src/com/android/camera/settings/SettingsManager.java - platform/packages/apps/Camera2 - Git at Google

 /*
  * Copyright (C) 2013 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.camera.settings;

 import android.content.Context;
 import android.content.SharedPreferences;
 import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
 import android.preference.PreferenceManager;

 import com.android.camera.debug.Log;
 import com.android.camera.util.Size;

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

 /**
  * SettingsManager class provides an api for getting and setting SharedPreferences
  * values.
  *
  * Types
  *
  * This API simplifies settings type management by storing all settings values
  * in SharedPreferences as Strings.  To do this, the API to converts boolean and
  * Integer values to Strings when those values are stored, making the conversion
  * back to a boolean or Integer also consistent and simple.
  *
  * This also enables the user to safely get settings values as three different types,
  * as it's convenient: String, Integer, and boolean values.  Integers and boolean
  * can always be trivially converted to one another, but Strings cannot always be
  * parsed as Integers.  In this case, if the user stores a String value that cannot
  * be parsed to an Integer yet they try to retrieve it as an Integer, the API throws
  * a meaningful exception to the user.
  *
  * Scope
  *
  * This API introduces the concept of "scope" for a setting, which is the generality
  * of a setting.  The most general settings, that can be accessed acrossed the
  * entire application, have a scope of SCOPE_GLOBAL.  They are stored in the default
  * SharedPreferences file.
  *
  * A setting that is local to a third party module or subset of the application has
  * a custom scope.  The specific module can define whatever scope (String) argument
  * they want, and the settings saved with that scope can only be seen by that third
  * party module.  Scope is a general concept that helps protect settings values
  * from being clobbered in different contexts.
  *
  * Keys and Defaults
  *
  * This API allows you to store your SharedPreferences keys and default values
  * outside the SettingsManager, because these values are either passed into
  * the API or stored in a cache when the user sets defaults.
  *
  * For any setting, it is optional to store a default or set of possible values,
  * unless you plan on using the getIndexOfCurrentValue and setValueByIndex,
  * methods, which rely on an index into the set of possible values.
  *
  */
 public class SettingsManager {
     private static final Log.Tag TAG = new Log.Tag("SettingsManager");

     private final Context mContext;
     private final String mPackageName;
     private final SharedPreferences mDefaultPreferences;
     private SharedPreferences mCustomPreferences;
     private final DefaultsStore mDefaultsStore = new DefaultsStore();

     /**
      * A List of OnSettingChangedListener's, maintained to compare to new
      * listeners and prevent duplicate registering.
      */
     private final List<OnSettingChangedListener> mListeners =
         new ArrayList<OnSettingChangedListener>();

     /**
      * A List of OnSharedPreferenceChangeListener's, maintained to hold pointers
      * to actually registered listeners, so they can be unregistered.
      */
     private final List<OnSharedPreferenceChangeListener> mSharedPreferenceListeners =
         new ArrayList<OnSharedPreferenceChangeListener>();

     public SettingsManager(Context context) {
         mContext = context;
         mPackageName = mContext.getPackageName();

         mDefaultPreferences = PreferenceManager.getDefaultSharedPreferences(mContext);
     }

     /**
      * Get the SettingsManager's default preferences.  This is useful
      * to third party modules as they are defining their upgrade paths,
      * since most third party modules will use either SCOPE_GLOBAL or a
      * custom scope.
      */
     public SharedPreferences getDefaultPreferences() {
         return mDefaultPreferences;
     }

