src/com/android/settings/AccessibilitySettings.java - LeafOS-Project/android_packages_apps_Settings - Gitiles

 /*
  * Copyright (C) 2009 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.settings;

 import android.app.AlertDialog;
 import android.app.Service;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.pm.ServiceInfo;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.SystemProperties;
 import android.preference.CheckBoxPreference;
 import android.preference.Preference;
 import android.preference.PreferenceActivity;
 import android.preference.PreferenceCategory;
 import android.preference.PreferenceGroup;
 import android.preference.PreferenceScreen;
 import android.provider.Settings;
 import android.text.TextUtils;
 import android.view.KeyCharacterMap;
 import android.view.KeyEvent;
 import android.view.accessibility.AccessibilityManager;

 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;

 /**
  * Activity with the accessibility settings.
  */
 public class AccessibilitySettings extends PreferenceActivity {
     private static final String DEFAULT_SCREENREADER_MARKET_LINK =
         "market://search?q=pname:com.google.android.marvin.talkback";

     private final String TOGGLE_ACCESSIBILITY_SERVICE_CHECKBOX =
         "toggle_accessibility_service_checkbox";

     private static final String ACCESSIBILITY_SERVICES_CATEGORY =
         "accessibility_services_category";

     private static final String POWER_BUTTON_CATEGORY =
         "power_button_category";

     private final String POWER_BUTTON_ENDS_CALL_CHECKBOX =
         "power_button_ends_call";

     private CheckBoxPreference mToggleCheckBox;

     private PreferenceCategory mPowerButtonCategory;
     private CheckBoxPreference mPowerButtonEndsCallCheckBox;

     private Map<String, ServiceInfo> mAccessibilityServices =
         new LinkedHashMap<String, ServiceInfo>();

     private TextUtils.SimpleStringSplitter mStringColonSplitter =
         new TextUtils.SimpleStringSplitter(':');

     private PreferenceGroup mAccessibilityServicesCategory;

     @Override
     protected void onCreate(Bundle icicle) {
         super.onCreate(icicle);
         addPreferencesFromResource(R.xml.accessibility_settings);

         mToggleCheckBox = (CheckBoxPreference) findPreference(
             TOGGLE_ACCESSIBILITY_SERVICE_CHECKBOX);

         mPowerButtonCategory = (PreferenceCategory) findPreference(POWER_BUTTON_CATEGORY);
         mPowerButtonEndsCallCheckBox = (CheckBoxPreference) findPreference(
             POWER_BUTTON_ENDS_CALL_CHECKBOX);

         addAccessibilitServicePreferences();
     }

     @Override
     protected void onResume() {
         super.onResume();

         final HashSet<String> enabled = new HashSet<String>();
         String settingValue = Settings.Secure.getString(getContentResolver(),
                 Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES);
         if (settingValue != null) {
             TextUtils.SimpleStringSplitter splitter = mStringColonSplitter;
             splitter.setString(settingValue);
             while (splitter.hasNext()) {
                 enabled.add(splitter.next());
             }
         }

         Map<String, ServiceInfo> accessibilityServices = mAccessibilityServices;

         for (String key : accessibilityServices.keySet()) {
             CheckBoxPreference preference = (CheckBoxPreference) findPreference(key);
             if (preference != null) {
                 preference.setChecked(enabled.contains(key));
             }
         }

         int serviceState = Settings.Secure.getInt(getContentResolver(),
             Settings.Secure.ACCESSIBILITY_ENABLED, 0);

         if (!accessibilityServices.isEmpty()) {
             if (serviceState == 1) {
                 mToggleCheckBox.setChecked(true);
             } else {
                 setAccessibilityServicePreferencesState(false);
             }
             mToggleCheckBox.setEnabled(true);
         } else {
             if (serviceState == 1) {
                 // no service and accessibility is enabled => disable
                 Settings.Secure.putInt(getContentResolver(),
                     Settings.Secure.ACCESSIBILITY_ENABLED, 0);
             }
             mToggleCheckBox.setEnabled(false);
             // Notify user that they do not have any accessibility apps
             // installed and direct them to Market to get TalkBack
             displayNoAppsAlert();
         }

