src/com/android/launcher3/allapps/AllAppsRecyclerView.java - platform/packages/apps/Launcher3 - Git at Google

 /*
  * Copyright (C) 2015 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package com.android.launcher3.allapps;

 import android.content.Context;
 import android.content.res.Resources;
 import android.graphics.Canvas;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.support.v7.widget.RecyclerView;
 import android.util.AttributeSet;
 import android.view.View;

 import com.android.launcher3.BaseRecyclerView;
 import com.android.launcher3.BubbleTextView;
 import com.android.launcher3.DeviceProfile;
 import com.android.launcher3.R;
 import com.android.launcher3.Stats;
 import com.android.launcher3.Utilities;

 import java.util.List;

 /**
  * A RecyclerView with custom fast scroll support for the all apps view.
  */
 public class AllAppsRecyclerView extends BaseRecyclerView
         implements Stats.LaunchSourceProvider {

     private AlphabeticalAppsList mApps;
     private AllAppsFastScrollHelper mFastScrollHelper;
     private BaseRecyclerView.ScrollPositionState mScrollPosState =
             new BaseRecyclerView.ScrollPositionState();
     private int mNumAppsPerRow;

     // The specific icon heights that we use to calculate scroll
     private int mPredictionIconHeight;
     private int mIconHeight;

     // The empty-search result background
     private AllAppsBackgroundDrawable mEmptySearchBackground;
     private int mEmptySearchBackgroundTopOffset;

     private HeaderElevationController mElevationController;

     public AllAppsRecyclerView(Context context) {
         this(context, null);
     }

     public AllAppsRecyclerView(Context context, AttributeSet attrs) {
         this(context, attrs, 0);
     }

     public AllAppsRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
         this(context, attrs, defStyleAttr, 0);
     }

     public AllAppsRecyclerView(Context context, AttributeSet attrs, int defStyleAttr,
             int defStyleRes) {
         super(context, attrs, defStyleAttr);
         Resources res = getResources();
         addOnItemTouchListener(this);
         mScrollbar.setDetachThumbOnFastScroll();
         mEmptySearchBackgroundTopOffset = res.getDimensionPixelSize(
                 R.dimen.all_apps_empty_search_bg_top_offset);
     }

     /**
      * Sets the list of apps in this view, used to determine the fastscroll position.
      */
     public void setApps(AlphabeticalAppsList apps) {
         mApps = apps;
         mFastScrollHelper = new AllAppsFastScrollHelper(this, apps);
     }

     public void setElevationController(HeaderElevationController elevationController) {
         mElevationController = elevationController;
     }

     /**
      * Sets the number of apps per row in this recycler view.
      */
     public void setNumAppsPerRow(DeviceProfile grid, int numAppsPerRow) {
         mNumAppsPerRow = numAppsPerRow;

         RecyclerView.RecycledViewPool pool = getRecycledViewPool();
         int approxRows = (int) Math.ceil(grid.availableHeightPx / grid.allAppsIconSizePx);
         pool.setMaxRecycledViews(AllAppsGridAdapter.EMPTY_SEARCH_VIEW_TYPE, 1);
         pool.setMaxRecycledViews(AllAppsGridAdapter.SEARCH_MARKET_DIVIDER_VIEW_TYPE, 1);
         pool.setMaxRecycledViews(AllAppsGridAdapter.SEARCH_MARKET_VIEW_TYPE, 1);
         pool.setMaxRecycledViews(AllAppsGridAdapter.ICON_VIEW_TYPE, approxRows * mNumAppsPerRow);
         pool.setMaxRecycledViews(AllAppsGridAdapter.PREDICTION_ICON_VIEW_TYPE, mNumAppsPerRow);
         pool.setMaxRecycledViews(AllAppsGridAdapter.SECTION_BREAK_VIEW_TYPE, approxRows);
     }

     /**
      * Sets the heights of the icons in this view (for scroll calculations).
      */
     public void setPremeasuredIconHeights(int predictionIconHeight, int iconHeight) {
         mPredictionIconHeight = predictionIconHeight;
         mIconHeight = iconHeight;
     }