     /**
      * Open a SharedPreferences file by custom scope.
      * Also registers any known SharedPreferenceListeners on this
      * SharedPreferences instance.
      */
     protected SharedPreferences openPreferences(String scope) {
         SharedPreferences preferences = mContext.getSharedPreferences(
             mPackageName + scope, Context.MODE_PRIVATE);

         for (OnSharedPreferenceChangeListener listener : mSharedPreferenceListeners) {
             preferences.registerOnSharedPreferenceChangeListener(listener);
         }

         return preferences;
     }

     /**
      * Close a SharedPreferences file by custom scope.
      * The file isn't explicitly closed (the SharedPreferences API makes
      * this unnecessary), so the real work is to unregister any known
      * SharedPreferenceListeners from this SharedPreferences instance.
      *
      * It's important to do this as camera and modules change, because
      * we don't want old SharedPreferences listeners executing on
      * cameras/modules they are not compatible with.
      */
     protected void closePreferences(SharedPreferences preferences) {
         for (OnSharedPreferenceChangeListener listener : mSharedPreferenceListeners) {
             preferences.unregisterOnSharedPreferenceChangeListener(listener);
         }
     }

     /**
      * Interface with Camera Device Settings and Modules.
      */
     public interface OnSettingChangedListener {
         /**
          * Called every time a SharedPreference has been changed.
          */
 	public void onSettingChanged(SettingsManager settingsManager, String key);
     }

     private OnSharedPreferenceChangeListener getSharedPreferenceListener(
             final OnSettingChangedListener listener) {
         return new OnSharedPreferenceChangeListener() {
             @Override
             public void onSharedPreferenceChanged(
                     SharedPreferences sharedPreferences, String key) {
 		listener.onSettingChanged(SettingsManager.this, key);
             }
         };
     }

     /**
      * Add an OnSettingChangedListener to the SettingsManager, which will
      * execute onSettingsChanged when any SharedPreference has been updated.
      */
     public void addListener(final OnSettingChangedListener listener) {
         if (listener == null) {
             throw new IllegalArgumentException("OnSettingChangedListener cannot be null.");
         }

         if (mListeners.contains(listener)) {
             return;
         }

         mListeners.add(listener);
         OnSharedPreferenceChangeListener sharedPreferenceListener =
                 getSharedPreferenceListener(listener);
         mSharedPreferenceListeners.add(sharedPreferenceListener);
         mDefaultPreferences.registerOnSharedPreferenceChangeListener(sharedPreferenceListener);

         if (mCustomPreferences != null) {
             mCustomPreferences.registerOnSharedPreferenceChangeListener(
                 sharedPreferenceListener);
         }
         Log.v(TAG, "listeners: " + mListeners);
     }

     /**
      * Remove a specific SettingsListener. This should be done in onPause if a
      * listener has been set.
      */
     public void removeListener(OnSettingChangedListener listener) {
         if (listener == null) {
             throw new IllegalArgumentException();
         }

         if (!mListeners.contains(listener)) {
             return;
         }

         int index = mListeners.indexOf(listener);
         mListeners.remove(listener);

         OnSharedPreferenceChangeListener sharedPreferenceListener =
                 mSharedPreferenceListeners.get(index);
         mSharedPreferenceListeners.remove(index);
         mDefaultPreferences.unregisterOnSharedPreferenceChangeListener(
                 sharedPreferenceListener);

         if (mCustomPreferences != null) {
             mCustomPreferences.unregisterOnSharedPreferenceChangeListener(
                 sharedPreferenceListener);
         }
     }

     /**
      * Remove all OnSharedPreferenceChangedListener's. This should be done in
      * onDestroy.
      */
     public void removeAllListeners() {
         for (OnSharedPreferenceChangeListener listener : mSharedPreferenceListeners) {
             mDefaultPreferences.unregisterOnSharedPreferenceChangeListener(listener);

             if (mCustomPreferences != null) {
                 mCustomPreferences.unregisterOnSharedPreferenceChangeListener(listener);
             }
         }
         mSharedPreferenceListeners.clear();
         mListeners.clear();
     }

     /** This scope stores and retrieves settings from
         default preferences. */
     public static final String SCOPE_GLOBAL = "default_scope";

     /**
      * Returns the SharedPreferences file matching the scope
      * argument.
      *
      * Camera and module preferences files are cached,
      * until the camera id or module id changes, then the listeners
      * are unregistered and a new file is opened.
      */
     private SharedPreferences getPreferencesFromScope(String scope) {
         if (scope.equals(SCOPE_GLOBAL)) {
             return mDefaultPreferences;
         }

         if (mCustomPreferences != null) {
             closePreferences(mCustomPreferences);
         }
         mCustomPreferences = openPreferences(scope);
         return mCustomPreferences;
     }