         if (KeyCharacterMap.deviceHasKey(KeyEvent.KEYCODE_POWER)) {
             int incallPowerBehavior = Settings.Secure.getInt(getContentResolver(),
                     Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR,
                     Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_DEFAULT);
             // The checkbox is labeled "Power button ends call"; thus the in-call
             // Power button behavior is INCALL_POWER_BUTTON_BEHAVIOR_HANGUP if
             // checked, and INCALL_POWER_BUTTON_BEHAVIOR_SCREEN_OFF if unchecked.
             boolean powerButtonCheckboxEnabled =
                     (incallPowerBehavior == Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP);
             mPowerButtonEndsCallCheckBox.setChecked(powerButtonCheckboxEnabled);
             mPowerButtonEndsCallCheckBox.setEnabled(true);
         } else {
             // No POWER key on the current device; this entire category is irrelevant.
             getPreferenceScreen().removePreference(mPowerButtonCategory);
         }
     }

     @Override
     protected void onPause() {
         super.onPause();

         persistEnabledAccessibilityServices();
     }

     /**
      * Sets the state of the preferences for enabling/disabling
      * AccessibilityServices.
      *
      * @param isEnabled If to enable or disable the preferences.
      */
     private void setAccessibilityServicePreferencesState(boolean isEnabled) {
         if (mAccessibilityServicesCategory == null) {
             return;
         }

         int count = mAccessibilityServicesCategory.getPreferenceCount();
         for (int i = 0; i < count; i++) {
             Preference pref = mAccessibilityServicesCategory.getPreference(i);
             pref.setEnabled(isEnabled);
         }
     }

     @Override
     public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
         final String key = preference.getKey();

         if (TOGGLE_ACCESSIBILITY_SERVICE_CHECKBOX.equals(key)) {
             boolean isChecked = ((CheckBoxPreference) preference).isChecked();
             handleEnableAccessibilityStateChange((CheckBoxPreference) preference);
         } else if (POWER_BUTTON_ENDS_CALL_CHECKBOX.equals(key)) {
             boolean isChecked = ((CheckBoxPreference) preference).isChecked();
             // The checkbox is labeled "Power button ends call"; thus the in-call
             // Power button behavior is INCALL_POWER_BUTTON_BEHAVIOR_HANGUP if
             // checked, and INCALL_POWER_BUTTON_BEHAVIOR_SCREEN_OFF if unchecked.
             Settings.Secure.putInt(getContentResolver(),
                     Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR,
                     (isChecked ? Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP
                             : Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_SCREEN_OFF));
         } else if (preference instanceof CheckBoxPreference) {
             handleEnableAccessibilityServiceStateChange((CheckBoxPreference) preference);
         }

         return super.onPreferenceTreeClick(preferenceScreen, preference);
     }

     /**
      * Handles the change of the accessibility enabled setting state.
      *
      * @param preference The preference for enabling/disabling accessibility.
      */
     private void handleEnableAccessibilityStateChange(CheckBoxPreference preference) {
         if (preference.isChecked()) {
             Settings.Secure.putInt(getContentResolver(),
                 Settings.Secure.ACCESSIBILITY_ENABLED, 1);
             setAccessibilityServicePreferencesState(true);
         } else {
             final CheckBoxPreference checkBoxPreference = preference;
             AlertDialog dialog = (new AlertDialog.Builder(this))
                 .setTitle(android.R.string.dialog_alert_title)
                 .setIcon(android.R.drawable.ic_dialog_alert)
                 .setMessage(getString(R.string.accessibility_service_disable_warning))
                 .setCancelable(true)
                 .setPositiveButton(android.R.string.ok,
                     new DialogInterface.OnClickListener() {
                         public void onClick(DialogInterface dialog, int which) {
                             Settings.Secure.putInt(getContentResolver(),
                                 Settings.Secure.ACCESSIBILITY_ENABLED, 0);
                             setAccessibilityServicePreferencesState(false);
                         }
                 })
                 .setNegativeButton(android.R.string.cancel,
                     new DialogInterface.OnClickListener() {
                         public void onClick(DialogInterface dialog, int which) {
                             checkBoxPreference.setChecked(true);
                         }
                 })
                 .create();
             dialog.show();
         }
     }