     /**
      * Scrolls this recycler view to the top.
      */
     public void scrollToTop() {
         // Ensure we reattach the scrollbar if it was previously detached while fast-scrolling
         if (mScrollbar.isThumbDetached()) {
             mScrollbar.reattachThumbToScroll();
         }
         scrollToPosition(0);
         if (mElevationController != null) {
             mElevationController.reset();
         }
     }

     /**
      * We need to override the draw to ensure that we don't draw the overscroll effect beyond the
      * background bounds.
      */
     @Override
     protected void dispatchDraw(Canvas canvas) {
         // Clip to ensure that we don't draw the overscroll effect beyond the background bounds
         canvas.clipRect(mBackgroundPadding.left, mBackgroundPadding.top,
                 getWidth() - mBackgroundPadding.right,
                 getHeight() - mBackgroundPadding.bottom);
         super.dispatchDraw(canvas);
     }

     @Override
     public void onDraw(Canvas c) {
         // Draw the background
         if (mEmptySearchBackground != null && mEmptySearchBackground.getAlpha() > 0) {
             c.clipRect(mBackgroundPadding.left, mBackgroundPadding.top,
                     getWidth() - mBackgroundPadding.right,
                     getHeight() - mBackgroundPadding.bottom);

             mEmptySearchBackground.draw(c);
         }

         super.onDraw(c);
     }

     @Override
     protected boolean verifyDrawable(Drawable who) {
         return who == mEmptySearchBackground || super.verifyDrawable(who);
     }

     @Override
     protected void onSizeChanged(int w, int h, int oldw, int oldh) {
         updateEmptySearchBackgroundBounds();
     }

     @Override
     public void fillInLaunchSourceData(View v, Bundle sourceData) {
         sourceData.putString(Stats.SOURCE_EXTRA_CONTAINER, Stats.CONTAINER_ALL_APPS);
         if (mApps.hasFilter()) {
             sourceData.putString(Stats.SOURCE_EXTRA_SUB_CONTAINER,
                     Stats.SUB_CONTAINER_ALL_APPS_SEARCH);
         } else {
             if (v instanceof BubbleTextView) {
                 BubbleTextView icon = (BubbleTextView) v;
                 int position = getChildPosition(icon);
                 if (position != NO_POSITION) {
                     List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
                     AlphabeticalAppsList.AdapterItem item = items.get(position);
                     if (item.viewType == AllAppsGridAdapter.PREDICTION_ICON_VIEW_TYPE) {
                         sourceData.putString(Stats.SOURCE_EXTRA_SUB_CONTAINER,
                                 Stats.SUB_CONTAINER_ALL_APPS_PREDICTION);
                         return;
                     }
                 }
             }
             sourceData.putString(Stats.SOURCE_EXTRA_SUB_CONTAINER,
                     Stats.SUB_CONTAINER_ALL_APPS_A_Z);
         }
     }

     public void onSearchResultsChanged() {
         // Always scroll the view to the top so the user can see the changed results
         scrollToTop();

         if (mApps.hasNoFilteredResults()) {
             if (mEmptySearchBackground == null) {
                 mEmptySearchBackground = new AllAppsBackgroundDrawable(getContext());
                 mEmptySearchBackground.setAlpha(0);
                 mEmptySearchBackground.setCallback(this);
                 updateEmptySearchBackgroundBounds();
             }
             mEmptySearchBackground.animateBgAlpha(1f, 150);
         } else if (mEmptySearchBackground != null) {
             // For the time being, we just immediately hide the background to ensure that it does
             // not overlap with the results
             mEmptySearchBackground.setBgAlpha(0f);
         }
     }

     /**
      * Maps the touch (from 0..1) to the adapter position that should be visible.
      */
     @Override
     public String scrollToPositionAtProgress(float touchFraction) {
         int rowCount = mApps.getNumAppRows();
         if (rowCount == 0) {
             return "";
         }

         // Stop the scroller if it is scrolling
         stopScroll();

         // Find the fastscroll section that maps to this touch fraction
         List<AlphabeticalAppsList.FastScrollSectionInfo> fastScrollSections =
                 mApps.getFastScrollerSections();
         AlphabeticalAppsList.FastScrollSectionInfo lastInfo = fastScrollSections.get(0);
         for (int i = 1; i < fastScrollSections.size(); i++) {
             AlphabeticalAppsList.FastScrollSectionInfo info = fastScrollSections.get(i);
             if (info.touchFraction > touchFraction) {
                 break;
             }
             lastInfo = info;
         }