     /**
      * Set default and valid values for a setting, for a String default and
      * a set of String possible values that are already defined.
      * This is not required.
      */
     public void setDefaults(String key, String defaultValue, String[] possibleValues) {
         mDefaultsStore.storeDefaults(key, defaultValue, possibleValues);
     }

     /**
      * Set default and valid values for a setting, for an Integer default and
      * a set of Integer possible values that are already defined.
      * This is not required.
      */
     public void setDefaults(String key, int defaultValue, int[] possibleValues) {
         String defaultValueString = Integer.toString(defaultValue);
         String[] possibleValuesString = new String[possibleValues.length];
         for (int i = 0; i < possibleValues.length; i++) {
             possibleValuesString[i] = Integer.toString(possibleValues[i]);
         }
         mDefaultsStore.storeDefaults(key, defaultValueString, possibleValuesString);
     }

     /**
      * Set default and valid values for a setting, for a boolean default.
      * The set of boolean possible values is always { false, true }.
      * This is not required.
      */
     public void setDefaults(String key, boolean defaultValue) {
         String defaultValueString = defaultValue ? "1" : "0";
         String[] possibleValues = { "0", "1" };
         mDefaultsStore.storeDefaults(key, defaultValueString, possibleValues);
     }

     /**
      * Retrieve a default from the DefaultsStore as a String.
      */
     public String getStringDefault(String key) {
         return mDefaultsStore.getDefaultValue(key);
     }

     /**
      * Retrieve a default from the DefaultsStore as an Integer.
      */
     public Integer getIntegerDefault(String key) {
         String defaultValueString = mDefaultsStore.getDefaultValue(key);
         return defaultValueString == null ? 0 : Integer.parseInt(defaultValueString);
     }

     /**
      * Retrieve a default from the DefaultsStore as a boolean.
      */
     public boolean getBooleanDefault(String key) {
         String defaultValueString = mDefaultsStore.getDefaultValue(key);
         return defaultValueString == null ? false :
             (Integer.parseInt(defaultValueString) != 0);
     }

     /**
      * Retrieve a setting's value as a String, manually specifiying
      * a default value.
      */
     public String getString(String scope, String key, String defaultValue) {
         SharedPreferences preferences = getPreferencesFromScope(scope);
         try {
             return preferences.getString(key, defaultValue);
         } catch (ClassCastException e) {
             Log.w(TAG, "existing preference with invalid type, removing and returning default", e);
             preferences.edit().remove(key).apply();
             return defaultValue;
         }
     }

     /**
      * Retrieve a setting's value as a String, using the default value
      * stored in the DefaultsStore.
      */
     public String getString(String scope, String key) {
         return getString(scope, key, getStringDefault(key));
     }

     /**
      * Retrieve a setting's value as an Integer, manually specifying
      * a default value.
      */
     public Integer getInteger(String scope, String key, Integer defaultValue) {
         String defaultValueString = Integer.toString(defaultValue);
         String value = getString(scope, key, defaultValueString);
         return convertToInt(value);
     }

     /**
      * Retrieve a setting's value as an Integer, converting the default value
      * stored in the DefaultsStore.
      */
     public Integer getInteger(String scope, String key) {
         return getInteger(scope, key, getIntegerDefault(key));
     }

     /**
      * Retrieve a setting's value as a boolean, manually specifiying
      * a default value.
      */
     public boolean getBoolean(String scope, String key, boolean defaultValue) {
         String defaultValueString = defaultValue ? "1" : "0";
         String value = getString(scope, key, defaultValueString);
         return convertToBoolean(value);
     }

     /**
      * Retrieve a setting's value as a boolean, converting the default value
      * stored in the DefaultsStore.
      */
     public boolean getBoolean(String scope, String key) {
         return getBoolean(scope, key, getBooleanDefault(key));
     }

