android-34/com/android/systemui/accessibility/accessibilitymenu/view/A11yMenuViewPager.java - platform/prebuilts/fullsdk/sources - Git at Google

 /*
  * Copyright (C) 2023 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.systemui.accessibility.accessibilitymenu.view;

 import android.content.Context;
 import android.content.res.Configuration;
 import android.graphics.Insets;
 import android.util.DisplayMetrics;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewTreeObserver.OnGlobalLayoutListener;
 import android.view.WindowInsets;
 import android.view.WindowManager;
 import android.view.WindowMetrics;
 import android.widget.GridView;

 import androidx.viewpager.widget.ViewPager;

 import com.android.systemui.accessibility.accessibilitymenu.AccessibilityMenuService;
 import com.android.systemui.accessibility.accessibilitymenu.R;
 import com.android.systemui.accessibility.accessibilitymenu.activity.A11yMenuSettingsActivity.A11yMenuPreferenceFragment;
 import com.android.systemui.accessibility.accessibilitymenu.model.A11yMenuShortcut;
 import com.android.systemui.accessibility.accessibilitymenu.view.A11yMenuFooter.A11yMenuFooterCallBack;

 import java.util.ArrayList;
 import java.util.List;

 /**
  * This class handles UI for viewPager and footer.
  * It displays grid pages containing all shortcuts in viewPager,
  * and handles the click events from footer to switch between pages.
  */
 public class A11yMenuViewPager {

     /** The default index of the ViewPager. */
     public static final int DEFAULT_PAGE_INDEX = 0;

     /**
      * The class holds the static parameters for grid view when large button settings is on/off.
      */
     public static final class GridViewParams {
         /** Total shortcuts count in the grid view when large button settings is off. */
         public static final int GRID_ITEM_COUNT = 9;

         /** The number of columns in the grid view when large button settings is off. */
         public static final int GRID_COLUMN_COUNT = 3;

         /** Total shortcuts count in the grid view when large button settings is on. */
         public static final int LARGE_GRID_ITEM_COUNT = 4;

         /** The number of columns in the grid view when large button settings is on. */
         public static final int LARGE_GRID_COLUMN_COUNT = 2;

         /**
          * Returns the number of items in the grid view.
          *
          * @param context The parent context
          * @return Grid item count
          */
         public static int getGridItemCount(Context context) {
             return A11yMenuPreferenceFragment.isLargeButtonsEnabled(context)
                    ? LARGE_GRID_ITEM_COUNT
                    : GRID_ITEM_COUNT;
         }

         /**
          * Returns the number of columns in the grid view.
          *
          * @param context The parent context
          * @return Grid column count
          */
         public static int getGridColumnCount(Context context) {
             return A11yMenuPreferenceFragment.isLargeButtonsEnabled(context)
                    ? LARGE_GRID_COLUMN_COUNT
                    : GRID_COLUMN_COUNT;
         }

         /**
          * Returns the number of rows in the grid view.
          *
          * @param context The parent context
          * @return Grid row count
          */
         public static int getGridRowCount(Context context) {
             return A11yMenuPreferenceFragment.isLargeButtonsEnabled(context)
                    ? (LARGE_GRID_ITEM_COUNT / LARGE_GRID_COLUMN_COUNT)
                    : (GRID_ITEM_COUNT / GRID_COLUMN_COUNT);
         }

         /**
          * Separates a provided list of accessibility shortcuts into multiple sub-lists.
          * Does not modify the original list.
          *
          * @param pageItemCount The maximum size of an individual sub-list.
          * @param shortcutList The list of shortcuts to be separated into sub-lists.
          * @return A list of shortcut sub-lists.
          */
         public static List<List<A11yMenuShortcut>> generateShortcutSubLists(
                 int pageItemCount, List<A11yMenuShortcut> shortcutList) {
             int start = 0;
             int end;
             int shortcutListSize = shortcutList.size();
             List<List<A11yMenuShortcut>> subLists = new ArrayList<>();
             while (start < shortcutListSize) {
                 end = Math.min(start + pageItemCount, shortcutListSize);
                 subLists.add(shortcutList.subList(start, end));
                 start = end;
             }
             return subLists;
         }

         private GridViewParams() {}
     }

     private final AccessibilityMenuService mService;