     /**
      * Handles the change of the preference for enabling/disabling an AccessibilityService.
      *
      * @param preference The preference.
      */
     private void handleEnableAccessibilityServiceStateChange(CheckBoxPreference preference) {
         if (preference.isChecked()) {
             final CheckBoxPreference checkBoxPreference = preference;
             AlertDialog dialog = (new AlertDialog.Builder(this))
                 .setTitle(android.R.string.dialog_alert_title)
                 .setIcon(android.R.drawable.ic_dialog_alert)
                 .setMessage(getString(R.string.accessibility_service_security_warning,
                     mAccessibilityServices.get(preference.getKey())
                     .applicationInfo.loadLabel(getPackageManager())))
                 .setCancelable(true)
                 .setPositiveButton(android.R.string.ok,
                         new DialogInterface.OnClickListener() {
                             public void onClick(DialogInterface dialog, int which) {
                                 checkBoxPreference.setChecked(true);
                                 persistEnabledAccessibilityServices();
                             }
                 })
                 .setNegativeButton(android.R.string.cancel,
                         new DialogInterface.OnClickListener() {
                             public void onClick(DialogInterface dialog, int which) {
                                 checkBoxPreference.setChecked(false);
                             }
                 })
                 .create();
             dialog.show();
         } else {
             persistEnabledAccessibilityServices();
         }
     }

     /**
      * Persists the Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES setting.
      * The AccessibilityManagerService watches this property and manages the
      * AccessibilityServices.
      */
     private void persistEnabledAccessibilityServices() {
         StringBuilder builder = new StringBuilder(256);

         int firstEnabled = -1;
         for (String key : mAccessibilityServices.keySet()) {
             CheckBoxPreference preference = (CheckBoxPreference) findPreference(key);
             if (preference.isChecked()) {
                  builder.append(key);
                  builder.append(':');
             }
         }

         Settings.Secure.putString(getContentResolver(),
             Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES, builder.toString());
     }

     /**
      * Adds {@link CheckBoxPreference} for enabling or disabling an accessibility services.
      */
     private void addAccessibilitServicePreferences() {
         AccessibilityManager accessibilityManager =
             (AccessibilityManager) getSystemService(Service.ACCESSIBILITY_SERVICE);

         List<ServiceInfo> installedServices = accessibilityManager.getAccessibilityServiceList();

         mAccessibilityServicesCategory =
             (PreferenceGroup) findPreference(ACCESSIBILITY_SERVICES_CATEGORY);

         if (installedServices.isEmpty()) {
             getPreferenceScreen().removePreference(mAccessibilityServicesCategory);
             mAccessibilityServicesCategory = null;
             return;
         }

         for (int i = 0, count = installedServices.size(); i < count; ++i) {
             ServiceInfo serviceInfo = installedServices.get(i);
             String key = serviceInfo.packageName + "/" + serviceInfo.name;

             mAccessibilityServices.put(key, serviceInfo);

             CheckBoxPreference preference = new CheckBoxPreference(this);
             preference.setKey(key);
             preference.setTitle(serviceInfo.loadLabel(getPackageManager()));
             mAccessibilityServicesCategory.addPreference(preference);
         }
     }

     /**
      * Displays a message telling the user that they do not have any accessibility
      * related apps installed and that they can get TalkBack (Google's free screen
      * reader) from Market.
      */
     private void displayNoAppsAlert() {
         try {
             PackageManager pm = getPackageManager();
             ApplicationInfo info = pm.getApplicationInfo("com.android.vending", 0);
         } catch (NameNotFoundException e) {
             // This is a no-op if the user does not have Android Market
             return;
         }
         AlertDialog.Builder noAppsAlert = new AlertDialog.Builder(this);
         noAppsAlert.setTitle(R.string.accessibility_service_no_apps_title);
         noAppsAlert.setMessage(R.string.accessibility_service_no_apps_message);

         noAppsAlert.setPositiveButton(android.R.string.ok,
             new DialogInterface.OnClickListener() {
                 public void onClick(DialogInterface dialog, int which) {
                     String screenreaderMarketLink =
                         SystemProperties.get("ro.screenreader.market",
                                 DEFAULT_SCREENREADER_MARKET_LINK);
                     Uri marketUri = Uri.parse(screenreaderMarketLink);
                     Intent marketIntent = new Intent(Intent.ACTION_VIEW, marketUri);
                     startActivity(marketIntent);
                     finish();
                 }
             });

         noAppsAlert.setNegativeButton(android.R.string.cancel,
             new DialogInterface.OnClickListener() {
                 public void onClick(DialogInterface dialog, int which) {
                 }
             });

         noAppsAlert.show();
     }
 }
	/*
	* Copyright (C) 2009 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.settings;