     /**
      * Retrieve a setting's value as a {@link Size}. Returns <code>null</code>
      * if value could not be parsed as a size.
      */
     public Size getSize(String scope, String key) {
         String strValue = getString(scope, key);
         if (strValue == null) {
             return null;
         }

         String[] widthHeight = strValue.split("x");
         if (widthHeight.length != 2) {
             return null;
         }

         try {
             int width = Integer.parseInt(widthHeight[0]);
             int height = Integer.parseInt(widthHeight[1]);
             return new Size(width, height);
         } catch (NumberFormatException ex) {
             return null;
         }
     }

     /**
      * If possible values are stored for this key, return the
      * index into that list of the currently set value.
      *
      * For example, if a set of possible values is [2,3,5],
      * and the current value set of this key is 3, this method
      * returns 1.
      *
      * If possible values are not stored for this key, throw
      * an IllegalArgumentException.
      */
     public int getIndexOfCurrentValue(String scope, String key) {
         String[] possibleValues = mDefaultsStore.getPossibleValues(key);
         if (possibleValues == null || possibleValues.length == 0) {
             throw new IllegalArgumentException(
                 "No possible values for scope=" + scope + " key=" + key);
         }

         String value = getString(scope, key);
         for (int i = 0; i < possibleValues.length; i++) {
             if (value.equals(possibleValues[i])) {
                 return i;
             }
         }
         throw new IllegalStateException("Current value for scope=" + scope + " key="
                                         + key + " not in list of possible values");
     }

     /**
      * Store a setting's value using a String value.  No conversion
      * occurs before this value is stored in SharedPreferences.
      */
     public void set(String scope, String key, String value) {
         SharedPreferences preferences = getPreferencesFromScope(scope);
         preferences.edit().putString(key, value).apply();
     }

     /**
      * Store a setting's value using an Integer value.  Type conversion
      * to String occurs before this value is stored in SharedPreferences.
      */
     public void set(String scope, String key, int value) {
         set(scope, key, convert(value));
     }

     /**
      * Store a setting's value using a boolean value.  Type conversion
      * to an Integer and then to a String occurs before this value is
      * stored in SharedPreferences.
      */
     public void set(String scope, String key, boolean value) {
         set(scope, key, convert(value));
     }

     /**
      * Set a setting to the default value stored in the DefaultsStore.
      */
     public void setToDefault(String scope, String key) {
         set(scope, key, getStringDefault(key));
     }

     /**
      * If a set of possible values is defined, set the current value
      * of a setting to the possible value found at the given index.
      *
      * For example, if the possible values for a key are [2,3,5],
      * and the index given to this method is 2, then this method would
      * store the value 5 in SharedPreferences for the key.
      *
      * If the index is out of the bounds of the range of possible values,
      * or there are no possible values for this key, then this
      * method throws an exception.
      */
     public void setValueByIndex(String scope, String key, int index) {
         String[] possibleValues = mDefaultsStore.getPossibleValues(key);
         if (possibleValues.length == 0) {
             throw new IllegalArgumentException(
                 "No possible values for scope=" + scope + " key=" + key);
         }

         if (index >= 0 && index < possibleValues.length) {
             set(scope, key, possibleValues[index]);
         } else {
             throw new IndexOutOfBoundsException("For possible values of scope=" + scope
                                                 + " key=" + key);
         }
     }

     /**
      * Check that a setting has some value stored.
      */
     public boolean isSet(String scope, String key) {
         SharedPreferences preferences = getPreferencesFromScope(scope);
         return preferences.contains(key);
     }

     /**
      * Check whether a settings's value is currently set to the
      * default value.
      */
     public boolean isDefault(String scope, String key) {
         String defaultValue = getStringDefault(key);
         String value = getString(scope, key);
         return value == null ? false : value.equals(defaultValue);
     }

     /**
      * Remove a setting.
      */
     public void remove(String scope, String key) {
         SharedPreferences preferences = getPreferencesFromScope(scope);
         preferences.edit().remove(key).apply();
     }