     /**
      * The pager widget, which handles animation and allows swiping horizontally to access previous
      * and next gridView pages.
      */
     protected ViewPager mViewPager;

     private ViewPagerAdapter<GridView> mViewPagerAdapter;
     private final List<GridView> mGridPageList = new ArrayList<>();

     /** The footer, which provides buttons to switch between pages */
     protected A11yMenuFooter mA11yMenuFooter;

     /** The shortcut list intended to show in grid pages of viewPager */
     private List<A11yMenuShortcut> mA11yMenuShortcutList;

     /** The container layout for a11y menu. */
     private ViewGroup mA11yMenuLayout;

     public A11yMenuViewPager(AccessibilityMenuService service) {
         this.mService = service;
     }

     /**
      * Configures UI for view pager and footer.
      *
      * @param a11yMenuLayout the container layout for a11y menu
      * @param shortcutDataList the data list need to show in view pager
      * @param pageIndex the index of ViewPager to show
      */
     public void configureViewPagerAndFooter(
             ViewGroup a11yMenuLayout, List<A11yMenuShortcut> shortcutDataList, int pageIndex) {
         this.mA11yMenuLayout = a11yMenuLayout;
         mA11yMenuShortcutList = shortcutDataList;
         initViewPager();
         initChildPage();
         mA11yMenuFooter = new A11yMenuFooter(a11yMenuLayout, mFooterCallbacks);
         updateFooterState();
         registerOnGlobalLayoutListener();
         goToPage(pageIndex);
     }

     /** Initializes viewPager and its adapter. */
     private void initViewPager() {
         mViewPager = mA11yMenuLayout.findViewById(R.id.view_pager);
         mViewPagerAdapter = new ViewPagerAdapter<>();
         mViewPager.setAdapter(mViewPagerAdapter);
         mViewPager.setOverScrollMode(View.OVER_SCROLL_NEVER);
         mViewPager.addOnPageChangeListener(
                 new ViewPager.OnPageChangeListener() {
                     @Override
                     public void onPageScrollStateChanged(int state) {}

                     @Override
                     public void onPageScrolled(
                             int position, float positionOffset, int positionOffsetPixels) {}

                     @Override
                     public void onPageSelected(int position) {
                         updateFooterState();
                     }
                 });
     }

     /** Creates child pages of viewPager by the length of shortcuts and initializes them. */
     private void initChildPage() {
         if (mA11yMenuShortcutList == null || mA11yMenuShortcutList.isEmpty()) {
             return;
         }

         if (!mGridPageList.isEmpty()) {
             mGridPageList.clear();
         }

         // Generate pages by calculating # of items per grid.
         for (List<A11yMenuShortcut> page : GridViewParams.generateShortcutSubLists(
                 GridViewParams.getGridItemCount(mService), mA11yMenuShortcutList)
         ) {
             addGridPage(page);
         }

         mViewPagerAdapter.set(mGridPageList);
     }

     private void addGridPage(List<A11yMenuShortcut> shortcutDataListInPage) {
         LayoutInflater inflater = LayoutInflater.from(mService);
         View view = inflater.inflate(R.layout.grid_view, null);
         GridView gridView = view.findViewById(R.id.gridview);
         A11yMenuAdapter adapter = new A11yMenuAdapter(mService, shortcutDataListInPage);
         gridView.setNumColumns(GridViewParams.getGridColumnCount(mService));
         gridView.setAdapter(adapter);
         mGridPageList.add(gridView);
     }

     /** Updates footer's state by index of current page in view pager. */
     private void updateFooterState() {
         int currentPage = mViewPager.getCurrentItem();
         int lastPage = mViewPager.getAdapter().getCount() - 1;
         mA11yMenuFooter.getPreviousPageBtn().setEnabled(currentPage > 0);
         mA11yMenuFooter.getNextPageBtn().setEnabled(currentPage < lastPage);
     }

     private void goToPage(int pageIndex) {
         if (mViewPager == null) {
             return;
         }
         if ((pageIndex >= 0) && (pageIndex < mViewPager.getAdapter().getCount())) {
             mViewPager.setCurrentItem(pageIndex);
         }
     }

