Introduced overscrolling for the panel expansion

Notifications now overscroll in a rubberbandy motion when expanding.

Bug: 14486987
Change-Id: I5ad47027adab10d6996e70f489e8c2550220e224

packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java

@@ -21,9 +21,7 @@ import android.animation.AnimatorListenerAdapter;
 import android.animation.ObjectAnimator;
 import android.animation.ValueAnimator;
 import android.content.Context;
-import android.graphics.Path;
 import android.util.AttributeSet;
-import android.util.Log;
 import android.view.MotionEvent;
 import android.view.VelocityTracker;
 import android.view.View;
@@ -32,7 +30,6 @@ import android.view.ViewTreeObserver;
 import android.view.accessibility.AccessibilityEvent;
 import android.view.animation.AnimationUtils;
 import android.view.animation.Interpolator;
-import android.view.animation.PathInterpolator;
 import android.widget.LinearLayout;
 
 import com.android.systemui.R;
@@ -645,6 +642,23 @@ public class NotificationPanelView extends PanelView implements
         mNotificationStackScroller.onExpansionStopped();
     }
 
+    @Override
+    protected void onOverExpansionChanged(float overExpansion) {
+        float currentOverScroll = mNotificationStackScroller.getCurrentOverScrolledPixels(true);
+        mNotificationStackScroller.setOverScrolledPixels(currentOverScroll + overExpansion
+                        - mOverExpansion, true /* onTop */, false /* animate */);
+        super.onOverExpansionChanged(overExpansion);
+    }
+
+    @Override
+    protected void onTrackingStopped() {
+        super.onTrackingStopped();
+        mOverExpansion = 0.0f;
+        mNotificationStackScroller.setOverScrolledPixels(0.0f, true /* onTop */,
+                true /* animate */);
+    }
+
+
     @Override
     public void onHeightChanged(ExpandableView view) {
         requestPanelHeightUpdate();

packages/SystemUI/src/com/android/systemui/statusbar/phone/PanelView.java

@@ -38,6 +38,7 @@ import java.io.PrintWriter;
 public class PanelView extends FrameLayout {
     public static final boolean DEBUG = PanelBar.DEBUG;
     public static final String TAG = PanelView.class.getSimpleName();
+    protected float mOverExpansion;
 
     private final void logf(String fmt, Object... args) {
         Log.v(TAG, (mViewName != null ? (mViewName + ": ") : "") + String.format(fmt, args));
@@ -403,6 +404,11 @@ public class PanelView extends FrameLayout {
     public void setExpandedHeightInternal(float h) {
         float fh = getMaxPanelHeight();
         mExpandedHeight = Math.min(fh, h);
+        float overExpansion = h - fh;
+        overExpansion = Math.max(0, overExpansion);
+        if (overExpansion != mOverExpansion) {
+            onOverExpansionChanged(overExpansion);
+        }
 
         if (DEBUG) {
             logf("setExpansion: height=%.1f fh=%.1f tracking=%s", h, fh, mTracking ? "T" : "f");
@@ -412,6 +418,10 @@ public class PanelView extends FrameLayout {
         mExpandedFraction = Math.min(1f, (fh == 0) ? 0 : h / fh);
     }
 
+    protected void onOverExpansionChanged(float overExpansion) {
+        mOverExpansion = overExpansion;
+    }
+
     protected void onHeightUpdated(float expandedHeight) {
         requestLayout();
     }