     /**
      * Package private conversion method to turn ints into preferred
      * String storage format.
      *
      * @param value int to be stored in Settings
      * @return String which represents the int
      */
     static String convert(int value) {
         return Integer.toString(value);
     }

     /**
      * Package private conversion method to turn String storage format into
      * ints.
      *
      * @param value String to be converted to int
      * @return int value of stored String
      */
     static int convertToInt(String value) {
         return Integer.parseInt(value);
     }

     /**
      * Package private conversion method to turn String storage format into
      * booleans.
      *
      * @param value String to be converted to boolean
      * @return boolean value of stored String
      */
     static boolean convertToBoolean(String value) {
         return Integer.parseInt(value) != 0;
     }


     /**
      * Package private conversion method to turn booleans into preferred
      * String storage format.
      *
      * @param value boolean to be stored in Settings
      * @return String which represents the boolean
      */
     static String convert(boolean value) {
         return value ? "1" : "0";
     }
 }
	/*
	* Copyright (C) 2013 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.camera.settings;

	import android.content.Context;
	import android.content.SharedPreferences;
	import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
	import android.preference.PreferenceManager;

	import com.android.camera.debug.Log;
	import com.android.camera.util.Size;

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

	/**
	* SettingsManager class provides an api for getting and setting SharedPreferences
	* values.
	*
	* Types
	*
	* This API simplifies settings type management by storing all settings values
	* in SharedPreferences as Strings. To do this, the API to converts boolean and
	* Integer values to Strings when those values are stored, making the conversion
	* back to a boolean or Integer also consistent and simple.
	*
	* This also enables the user to safely get settings values as three different types,
	* as it's convenient: String, Integer, and boolean values. Integers and boolean
	* can always be trivially converted to one another, but Strings cannot always be
	* parsed as Integers. In this case, if the user stores a String value that cannot
	* be parsed to an Integer yet they try to retrieve it as an Integer, the API throws
	* a meaningful exception to the user.
	*
	* Scope
	*
	* This API introduces the concept of "scope" for a setting, which is the generality
	* of a setting. The most general settings, that can be accessed acrossed the
	* entire application, have a scope of SCOPE_GLOBAL. They are stored in the default
	* SharedPreferences file.
	*
	* A setting that is local to a third party module or subset of the application has
	* a custom scope. The specific module can define whatever scope (String) argument
	* they want, and the settings saved with that scope can only be seen by that third
	* party module. Scope is a general concept that helps protect settings values
	* from being clobbered in different contexts.
	*
	* Keys and Defaults
	*
	* This API allows you to store your SharedPreferences keys and default values
	* outside the SettingsManager, because these values are either passed into
	* the API or stored in a cache when the user sets defaults.
	*
	* For any setting, it is optional to store a default or set of possible values,
	* unless you plan on using the getIndexOfCurrentValue and setValueByIndex,
	* methods, which rely on an index into the set of possible values.
	*
	*/
	public class SettingsManager {
	private static final Log.Tag TAG = new Log.Tag("SettingsManager");

	private final Context mContext;
	private final String mPackageName;
	private final SharedPreferences mDefaultPreferences;
	private SharedPreferences mCustomPreferences;
	private final DefaultsStore mDefaultsStore = new DefaultsStore();

	/**
	* A List of OnSettingChangedListener's, maintained to compare to new
	* listeners and prevent duplicate registering.
	*/
	private final List<OnSettingChangedListener> mListeners =
	new ArrayList<OnSettingChangedListener>();

	/**
	* A List of OnSharedPreferenceChangeListener's, maintained to hold pointers
	* to actually registered listeners, so they can be unregistered.
	*/
	private final List<OnSharedPreferenceChangeListener> mSharedPreferenceListeners =
	new ArrayList<OnSharedPreferenceChangeListener>();

	public SettingsManager(Context context) {
	mContext = context;
	mPackageName = mContext.getPackageName();

	mDefaultPreferences = PreferenceManager.getDefaultSharedPreferences(mContext);
	}