     /** Registers OnGlobalLayoutListener to adjust menu UI by running callback at first time. */
     private void registerOnGlobalLayoutListener() {
         mA11yMenuLayout
                 .getViewTreeObserver()
                 .addOnGlobalLayoutListener(
                         new OnGlobalLayoutListener() {

                             boolean mIsFirstTime = true;

                             @Override
                             public void onGlobalLayout() {
                                 if (!mIsFirstTime) {
                                     return;
                                 }

                                 if (mGridPageList.isEmpty()) {
                                     return;
                                 }

                                 GridView firstGridView = mGridPageList.get(0);
                                 if (firstGridView == null
                                         || firstGridView.getChildAt(0) == null) {
                                     return;
                                 }

                                 mIsFirstTime = false;

                                 int gridItemHeight = firstGridView.getChildAt(0)
                                                 .getMeasuredHeight();
                                 adjustMenuUISize(gridItemHeight);
                             }
                         });
     }

     /**
      * Adjusts menu UI to fit both landscape and portrait mode.
      *
      * <ol>
      *   <li>Adjust view pager's height.
      *   <li>Adjust vertical interval between grid items.
      *   <li>Adjust padding in view pager.
      * </ol>
      */
     private void adjustMenuUISize(int gridItemHeight) {
         final int rowsInGridView = GridViewParams.getGridRowCount(mService);
         final int defaultMargin =
                 (int) mService.getResources().getDimension(R.dimen.a11ymenu_layout_margin);
         final int topMargin = (int) mService.getResources().getDimension(R.dimen.table_margin_top);
         final int displayMode = mService.getResources().getConfiguration().orientation;
         int viewPagerHeight = mViewPager.getMeasuredHeight();

         if (displayMode == Configuration.ORIENTATION_PORTRAIT) {
             // In portrait mode, we only need to adjust view pager's height to match its
             // child's height.
             viewPagerHeight = gridItemHeight * rowsInGridView + defaultMargin + topMargin;
         } else if (displayMode == Configuration.ORIENTATION_LANDSCAPE) {
             // In landscape mode, we need to adjust view pager's height to match screen height
             // and adjust its child too,
             // because a11y menu layout height is limited by the screen height.
             DisplayMetrics displayMetrics = mService.getResources().getDisplayMetrics();
             float densityScale = (float) displayMetrics.densityDpi
                     / DisplayMetrics.DENSITY_DEVICE_STABLE;
             View footerLayout = mA11yMenuLayout.findViewById(R.id.footerlayout);
             // Keeps footer window height unchanged no matter the density is changed.
             footerLayout.getLayoutParams().height =
                     (int) (footerLayout.getLayoutParams().height / densityScale);
             // Adjust the view pager height for system bar and display cutout insets.
             WindowManager windowManager = mService.getSystemService(WindowManager.class);
             WindowMetrics windowMetric = windowManager.getCurrentWindowMetrics();
             Insets windowInsets = windowMetric.getWindowInsets().getInsetsIgnoringVisibility(
                     WindowInsets.Type.systemBars() | WindowInsets.Type.displayCutout());
             viewPagerHeight =
                     windowMetric.getBounds().height()
                             - footerLayout.getLayoutParams().height
                             - windowInsets.bottom;
             // Sets vertical interval between grid items.
             int interval =
                     (viewPagerHeight - topMargin - defaultMargin
                             - (rowsInGridView * gridItemHeight))
                             / (rowsInGridView + 1);
             for (GridView gridView : mGridPageList) {
                 gridView.setVerticalSpacing(interval);
             }

             // Sets padding to view pager.
             final int finalMarginTop = interval + topMargin;
             mViewPager.setPadding(defaultMargin, finalMarginTop, defaultMargin, defaultMargin);
         }
         final ViewGroup.LayoutParams layoutParams = mViewPager.getLayoutParams();
         layoutParams.height = viewPagerHeight;
         mViewPager.setLayoutParams(layoutParams);
     }

     /** Callback object to handle click events from A11yMenuFooter */
     protected A11yMenuFooterCallBack mFooterCallbacks =
             new A11yMenuFooterCallBack() {
                 @Override
                 public void onLeftButtonClicked() {
                     // Moves to previous page.
                     int targetPage = mViewPager.getCurrentItem() - 1;
                     goToPage(targetPage);
                     updateFooterState();
                 }