         // Update the fast scroll
         int scrollY = getScrollTop(mScrollPosState);
         int availableScrollHeight = getAvailableScrollHeight(mApps.getNumAppRows());
         mFastScrollHelper.smoothScrollToSection(scrollY, availableScrollHeight, lastInfo);
         return lastInfo.sectionName;
     }

     @Override
     public void onFastScrollCompleted() {
         super.onFastScrollCompleted();
         mFastScrollHelper.onFastScrollCompleted();
     }

     @Override
     public void setAdapter(Adapter adapter) {
         super.setAdapter(adapter);
         mFastScrollHelper.onSetAdapter((AllAppsGridAdapter) adapter);
     }

     /**
      * Updates the bounds for the scrollbar.
      */
     @Override
     public void onUpdateScrollbar(int dy) {
         List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();

         // Skip early if there are no items or we haven't been measured
         if (items.isEmpty() || mNumAppsPerRow == 0) {
             mScrollbar.setThumbOffset(-1, -1);
             return;
         }

         // Find the index and height of the first visible row (all rows have the same height)
         int rowCount = mApps.getNumAppRows();
         getCurScrollState(mScrollPosState, -1);
         if (mScrollPosState.rowIndex < 0) {
             mScrollbar.setThumbOffset(-1, -1);
             return;
         }

         // Only show the scrollbar if there is height to be scrolled
         int availableScrollBarHeight = getAvailableScrollBarHeight();
         int availableScrollHeight = getAvailableScrollHeight(mApps.getNumAppRows());
         if (availableScrollHeight <= 0) {
             mScrollbar.setThumbOffset(-1, -1);
             return;
         }

         // Calculate the current scroll position, the scrollY of the recycler view accounts for the
         // view padding, while the scrollBarY is drawn right up to the background padding (ignoring
         // padding)
         int scrollY = getScrollTop(mScrollPosState);
         int scrollBarY = mBackgroundPadding.top +
                 (int) (((float) scrollY / availableScrollHeight) * availableScrollBarHeight);

         if (mScrollbar.isThumbDetached()) {
             int scrollBarX;
             if (Utilities.isRtl(getResources())) {
                 scrollBarX = mBackgroundPadding.left;
             } else {
                 scrollBarX = getWidth() - mBackgroundPadding.right - mScrollbar.getThumbWidth();
             }

             if (mScrollbar.isDraggingThumb()) {
                 // If the thumb is detached, then just update the thumb to the current
                 // touch position
                 mScrollbar.setThumbOffset(scrollBarX, (int) mScrollbar.getLastTouchY());
             } else {
                 int thumbScrollY = mScrollbar.getThumbOffset().y;
                 int diffScrollY = scrollBarY - thumbScrollY;
                 if (diffScrollY * dy > 0f) {
                     // User is scrolling in the same direction the thumb needs to catch up to the
                     // current scroll position.  We do this by mapping the difference in movement
                     // from the original scroll bar position to the difference in movement necessary
                     // in the detached thumb position to ensure that both speed towards the same
                     // position at either end of the list.
                     if (dy < 0) {
                         int offset = (int) ((dy * thumbScrollY) / (float) scrollBarY);
                         thumbScrollY += Math.max(offset, diffScrollY);
                     } else {
                         int offset = (int) ((dy * (availableScrollBarHeight - thumbScrollY)) /
                                 (float) (availableScrollBarHeight - scrollBarY));
                         thumbScrollY += Math.min(offset, diffScrollY);
                     }
                     thumbScrollY = Math.max(0, Math.min(availableScrollBarHeight, thumbScrollY));
                     mScrollbar.setThumbOffset(scrollBarX, thumbScrollY);
                     if (scrollBarY == thumbScrollY) {
                         mScrollbar.reattachThumbToScroll();
                     }
                 } else {
                     // User is scrolling in an opposite direction to the direction that the thumb
                     // needs to catch up to the scroll position.  Do nothing except for updating
                     // the scroll bar x to match the thumb width.
                     mScrollbar.setThumbOffset(scrollBarX, thumbScrollY);
                 }
             }
         } else {
             synchronizeScrollBarThumbOffsetToViewScroll(mScrollPosState, rowCount);
         }
     }