	/**
	* Get the SettingsManager's default preferences. This is useful
	* to third party modules as they are defining their upgrade paths,
	* since most third party modules will use either SCOPE_GLOBAL or a
	* custom scope.
	*/
	public SharedPreferences getDefaultPreferences() {
	return mDefaultPreferences;
	}

	/**
	* Open a SharedPreferences file by custom scope.
	* Also registers any known SharedPreferenceListeners on this
	* SharedPreferences instance.
	*/
	protected SharedPreferences openPreferences(String scope) {
	SharedPreferences preferences = mContext.getSharedPreferences(
	mPackageName + scope, Context.MODE_PRIVATE);

	for (OnSharedPreferenceChangeListener listener : mSharedPreferenceListeners) {
	preferences.registerOnSharedPreferenceChangeListener(listener);
	}

	return preferences;
	}

	/**
	* Close a SharedPreferences file by custom scope.
	* The file isn't explicitly closed (the SharedPreferences API makes
	* this unnecessary), so the real work is to unregister any known
	* SharedPreferenceListeners from this SharedPreferences instance.
	*
	* It's important to do this as camera and modules change, because
	* we don't want old SharedPreferences listeners executing on
	* cameras/modules they are not compatible with.
	*/
	protected void closePreferences(SharedPreferences preferences) {
	for (OnSharedPreferenceChangeListener listener : mSharedPreferenceListeners) {
	preferences.unregisterOnSharedPreferenceChangeListener(listener);
	}
	}

	/**
	* Interface with Camera Device Settings and Modules.
	*/
	public interface OnSettingChangedListener {
	/**
	* Called every time a SharedPreference has been changed.
	*/
	public void onSettingChanged(SettingsManager settingsManager, String key);
	}

	private OnSharedPreferenceChangeListener getSharedPreferenceListener(
	final OnSettingChangedListener listener) {
	return new OnSharedPreferenceChangeListener() {
	@Override
	public void onSharedPreferenceChanged(
	SharedPreferences sharedPreferences, String key) {
	listener.onSettingChanged(SettingsManager.this, key);
	}
	};
	}

	/**
	* Add an OnSettingChangedListener to the SettingsManager, which will
	* execute onSettingsChanged when any SharedPreference has been updated.
	*/
	public void addListener(final OnSettingChangedListener listener) {
	if (listener == null) {
	throw new IllegalArgumentException("OnSettingChangedListener cannot be null.");
	}

	if (mListeners.contains(listener)) {
	return;
	}

	mListeners.add(listener);
	OnSharedPreferenceChangeListener sharedPreferenceListener =
	getSharedPreferenceListener(listener);
	mSharedPreferenceListeners.add(sharedPreferenceListener);
	mDefaultPreferences.registerOnSharedPreferenceChangeListener(sharedPreferenceListener);

	if (mCustomPreferences != null) {
	mCustomPreferences.registerOnSharedPreferenceChangeListener(
	sharedPreferenceListener);
	}
	Log.v(TAG, "listeners: " + mListeners);
	}

	/**
	* Remove a specific SettingsListener. This should be done in onPause if a
	* listener has been set.
	*/
	public void removeListener(OnSettingChangedListener listener) {
	if (listener == null) {
	throw new IllegalArgumentException();
	}

	if (!mListeners.contains(listener)) {
	return;
	}

	int index = mListeners.indexOf(listener);
	mListeners.remove(listener);

	OnSharedPreferenceChangeListener sharedPreferenceListener =
	mSharedPreferenceListeners.get(index);
	mSharedPreferenceListeners.remove(index);
	mDefaultPreferences.unregisterOnSharedPreferenceChangeListener(
	sharedPreferenceListener);

	if (mCustomPreferences != null) {
	mCustomPreferences.unregisterOnSharedPreferenceChangeListener(
	sharedPreferenceListener);
	}
	}