                 @Override
                 public void onRightButtonClicked() {
                     // Moves to next page.
                     int targetPage = mViewPager.getCurrentItem() + 1;
                     goToPage(targetPage);
                     updateFooterState();
                 }
             };
 }
	/*
	* Copyright (C) 2023 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.systemui.accessibility.accessibilitymenu.view;

	import android.content.Context;
	import android.content.res.Configuration;
	import android.graphics.Insets;
	import android.util.DisplayMetrics;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.view.ViewTreeObserver.OnGlobalLayoutListener;
	import android.view.WindowInsets;
	import android.view.WindowManager;
	import android.view.WindowMetrics;
	import android.widget.GridView;

	import androidx.viewpager.widget.ViewPager;

	import com.android.systemui.accessibility.accessibilitymenu.AccessibilityMenuService;
	import com.android.systemui.accessibility.accessibilitymenu.R;
	import com.android.systemui.accessibility.accessibilitymenu.activity.A11yMenuSettingsActivity.A11yMenuPreferenceFragment;
	import com.android.systemui.accessibility.accessibilitymenu.model.A11yMenuShortcut;
	import com.android.systemui.accessibility.accessibilitymenu.view.A11yMenuFooter.A11yMenuFooterCallBack;

	import java.util.ArrayList;
	import java.util.List;

	/**
	* This class handles UI for viewPager and footer.
	* It displays grid pages containing all shortcuts in viewPager,
	* and handles the click events from footer to switch between pages.
	*/
	public class A11yMenuViewPager {

	/** The default index of the ViewPager. */
	public static final int DEFAULT_PAGE_INDEX = 0;

	/**
	* The class holds the static parameters for grid view when large button settings is on/off.
	*/
	public static final class GridViewParams {
	/** Total shortcuts count in the grid view when large button settings is off. */
	public static final int GRID_ITEM_COUNT = 9;

	/** The number of columns in the grid view when large button settings is off. */
	public static final int GRID_COLUMN_COUNT = 3;

	/** Total shortcuts count in the grid view when large button settings is on. */
	public static final int LARGE_GRID_ITEM_COUNT = 4;

	/** The number of columns in the grid view when large button settings is on. */
	public static final int LARGE_GRID_COLUMN_COUNT = 2;

	/**
	* Returns the number of items in the grid view.
	*
	* @param context The parent context
	* @return Grid item count
	*/
	public static int getGridItemCount(Context context) {
	return A11yMenuPreferenceFragment.isLargeButtonsEnabled(context)
	? LARGE_GRID_ITEM_COUNT
	: GRID_ITEM_COUNT;
	}

	/**
	* Returns the number of columns in the grid view.
	*
	* @param context The parent context
	* @return Grid column count
	*/
	public static int getGridColumnCount(Context context) {
	return A11yMenuPreferenceFragment.isLargeButtonsEnabled(context)
	? LARGE_GRID_COLUMN_COUNT
	: GRID_COLUMN_COUNT;
	}

	/**
	* Returns the number of rows in the grid view.
	*
	* @param context The parent context
	* @return Grid row count
	*/
	public static int getGridRowCount(Context context) {
	return A11yMenuPreferenceFragment.isLargeButtonsEnabled(context)
	? (LARGE_GRID_ITEM_COUNT / LARGE_GRID_COLUMN_COUNT)
	: (GRID_ITEM_COUNT / GRID_COLUMN_COUNT);
	}

	/**
	* Separates a provided list of accessibility shortcuts into multiple sub-lists.
	* Does not modify the original list.
	*
	* @param pageItemCount The maximum size of an individual sub-list.
	* @param shortcutList The list of shortcuts to be separated into sub-lists.
	* @return A list of shortcut sub-lists.
	*/
	public static List<List<A11yMenuShortcut>> generateShortcutSubLists(
	int pageItemCount, List<A11yMenuShortcut> shortcutList) {
	int start = 0;
	int end;
	int shortcutListSize = shortcutList.size();
	List<List<A11yMenuShortcut>> subLists = new ArrayList<>();
	while (start < shortcutListSize) {
	end = Math.min(start + pageItemCount, shortcutListSize);
	subLists.add(shortcutList.subList(start, end));
	start = end;
	}
	return subLists;
	}

	private GridViewParams() {}
	}

	private final AccessibilityMenuService mService;