     /**
      * Returns the current scroll state of the apps rows.
      */
     protected void getCurScrollState(ScrollPositionState stateOut, int viewTypeMask) {
         stateOut.rowIndex = -1;
         stateOut.rowTopOffset = -1;
         stateOut.itemPos = -1;

         // Return early if there are no items or we haven't been measured
         List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
         if (items.isEmpty() || mNumAppsPerRow == 0) {
             return;
         }

         int childCount = getChildCount();
         for (int i = 0; i < childCount; i++) {
             View child = getChildAt(i);
             int position = getChildPosition(child);
             if (position != NO_POSITION) {
                 AlphabeticalAppsList.AdapterItem item = items.get(position);
                 if ((item.viewType & viewTypeMask) != 0) {
                     stateOut.rowIndex = item.rowIndex;
                     stateOut.rowTopOffset = getLayoutManager().getDecoratedTop(child);
                     stateOut.itemPos = position;
                     return;
                 }
             }
         }
         return;
     }

     @Override
     protected boolean supportsFastScrolling() {
         // Only allow fast scrolling when the user is not searching, since the results are not
         // grouped in a meaningful order
         return !mApps.hasFilter();
     }

     protected int getTop(int rowIndex) {
         if (getChildCount() == 0 || rowIndex <= 0) {
             return 0;
         }

         // The prediction bar icons have more padding, so account for that in the row offset
         return mPredictionIconHeight + (rowIndex - 1) * mIconHeight;
     }

     /**
      * Updates the bounds of the empty search background.
      */
     private void updateEmptySearchBackgroundBounds() {
         if (mEmptySearchBackground == null) {
             return;
         }

         // Center the empty search background on this new view bounds
         int x = (getMeasuredWidth() - mEmptySearchBackground.getIntrinsicWidth()) / 2;
         int y = mEmptySearchBackgroundTopOffset;
         mEmptySearchBackground.setBounds(x, y,
                 x + mEmptySearchBackground.getIntrinsicWidth(),
                 y + mEmptySearchBackground.getIntrinsicHeight());
     }
 }
	/*
	* Copyright (C) 2015 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package com.android.launcher3.allapps;

	import android.content.Context;
	import android.content.res.Resources;
	import android.graphics.Canvas;
	import android.graphics.drawable.Drawable;
	import android.os.Bundle;
	import android.support.v7.widget.RecyclerView;
	import android.util.AttributeSet;
	import android.view.View;

	import com.android.launcher3.BaseRecyclerView;
	import com.android.launcher3.BubbleTextView;
	import com.android.launcher3.DeviceProfile;
	import com.android.launcher3.R;
	import com.android.launcher3.Stats;
	import com.android.launcher3.Utilities;

	import java.util.List;

	/**
	* A RecyclerView with custom fast scroll support for the all apps view.
	*/
	public class AllAppsRecyclerView extends BaseRecyclerView
	implements Stats.LaunchSourceProvider {

	private AlphabeticalAppsList mApps;
	private AllAppsFastScrollHelper mFastScrollHelper;
	private BaseRecyclerView.ScrollPositionState mScrollPosState =
	new BaseRecyclerView.ScrollPositionState();
	private int mNumAppsPerRow;

	// The specific icon heights that we use to calculate scroll
	private int mPredictionIconHeight;
	private int mIconHeight;

	// The empty-search result background
	private AllAppsBackgroundDrawable mEmptySearchBackground;
	private int mEmptySearchBackgroundTopOffset;

	private HeaderElevationController mElevationController;

	public AllAppsRecyclerView(Context context) {
	this(context, null);
	}

	public AllAppsRecyclerView(Context context, AttributeSet attrs) {
	this(context, attrs, 0);
	}

	public AllAppsRecyclerView(Context context, AttributeSet attrs, int defStyleAttr) {
	this(context, attrs, defStyleAttr, 0);
	}

	public AllAppsRecyclerView(Context context, AttributeSet attrs, int defStyleAttr,
	int defStyleRes) {
	super(context, attrs, defStyleAttr);
	Resources res = getResources();
	addOnItemTouchListener(this);
	mScrollbar.setDetachThumbOnFastScroll();
	mEmptySearchBackgroundTopOffset = res.getDimensionPixelSize(
	R.dimen.all_apps_empty_search_bg_top_offset);
	}