	import android.app.AlertDialog;
	import android.app.Service;
	import android.content.DialogInterface;
	import android.content.Intent;
	import android.content.pm.ApplicationInfo;
	import android.content.pm.PackageManager;
	import android.content.pm.PackageManager.NameNotFoundException;
	import android.content.pm.ServiceInfo;
	import android.net.Uri;
	import android.os.Bundle;
	import android.os.SystemProperties;
	import android.preference.CheckBoxPreference;
	import android.preference.Preference;
	import android.preference.PreferenceActivity;
	import android.preference.PreferenceCategory;
	import android.preference.PreferenceGroup;
	import android.preference.PreferenceScreen;
	import android.provider.Settings;
	import android.text.TextUtils;
	import android.view.KeyCharacterMap;
	import android.view.KeyEvent;
	import android.view.accessibility.AccessibilityManager;

	import java.util.HashSet;
	import java.util.LinkedHashMap;
	import java.util.List;
	import java.util.Map;

	/**
	* Activity with the accessibility settings.
	*/
	public class AccessibilitySettings extends PreferenceActivity {
	private static final String DEFAULT_SCREENREADER_MARKET_LINK =
	"market://search?q=pname:com.google.android.marvin.talkback";

	private final String TOGGLE_ACCESSIBILITY_SERVICE_CHECKBOX =
	"toggle_accessibility_service_checkbox";

	private static final String ACCESSIBILITY_SERVICES_CATEGORY =
	"accessibility_services_category";

	private static final String POWER_BUTTON_CATEGORY =
	"power_button_category";

	private final String POWER_BUTTON_ENDS_CALL_CHECKBOX =
	"power_button_ends_call";

	private CheckBoxPreference mToggleCheckBox;

	private PreferenceCategory mPowerButtonCategory;
	private CheckBoxPreference mPowerButtonEndsCallCheckBox;

	private Map<String, ServiceInfo> mAccessibilityServices =
	new LinkedHashMap<String, ServiceInfo>();

	private TextUtils.SimpleStringSplitter mStringColonSplitter =
	new TextUtils.SimpleStringSplitter(':');

	private PreferenceGroup mAccessibilityServicesCategory;

	@Override
	protected void onCreate(Bundle icicle) {
	super.onCreate(icicle);
	addPreferencesFromResource(R.xml.accessibility_settings);

	mToggleCheckBox = (CheckBoxPreference) findPreference(
	TOGGLE_ACCESSIBILITY_SERVICE_CHECKBOX);

	mPowerButtonCategory = (PreferenceCategory) findPreference(POWER_BUTTON_CATEGORY);
	mPowerButtonEndsCallCheckBox = (CheckBoxPreference) findPreference(
	POWER_BUTTON_ENDS_CALL_CHECKBOX);

	addAccessibilitServicePreferences();
	}

	@Override
	protected void onResume() {
	super.onResume();

	final HashSet<String> enabled = new HashSet<String>();
	String settingValue = Settings.Secure.getString(getContentResolver(),
	Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES);
	if (settingValue != null) {
	TextUtils.SimpleStringSplitter splitter = mStringColonSplitter;
	splitter.setString(settingValue);
	while (splitter.hasNext()) {
	enabled.add(splitter.next());
	}
	}

	Map<String, ServiceInfo> accessibilityServices = mAccessibilityServices;

	for (String key : accessibilityServices.keySet()) {
	CheckBoxPreference preference = (CheckBoxPreference) findPreference(key);
	if (preference != null) {
	preference.setChecked(enabled.contains(key));
	}
	}

	int serviceState = Settings.Secure.getInt(getContentResolver(),
	Settings.Secure.ACCESSIBILITY_ENABLED, 0);

	if (!accessibilityServices.isEmpty()) {
	if (serviceState == 1) {
	mToggleCheckBox.setChecked(true);
	} else {
	setAccessibilityServicePreferencesState(false);
	}
	mToggleCheckBox.setEnabled(true);
	} else {
	if (serviceState == 1) {
	// no service and accessibility is enabled => disable
	Settings.Secure.putInt(getContentResolver(),
	Settings.Secure.ACCESSIBILITY_ENABLED, 0);
	}
	mToggleCheckBox.setEnabled(false);
	// Notify user that they do not have any accessibility apps
	// installed and direct them to Market to get TalkBack
	displayNoAppsAlert();
	}

