AppDrawer: Add highlighting scrubbing and offset

When you drag the scrubber it now highlights that section differently
Also when you drag on the scrubber, instead of bringing the section
into view at any point, it will try to make it the 3 row from the bottom

Change-Id: I7cefaa24fb3c757f6e031247bb4a247473dde828

1 files changed, 37 insertions, 2 deletions

diff --git a/src/com/android/launcher3/AppDrawerScrubber.java b/src/com/android/launcher3/AppDrawerScrubber.java
index 706ddfe96..c65fd373d 100644
--- a/src/com/android/launcher3/AppDrawerScrubber.java
+++ b/src/com/android/launcher3/AppDrawerScrubber.java
@@ -20,9 +20,11 @@ import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.content.Context;
 import android.graphics.Color;
+import android.graphics.PointF;
 import android.graphics.drawable.ColorDrawable;
 import android.graphics.drawable.Drawable;
 import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.LinearSmoothScroller;
 import android.support.v7.widget.RecyclerView;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
@@ -261,8 +263,41 @@ public class AppDrawerScrubber extends LinearLayout {
 
             // get the index of the underlying list
             int adapterIndex = mSectionContainer.getAdapterIndex(mLastIndex, index);
-            mLayoutManager.smoothScrollToPosition(mListView, null,
-                    mAdapter.getPositionForSection(adapterIndex));
+            int itemIndex = mAdapter.getPositionForSection(adapterIndex);
+
+            // get any child's height since all children are the same height
+            int itemHeight = 0;
+            View child = mLayoutManager.getChildAt(0);
+            if (child != null) {
+                itemHeight = child.getMeasuredHeight();
+            }
+
+            if (itemHeight != 0) {
+                // scroll to the item such that there are 2 rows beneath it from the bottom
+                final int itemDiff = 2 * itemHeight;
+                LinearSmoothScroller scroller = new LinearSmoothScroller(mListView.getContext()) {
+                    @Override
+                    protected int getVerticalSnapPreference() {
+                        // position the item against the end of the list view
+                        return SNAP_TO_END;
+                    }
+
+                    @Override
+                    public PointF computeScrollVectorForPosition(int targetPosition) {
+                        return mLayoutManager.computeScrollVectorForPosition(targetPosition);
+                    }
+
+                    @Override
+                    public int calculateDyToMakeVisible(View view, int snapPreference) {
+                        int dy = super.calculateDyToMakeVisible(view, snapPreference);
+                        return dy - itemDiff;
+                    }
+                };
+                scroller.setTargetPosition(itemIndex);
+                mLayoutManager.startSmoothScroll(scroller);
+            }
+
+            mAdapter.setSectionTarget(adapterIndex);
 
             mLastIndex = index;
         }