	/**
	* The pager widget, which handles animation and allows swiping horizontally to access previous
	* and next gridView pages.
	*/
	protected ViewPager mViewPager;

	private ViewPagerAdapter<GridView> mViewPagerAdapter;
	private final List<GridView> mGridPageList = new ArrayList<>();

	/** The footer, which provides buttons to switch between pages */
	protected A11yMenuFooter mA11yMenuFooter;

	/** The shortcut list intended to show in grid pages of viewPager */
	private List<A11yMenuShortcut> mA11yMenuShortcutList;

	/** The container layout for a11y menu. */
	private ViewGroup mA11yMenuLayout;

	public A11yMenuViewPager(AccessibilityMenuService service) {
	this.mService = service;
	}

	/**
	* Configures UI for view pager and footer.
	*
	* @param a11yMenuLayout the container layout for a11y menu
	* @param shortcutDataList the data list need to show in view pager
	* @param pageIndex the index of ViewPager to show
	*/
	public void configureViewPagerAndFooter(
	ViewGroup a11yMenuLayout, List<A11yMenuShortcut> shortcutDataList, int pageIndex) {
	this.mA11yMenuLayout = a11yMenuLayout;
	mA11yMenuShortcutList = shortcutDataList;
	initViewPager();
	initChildPage();
	mA11yMenuFooter = new A11yMenuFooter(a11yMenuLayout, mFooterCallbacks);
	updateFooterState();
	registerOnGlobalLayoutListener();
	goToPage(pageIndex);
	}

	/** Initializes viewPager and its adapter. */
	private void initViewPager() {
	mViewPager = mA11yMenuLayout.findViewById(R.id.view_pager);
	mViewPagerAdapter = new ViewPagerAdapter<>();
	mViewPager.setAdapter(mViewPagerAdapter);
	mViewPager.setOverScrollMode(View.OVER_SCROLL_NEVER);
	mViewPager.addOnPageChangeListener(
	new ViewPager.OnPageChangeListener() {
	@Override
	public void onPageScrollStateChanged(int state) {}

	@Override
	public void onPageScrolled(
	int position, float positionOffset, int positionOffsetPixels) {}

	@Override
	public void onPageSelected(int position) {
	updateFooterState();
	}
	});
	}

	/** Creates child pages of viewPager by the length of shortcuts and initializes them. */
	private void initChildPage() {
	if (mA11yMenuShortcutList == null \|\| mA11yMenuShortcutList.isEmpty()) {
	return;
	}

	if (!mGridPageList.isEmpty()) {
	mGridPageList.clear();
	}

	// Generate pages by calculating # of items per grid.
	for (List<A11yMenuShortcut> page : GridViewParams.generateShortcutSubLists(
	GridViewParams.getGridItemCount(mService), mA11yMenuShortcutList)
	) {
	addGridPage(page);
	}

	mViewPagerAdapter.set(mGridPageList);
	}

	private void addGridPage(List<A11yMenuShortcut> shortcutDataListInPage) {
	LayoutInflater inflater = LayoutInflater.from(mService);
	View view = inflater.inflate(R.layout.grid_view, null);
	GridView gridView = view.findViewById(R.id.gridview);
	A11yMenuAdapter adapter = new A11yMenuAdapter(mService, shortcutDataListInPage);
	gridView.setNumColumns(GridViewParams.getGridColumnCount(mService));
	gridView.setAdapter(adapter);
	mGridPageList.add(gridView);
	}

	/** Updates footer's state by index of current page in view pager. */
	private void updateFooterState() {
	int currentPage = mViewPager.getCurrentItem();
	int lastPage = mViewPager.getAdapter().getCount() - 1;
	mA11yMenuFooter.getPreviousPageBtn().setEnabled(currentPage > 0);
	mA11yMenuFooter.getNextPageBtn().setEnabled(currentPage < lastPage);
	}

	private void goToPage(int pageIndex) {
	if (mViewPager == null) {
	return;
	}
	if ((pageIndex >= 0) && (pageIndex < mViewPager.getAdapter().getCount())) {
	mViewPager.setCurrentItem(pageIndex);
	}
	}