	/**
	* Sets the list of apps in this view, used to determine the fastscroll position.
	*/
	public void setApps(AlphabeticalAppsList apps) {
	mApps = apps;
	mFastScrollHelper = new AllAppsFastScrollHelper(this, apps);
	}

	public void setElevationController(HeaderElevationController elevationController) {
	mElevationController = elevationController;
	}

	/**
	* Sets the number of apps per row in this recycler view.
	*/
	public void setNumAppsPerRow(DeviceProfile grid, int numAppsPerRow) {
	mNumAppsPerRow = numAppsPerRow;

	RecyclerView.RecycledViewPool pool = getRecycledViewPool();
	int approxRows = (int) Math.ceil(grid.availableHeightPx / grid.allAppsIconSizePx);
	pool.setMaxRecycledViews(AllAppsGridAdapter.EMPTY_SEARCH_VIEW_TYPE, 1);
	pool.setMaxRecycledViews(AllAppsGridAdapter.SEARCH_MARKET_DIVIDER_VIEW_TYPE, 1);
	pool.setMaxRecycledViews(AllAppsGridAdapter.SEARCH_MARKET_VIEW_TYPE, 1);
	pool.setMaxRecycledViews(AllAppsGridAdapter.ICON_VIEW_TYPE, approxRows * mNumAppsPerRow);
	pool.setMaxRecycledViews(AllAppsGridAdapter.PREDICTION_ICON_VIEW_TYPE, mNumAppsPerRow);
	pool.setMaxRecycledViews(AllAppsGridAdapter.SECTION_BREAK_VIEW_TYPE, approxRows);
	}

	/**
	* Sets the heights of the icons in this view (for scroll calculations).
	*/
	public void setPremeasuredIconHeights(int predictionIconHeight, int iconHeight) {
	mPredictionIconHeight = predictionIconHeight;
	mIconHeight = iconHeight;
	}

	/**
	* Scrolls this recycler view to the top.
	*/
	public void scrollToTop() {
	// Ensure we reattach the scrollbar if it was previously detached while fast-scrolling
	if (mScrollbar.isThumbDetached()) {
	mScrollbar.reattachThumbToScroll();
	}
	scrollToPosition(0);
	if (mElevationController != null) {
	mElevationController.reset();
	}
	}

	/**
	* We need to override the draw to ensure that we don't draw the overscroll effect beyond the
	* background bounds.
	*/
	@Override
	protected void dispatchDraw(Canvas canvas) {
	// Clip to ensure that we don't draw the overscroll effect beyond the background bounds
	canvas.clipRect(mBackgroundPadding.left, mBackgroundPadding.top,
	getWidth() - mBackgroundPadding.right,
	getHeight() - mBackgroundPadding.bottom);
	super.dispatchDraw(canvas);
	}

	@Override
	public void onDraw(Canvas c) {
	// Draw the background
	if (mEmptySearchBackground != null && mEmptySearchBackground.getAlpha() > 0) {
	c.clipRect(mBackgroundPadding.left, mBackgroundPadding.top,
	getWidth() - mBackgroundPadding.right,
	getHeight() - mBackgroundPadding.bottom);

	mEmptySearchBackground.draw(c);
	}

	super.onDraw(c);
	}

	@Override
	protected boolean verifyDrawable(Drawable who) {
	return who == mEmptySearchBackground \|\| super.verifyDrawable(who);
	}

	@Override
	protected void onSizeChanged(int w, int h, int oldw, int oldh) {
	updateEmptySearchBackgroundBounds();
	}