	if (KeyCharacterMap.deviceHasKey(KeyEvent.KEYCODE_POWER)) {
	int incallPowerBehavior = Settings.Secure.getInt(getContentResolver(),
	Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR,
	Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_DEFAULT);
	// The checkbox is labeled "Power button ends call"; thus the in-call
	// Power button behavior is INCALL_POWER_BUTTON_BEHAVIOR_HANGUP if
	// checked, and INCALL_POWER_BUTTON_BEHAVIOR_SCREEN_OFF if unchecked.
	boolean powerButtonCheckboxEnabled =
	(incallPowerBehavior == Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP);
	mPowerButtonEndsCallCheckBox.setChecked(powerButtonCheckboxEnabled);
	mPowerButtonEndsCallCheckBox.setEnabled(true);
	} else {
	// No POWER key on the current device; this entire category is irrelevant.
	getPreferenceScreen().removePreference(mPowerButtonCategory);
	}
	}

	@Override
	protected void onPause() {
	super.onPause();

	persistEnabledAccessibilityServices();
	}

	/**
	* Sets the state of the preferences for enabling/disabling
	* AccessibilityServices.
	*
	* @param isEnabled If to enable or disable the preferences.
	*/
	private void setAccessibilityServicePreferencesState(boolean isEnabled) {
	if (mAccessibilityServicesCategory == null) {
	return;
	}

	int count = mAccessibilityServicesCategory.getPreferenceCount();
	for (int i = 0; i < count; i++) {
	Preference pref = mAccessibilityServicesCategory.getPreference(i);
	pref.setEnabled(isEnabled);
	}
	}

	@Override
	public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) {
	final String key = preference.getKey();

	if (TOGGLE_ACCESSIBILITY_SERVICE_CHECKBOX.equals(key)) {
	boolean isChecked = ((CheckBoxPreference) preference).isChecked();
	handleEnableAccessibilityStateChange((CheckBoxPreference) preference);
	} else if (POWER_BUTTON_ENDS_CALL_CHECKBOX.equals(key)) {
	boolean isChecked = ((CheckBoxPreference) preference).isChecked();
	// The checkbox is labeled "Power button ends call"; thus the in-call
	// Power button behavior is INCALL_POWER_BUTTON_BEHAVIOR_HANGUP if
	// checked, and INCALL_POWER_BUTTON_BEHAVIOR_SCREEN_OFF if unchecked.
	Settings.Secure.putInt(getContentResolver(),
	Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR,
	(isChecked ? Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP
	: Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_SCREEN_OFF));
	} else if (preference instanceof CheckBoxPreference) {
	handleEnableAccessibilityServiceStateChange((CheckBoxPreference) preference);
	}

	return super.onPreferenceTreeClick(preferenceScreen, preference);
	}

	/**
	* Handles the change of the accessibility enabled setting state.
	*
	* @param preference The preference for enabling/disabling accessibility.
	*/
	private void handleEnableAccessibilityStateChange(CheckBoxPreference preference) {
	if (preference.isChecked()) {
	Settings.Secure.putInt(getContentResolver(),
	Settings.Secure.ACCESSIBILITY_ENABLED, 1);
	setAccessibilityServicePreferencesState(true);
	} else {
	final CheckBoxPreference checkBoxPreference = preference;
	AlertDialog dialog = (new AlertDialog.Builder(this))
	.setTitle(android.R.string.dialog_alert_title)
	.setIcon(android.R.drawable.ic_dialog_alert)
	.setMessage(getString(R.string.accessibility_service_disable_warning))
	.setCancelable(true)
	.setPositiveButton(android.R.string.ok,
	new DialogInterface.OnClickListener() {
	public void onClick(DialogInterface dialog, int which) {
	Settings.Secure.putInt(getContentResolver(),
	Settings.Secure.ACCESSIBILITY_ENABLED, 0);
	setAccessibilityServicePreferencesState(false);
	}
	})
	.setNegativeButton(android.R.string.cancel,
	new DialogInterface.OnClickListener() {
	public void onClick(DialogInterface dialog, int which) {
	checkBoxPreference.setChecked(true);
	}
	})
	.create();
	dialog.show();
	}
	}