	/** Registers OnGlobalLayoutListener to adjust menu UI by running callback at first time. */
	private void registerOnGlobalLayoutListener() {
	mA11yMenuLayout
	.getViewTreeObserver()
	.addOnGlobalLayoutListener(
	new OnGlobalLayoutListener() {

	boolean mIsFirstTime = true;

	@Override
	public void onGlobalLayout() {
	if (!mIsFirstTime) {
	return;
	}

	if (mGridPageList.isEmpty()) {
	return;
	}

	GridView firstGridView = mGridPageList.get(0);
	if (firstGridView == null
	\|\| firstGridView.getChildAt(0) == null) {
	return;
	}

	mIsFirstTime = false;

	int gridItemHeight = firstGridView.getChildAt(0)
	.getMeasuredHeight();
	adjustMenuUISize(gridItemHeight);
	}
	});
	}

	/**
	* Adjusts menu UI to fit both landscape and portrait mode.
	*
	* <ol>
	* <li>Adjust view pager's height.
	* <li>Adjust vertical interval between grid items.
	* <li>Adjust padding in view pager.
	* </ol>
	*/
	private void adjustMenuUISize(int gridItemHeight) {
	final int rowsInGridView = GridViewParams.getGridRowCount(mService);
	final int defaultMargin =
	(int) mService.getResources().getDimension(R.dimen.a11ymenu_layout_margin);
	final int topMargin = (int) mService.getResources().getDimension(R.dimen.table_margin_top);
	final int displayMode = mService.getResources().getConfiguration().orientation;
	int viewPagerHeight = mViewPager.getMeasuredHeight();

	if (displayMode == Configuration.ORIENTATION_PORTRAIT) {
	// In portrait mode, we only need to adjust view pager's height to match its
	// child's height.
	viewPagerHeight = gridItemHeight * rowsInGridView + defaultMargin + topMargin;
	} else if (displayMode == Configuration.ORIENTATION_LANDSCAPE) {
	// In landscape mode, we need to adjust view pager's height to match screen height
	// and adjust its child too,
	// because a11y menu layout height is limited by the screen height.
	DisplayMetrics displayMetrics = mService.getResources().getDisplayMetrics();
	float densityScale = (float) displayMetrics.densityDpi
	/ DisplayMetrics.DENSITY_DEVICE_STABLE;
	View footerLayout = mA11yMenuLayout.findViewById(R.id.footerlayout);
	// Keeps footer window height unchanged no matter the density is changed.
	footerLayout.getLayoutParams().height =
	(int) (footerLayout.getLayoutParams().height / densityScale);
	// Adjust the view pager height for system bar and display cutout insets.
	WindowManager windowManager = mService.getSystemService(WindowManager.class);
	WindowMetrics windowMetric = windowManager.getCurrentWindowMetrics();
	Insets windowInsets = windowMetric.getWindowInsets().getInsetsIgnoringVisibility(
	WindowInsets.Type.systemBars() \| WindowInsets.Type.displayCutout());
	viewPagerHeight =
	windowMetric.getBounds().height()
	- footerLayout.getLayoutParams().height
	- windowInsets.bottom;
	// Sets vertical interval between grid items.
	int interval =
	(viewPagerHeight - topMargin - defaultMargin
	- (rowsInGridView * gridItemHeight))
	/ (rowsInGridView + 1);
	for (GridView gridView : mGridPageList) {
	gridView.setVerticalSpacing(interval);
	}

	// Sets padding to view pager.
	final int finalMarginTop = interval + topMargin;
	mViewPager.setPadding(defaultMargin, finalMarginTop, defaultMargin, defaultMargin);
	}
	final ViewGroup.LayoutParams layoutParams = mViewPager.getLayoutParams();
	layoutParams.height = viewPagerHeight;
	mViewPager.setLayoutParams(layoutParams);
	}

	/** Callback object to handle click events from A11yMenuFooter */
	protected A11yMenuFooterCallBack mFooterCallbacks =
	new A11yMenuFooterCallBack() {
	@Override
	public void onLeftButtonClicked() {
	// Moves to previous page.
	int targetPage = mViewPager.getCurrentItem() - 1;
	goToPage(targetPage);
	updateFooterState();
	}

	@Override
	public void onRightButtonClicked() {
	// Moves to next page.
	int targetPage = mViewPager.getCurrentItem() + 1;
	goToPage(targetPage);
	updateFooterState();
	}
	};
	}