	@Override
	public void fillInLaunchSourceData(View v, Bundle sourceData) {
	sourceData.putString(Stats.SOURCE_EXTRA_CONTAINER, Stats.CONTAINER_ALL_APPS);
	if (mApps.hasFilter()) {
	sourceData.putString(Stats.SOURCE_EXTRA_SUB_CONTAINER,
	Stats.SUB_CONTAINER_ALL_APPS_SEARCH);
	} else {
	if (v instanceof BubbleTextView) {
	BubbleTextView icon = (BubbleTextView) v;
	int position = getChildPosition(icon);
	if (position != NO_POSITION) {
	List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
	AlphabeticalAppsList.AdapterItem item = items.get(position);
	if (item.viewType == AllAppsGridAdapter.PREDICTION_ICON_VIEW_TYPE) {
	sourceData.putString(Stats.SOURCE_EXTRA_SUB_CONTAINER,
	Stats.SUB_CONTAINER_ALL_APPS_PREDICTION);
	return;
	}
	}
	}
	sourceData.putString(Stats.SOURCE_EXTRA_SUB_CONTAINER,
	Stats.SUB_CONTAINER_ALL_APPS_A_Z);
	}
	}

	public void onSearchResultsChanged() {
	// Always scroll the view to the top so the user can see the changed results
	scrollToTop();

	if (mApps.hasNoFilteredResults()) {
	if (mEmptySearchBackground == null) {
	mEmptySearchBackground = new AllAppsBackgroundDrawable(getContext());
	mEmptySearchBackground.setAlpha(0);
	mEmptySearchBackground.setCallback(this);
	updateEmptySearchBackgroundBounds();
	}
	mEmptySearchBackground.animateBgAlpha(1f, 150);
	} else if (mEmptySearchBackground != null) {
	// For the time being, we just immediately hide the background to ensure that it does
	// not overlap with the results
	mEmptySearchBackground.setBgAlpha(0f);
	}
	}

	/**
	* Maps the touch (from 0..1) to the adapter position that should be visible.
	*/
	@Override
	public String scrollToPositionAtProgress(float touchFraction) {
	int rowCount = mApps.getNumAppRows();
	if (rowCount == 0) {
	return "";
	}

	// Stop the scroller if it is scrolling
	stopScroll();

	// Find the fastscroll section that maps to this touch fraction
	List<AlphabeticalAppsList.FastScrollSectionInfo> fastScrollSections =
	mApps.getFastScrollerSections();
	AlphabeticalAppsList.FastScrollSectionInfo lastInfo = fastScrollSections.get(0);
	for (int i = 1; i < fastScrollSections.size(); i++) {
	AlphabeticalAppsList.FastScrollSectionInfo info = fastScrollSections.get(i);
	if (info.touchFraction > touchFraction) {
	break;
	}
	lastInfo = info;
	}

	// Update the fast scroll
	int scrollY = getScrollTop(mScrollPosState);
	int availableScrollHeight = getAvailableScrollHeight(mApps.getNumAppRows());
	mFastScrollHelper.smoothScrollToSection(scrollY, availableScrollHeight, lastInfo);
	return lastInfo.sectionName;
	}

	@Override
	public void onFastScrollCompleted() {
	super.onFastScrollCompleted();
	mFastScrollHelper.onFastScrollCompleted();
	}

	@Override
	public void setAdapter(Adapter adapter) {
	super.setAdapter(adapter);
	mFastScrollHelper.onSetAdapter((AllAppsGridAdapter) adapter);
	}

	/**
	* Updates the bounds for the scrollbar.
	*/
	@Override
	public void onUpdateScrollbar(int dy) {
	List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();

	// Skip early if there are no items or we haven't been measured
	if (items.isEmpty() \|\| mNumAppsPerRow == 0) {
	mScrollbar.setThumbOffset(-1, -1);
	return;
	}

	// Find the index and height of the first visible row (all rows have the same height)
	int rowCount = mApps.getNumAppRows();
	getCurScrollState(mScrollPosState, -1);
	if (mScrollPosState.rowIndex < 0) {
	mScrollbar.setThumbOffset(-1, -1);
	return;
	}

	// Only show the scrollbar if there is height to be scrolled
	int availableScrollBarHeight = getAvailableScrollBarHeight();
	int availableScrollHeight = getAvailableScrollHeight(mApps.getNumAppRows());
	if (availableScrollHeight <= 0) {
	mScrollbar.setThumbOffset(-1, -1);
	return;
	}

