Refactor AbsListView position scrollers for better abstraction

The AbsListView sub-scroller knows nothing about layout. That's now
handled by ListView and GridView, with subclasses of AbsListView using
the default PositionScroller. Removes unnecessary (unreleased) APIs.

Also fixes a bounds check that was using the item position rather than
the child view position.

BUG: 13006641
Change-Id: I2adb0f15623e32295facf81f5ada974083ba03ce

api/current.txt

@@ -31628,12 +31628,10 @@ package android.widget {
     method public int getCheckedItemPosition();
     method public android.util.SparseBooleanArray getCheckedItemPositions();
     method public int getChoiceMode();
-    method public int getFirstPositionForRow(int);
     method public int getListPaddingBottom();
     method public int getListPaddingLeft();
     method public int getListPaddingRight();
     method public int getListPaddingTop();
-    method public int getRowForPosition(int);
     method public android.view.View getSelectedView();
     method public android.graphics.drawable.Drawable getSelector();
     method public java.lang.CharSequence getTextFilter();

core/java/android/widget/GridView.java

@@ -35,6 +35,8 @@ import android.view.accessibility.AccessibilityNodeInfo;
 import android.view.accessibility.AccessibilityNodeInfo.CollectionInfo;
 import android.view.accessibility.AccessibilityNodeInfo.CollectionItemInfo;
 import android.view.animation.GridLayoutAnimationController;
+import android.widget.AbsListView.AbsPositionScroller;
+import android.widget.ListView.ListViewPositionScroller;
 import android.widget.RemoteViews.RemoteView;
 
 import java.lang.annotation.Retention;
@@ -1027,13 +1029,8 @@ public class GridView extends AbsListView {
     }
 
     @Override
-    public int getRowForPosition(int position) {
-        return position / mNumColumns;
-    }
-
-    @Override
-    public int getFirstPositionForRow(int row) {
-        return row * mNumColumns;
+    AbsPositionScroller createPositionScroller() {
+        return new GridViewPositionScroller();
     }
 
     @Override
@@ -2357,4 +2354,33 @@ public class GridView extends AbsListView {
         final CollectionItemInfo itemInfo = CollectionItemInfo.obtain(column, 1, row, 1, isHeading);
         info.setCollectionItemInfo(itemInfo);
     }
+
+    /**
+     * Sub-position scroller that understands the layout of a GridView.
+     */
+    class GridViewPositionScroller extends AbsSubPositionScroller {
+        @Override
+        public int getRowForPosition(int position) {
+            return position / mNumColumns;
+        }
+
+        @Override
+        public int getFirstPositionForRow(int row) {
+            return row * mNumColumns;
+        }
+
+        @Override
+        public int getHeightForRow(int row) {
+            final int firstRowPosition = row * mNumColumns;
+            final int lastRowPosition = Math.min(getCount(), firstRowPosition + mNumColumns);
+            int maxHeight = 0;
+            for (int i = firstRowPosition; i < lastRowPosition; i++) {
+                final int height = getHeightForPosition(i);
+                if (height > maxHeight) {
+                    maxHeight = height;
+                }
+            }
+            return maxHeight;
+        }
+    }
 }

core/java/android/widget/ListView.java

@@ -3775,13 +3775,8 @@ public class ListView extends AbsListView {
     }
 
     @Override
-    public int getRowForPosition(int position) {
-        return position;
-    }
-
-    @Override
-    public int getFirstPositionForRow(int row) {
-        return row;
+    AbsPositionScroller createPositionScroller() {
+        return new ListViewPositionScroller();
     }
 
     @Override
@@ -3810,4 +3805,24 @@ public class ListView extends AbsListView {
         final CollectionItemInfo itemInfo = CollectionItemInfo.obtain(0, 1, position, 1, isHeading);
         info.setCollectionItemInfo(itemInfo);
     }
+
+    /**
+     * Sub-position scroller that understands the layout of a ListView.
+     */
+    class ListViewPositionScroller extends AbsSubPositionScroller {
+        @Override
+        public int getRowForPosition(int position) {
+            return position;
+        }
+
+        @Override
+        public int getFirstPositionForRow(int row) {
+            return row;
+        }
+
+        @Override
+        public int getHeightForRow(int row) {
+            return getHeightForPosition(row);
+        }
+    }
 }