLayout extends RelativeLayout {
         return super.drawChild(canvas, child, drawingTime);
     }
 
+    private void setActiveEdge(SpringEdgeEffect edge) {
+        if (mActiveEdge != edge && mActiveEdge != null) {
+            mActiveEdge.mDistance = 0;
+        }
+        mActiveEdge = edge;
+    }
+
     private void setDampedScrollShift(float shift) {
         if (shift != mDampedScrollShift) {
             mDampedScrollShift = shift;
@@ -144,6 +151,7 @@ public class SpringRelativeLayout extends RelativeLayout {
 
         @Override
         public void onPull(float deltaDistance, float displacement) {
+            setActiveEdge(this);
             mDistance += deltaDistance * (mVelocityMultiplier / 3f);
             setDampedScrollShift(mDistance * getHeight());
         }