	// Calculate the current scroll position, the scrollY of the recycler view accounts for the
	// view padding, while the scrollBarY is drawn right up to the background padding (ignoring
	// padding)
	int scrollY = getScrollTop(mScrollPosState);
	int scrollBarY = mBackgroundPadding.top +
	(int) (((float) scrollY / availableScrollHeight) * availableScrollBarHeight);

	if (mScrollbar.isThumbDetached()) {
	int scrollBarX;
	if (Utilities.isRtl(getResources())) {
	scrollBarX = mBackgroundPadding.left;
	} else {
	scrollBarX = getWidth() - mBackgroundPadding.right - mScrollbar.getThumbWidth();
	}

	if (mScrollbar.isDraggingThumb()) {
	// If the thumb is detached, then just update the thumb to the current
	// touch position
	mScrollbar.setThumbOffset(scrollBarX, (int) mScrollbar.getLastTouchY());
	} else {
	int thumbScrollY = mScrollbar.getThumbOffset().y;
	int diffScrollY = scrollBarY - thumbScrollY;
	if (diffScrollY * dy > 0f) {
	// User is scrolling in the same direction the thumb needs to catch up to the
	// current scroll position. We do this by mapping the difference in movement
	// from the original scroll bar position to the difference in movement necessary
	// in the detached thumb position to ensure that both speed towards the same
	// position at either end of the list.
	if (dy < 0) {
	int offset = (int) ((dy * thumbScrollY) / (float) scrollBarY);
	thumbScrollY += Math.max(offset, diffScrollY);
	} else {
	int offset = (int) ((dy * (availableScrollBarHeight - thumbScrollY)) /
	(float) (availableScrollBarHeight - scrollBarY));
	thumbScrollY += Math.min(offset, diffScrollY);
	}
	thumbScrollY = Math.max(0, Math.min(availableScrollBarHeight, thumbScrollY));
	mScrollbar.setThumbOffset(scrollBarX, thumbScrollY);
	if (scrollBarY == thumbScrollY) {
	mScrollbar.reattachThumbToScroll();
	}
	} else {
	// User is scrolling in an opposite direction to the direction that the thumb
	// needs to catch up to the scroll position. Do nothing except for updating
	// the scroll bar x to match the thumb width.
	mScrollbar.setThumbOffset(scrollBarX, thumbScrollY);
	}
	}
	} else {
	synchronizeScrollBarThumbOffsetToViewScroll(mScrollPosState, rowCount);
	}
	}

	/**
	* Returns the current scroll state of the apps rows.
	*/
	protected void getCurScrollState(ScrollPositionState stateOut, int viewTypeMask) {
	stateOut.rowIndex = -1;
	stateOut.rowTopOffset = -1;
	stateOut.itemPos = -1;

	// Return early if there are no items or we haven't been measured
	List<AlphabeticalAppsList.AdapterItem> items = mApps.getAdapterItems();
	if (items.isEmpty() \|\| mNumAppsPerRow == 0) {
	return;
	}

	int childCount = getChildCount();
	for (int i = 0; i < childCount; i++) {
	View child = getChildAt(i);
	int position = getChildPosition(child);
	if (position != NO_POSITION) {
	AlphabeticalAppsList.AdapterItem item = items.get(position);
	if ((item.viewType & viewTypeMask) != 0) {
	stateOut.rowIndex = item.rowIndex;
	stateOut.rowTopOffset = getLayoutManager().getDecoratedTop(child);
	stateOut.itemPos = position;
	return;
	}
	}
	}
	return;
	}

	@Override
	protected boolean supportsFastScrolling() {
	// Only allow fast scrolling when the user is not searching, since the results are not
	// grouped in a meaningful order
	return !mApps.hasFilter();
	}

	protected int getTop(int rowIndex) {
	if (getChildCount() == 0 \|\| rowIndex <= 0) {
	return 0;
	}

	// The prediction bar icons have more padding, so account for that in the row offset
	return mPredictionIconHeight + (rowIndex - 1) * mIconHeight;
	}

	/**
	* Updates the bounds of the empty search background.
	*/
	private void updateEmptySearchBackgroundBounds() {
	if (mEmptySearchBackground == null) {
	return;
	}

	// Center the empty search background on this new view bounds
	int x = (getMeasuredWidth() - mEmptySearchBackground.getIntrinsicWidth()) / 2;
	int y = mEmptySearchBackgroundTopOffset;
	mEmptySearchBackground.setBounds(x, y,
	x + mEmptySearchBackground.getIntrinsicWidth(),
	y + mEmptySearchBackground.getIntrinsicHeight());
	}
	}