	/**
	* Handles the change of the preference for enabling/disabling an AccessibilityService.
	*
	* @param preference The preference.
	*/
	private void handleEnableAccessibilityServiceStateChange(CheckBoxPreference preference) {
	if (preference.isChecked()) {
	final CheckBoxPreference checkBoxPreference = preference;
	AlertDialog dialog = (new AlertDialog.Builder(this))
	.setTitle(android.R.string.dialog_alert_title)
	.setIcon(android.R.drawable.ic_dialog_alert)
	.setMessage(getString(R.string.accessibility_service_security_warning,
	mAccessibilityServices.get(preference.getKey())
	.applicationInfo.loadLabel(getPackageManager())))
	.setCancelable(true)
	.setPositiveButton(android.R.string.ok,
	new DialogInterface.OnClickListener() {
	public void onClick(DialogInterface dialog, int which) {
	checkBoxPreference.setChecked(true);
	persistEnabledAccessibilityServices();
	}
	})
	.setNegativeButton(android.R.string.cancel,
	new DialogInterface.OnClickListener() {
	public void onClick(DialogInterface dialog, int which) {
	checkBoxPreference.setChecked(false);
	}
	})
	.create();
	dialog.show();
	} else {
	persistEnabledAccessibilityServices();
	}
	}

	/**
	* Persists the Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES setting.
	* The AccessibilityManagerService watches this property and manages the
	* AccessibilityServices.
	*/
	private void persistEnabledAccessibilityServices() {
	StringBuilder builder = new StringBuilder(256);

	int firstEnabled = -1;
	for (String key : mAccessibilityServices.keySet()) {
	CheckBoxPreference preference = (CheckBoxPreference) findPreference(key);
	if (preference.isChecked()) {
	builder.append(key);
	builder.append(':');
	}
	}

	Settings.Secure.putString(getContentResolver(),
	Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES, builder.toString());
	}

	/**
	* Adds {@link CheckBoxPreference} for enabling or disabling an accessibility services.
	*/
	private void addAccessibilitServicePreferences() {
	AccessibilityManager accessibilityManager =
	(AccessibilityManager) getSystemService(Service.ACCESSIBILITY_SERVICE);

	List<ServiceInfo> installedServices = accessibilityManager.getAccessibilityServiceList();

	mAccessibilityServicesCategory =
	(PreferenceGroup) findPreference(ACCESSIBILITY_SERVICES_CATEGORY);

	if (installedServices.isEmpty()) {
	getPreferenceScreen().removePreference(mAccessibilityServicesCategory);
	mAccessibilityServicesCategory = null;
	return;
	}

	for (int i = 0, count = installedServices.size(); i < count; ++i) {
	ServiceInfo serviceInfo = installedServices.get(i);
	String key = serviceInfo.packageName + "/" + serviceInfo.name;

	mAccessibilityServices.put(key, serviceInfo);

	CheckBoxPreference preference = new CheckBoxPreference(this);
	preference.setKey(key);
	preference.setTitle(serviceInfo.loadLabel(getPackageManager()));
	mAccessibilityServicesCategory.addPreference(preference);
	}
	}

	/**
	* Displays a message telling the user that they do not have any accessibility
	* related apps installed and that they can get TalkBack (Google's free screen
	* reader) from Market.
	*/
	private void displayNoAppsAlert() {
	try {
	PackageManager pm = getPackageManager();
	ApplicationInfo info = pm.getApplicationInfo("com.android.vending", 0);
	} catch (NameNotFoundException e) {
	// This is a no-op if the user does not have Android Market
	return;
	}
	AlertDialog.Builder noAppsAlert = new AlertDialog.Builder(this);
	noAppsAlert.setTitle(R.string.accessibility_service_no_apps_title);
	noAppsAlert.setMessage(R.string.accessibility_service_no_apps_message);

	noAppsAlert.setPositiveButton(android.R.string.ok,
	new DialogInterface.OnClickListener() {
	public void onClick(DialogInterface dialog, int which) {
	String screenreaderMarketLink =
	SystemProperties.get("ro.screenreader.market",
	DEFAULT_SCREENREADER_MARKET_LINK);
	Uri marketUri = Uri.parse(screenreaderMarketLink);
	Intent marketIntent = new Intent(Intent.ACTION_VIEW, marketUri);
	startActivity(marketIntent);
	finish();
	}
	});

	noAppsAlert.setNegativeButton(android.R.string.cancel,
	new DialogInterface.OnClickListener() {
	public void onClick(DialogInterface dialog, int which) {
	}
	});

	noAppsAlert.show();
	}
	}