	/**
	* Remove all OnSharedPreferenceChangedListener's. This should be done in
	* onDestroy.
	*/
	public void removeAllListeners() {
	for (OnSharedPreferenceChangeListener listener : mSharedPreferenceListeners) {
	mDefaultPreferences.unregisterOnSharedPreferenceChangeListener(listener);

	if (mCustomPreferences != null) {
	mCustomPreferences.unregisterOnSharedPreferenceChangeListener(listener);
	}
	}
	mSharedPreferenceListeners.clear();
	mListeners.clear();
	}

	/** This scope stores and retrieves settings from
	default preferences. */
	public static final String SCOPE_GLOBAL = "default_scope";

	/**
	* Returns the SharedPreferences file matching the scope
	* argument.
	*
	* Camera and module preferences files are cached,
	* until the camera id or module id changes, then the listeners
	* are unregistered and a new file is opened.
	*/
	private SharedPreferences getPreferencesFromScope(String scope) {
	if (scope.equals(SCOPE_GLOBAL)) {
	return mDefaultPreferences;
	}

	if (mCustomPreferences != null) {
	closePreferences(mCustomPreferences);
	}
	mCustomPreferences = openPreferences(scope);
	return mCustomPreferences;
	}

	/**
	* Set default and valid values for a setting, for a String default and
	* a set of String possible values that are already defined.
	* This is not required.
	*/
	public void setDefaults(String key, String defaultValue, String[] possibleValues) {
	mDefaultsStore.storeDefaults(key, defaultValue, possibleValues);
	}

	/**
	* Set default and valid values for a setting, for an Integer default and
	* a set of Integer possible values that are already defined.
	* This is not required.
	*/
	public void setDefaults(String key, int defaultValue, int[] possibleValues) {
	String defaultValueString = Integer.toString(defaultValue);
	String[] possibleValuesString = new String[possibleValues.length];
	for (int i = 0; i < possibleValues.length; i++) {
	possibleValuesString[i] = Integer.toString(possibleValues[i]);
	}
	mDefaultsStore.storeDefaults(key, defaultValueString, possibleValuesString);
	}

	/**
	* Set default and valid values for a setting, for a boolean default.
	* The set of boolean possible values is always { false, true }.
	* This is not required.
	*/
	public void setDefaults(String key, boolean defaultValue) {
	String defaultValueString = defaultValue ? "1" : "0";
	String[] possibleValues = { "0", "1" };
	mDefaultsStore.storeDefaults(key, defaultValueString, possibleValues);
	}

	/**
	* Retrieve a default from the DefaultsStore as a String.
	*/
	public String getStringDefault(String key) {
	return mDefaultsStore.getDefaultValue(key);
	}

	/**
	* Retrieve a default from the DefaultsStore as an Integer.
	*/
	public Integer getIntegerDefault(String key) {
	String defaultValueString = mDefaultsStore.getDefaultValue(key);
	return defaultValueString == null ? 0 : Integer.parseInt(defaultValueString);
	}

	/**
	* Retrieve a default from the DefaultsStore as a boolean.
	*/
	public boolean getBooleanDefault(String key) {
	String defaultValueString = mDefaultsStore.getDefaultValue(key);
	return defaultValueString == null ? false :
	(Integer.parseInt(defaultValueString) != 0);
	}

	/**
	* Retrieve a setting's value as a String, manually specifiying
	* a default value.
	*/
	public String getString(String scope, String key, String defaultValue) {
	SharedPreferences preferences = getPreferencesFromScope(scope);
	try {
	return preferences.getString(key, defaultValue);
	} catch (ClassCastException e) {
	Log.w(TAG, "existing preference with invalid type, removing and returning default", e);
	preferences.edit().remove(key).apply();
	return defaultValue;
	}
	}

	/**
	* Retrieve a setting's value as a String, using the default value
	* stored in the DefaultsStore.
	*/
	public String getString(String scope, String key) {
	return getString(scope, key, getStringDefault(key));
	}

	/**
	* Retrieve a setting's value as an Integer, manually specifying
	* a default value.
	*/
	public Integer getInteger(String scope, String key, Integer defaultValue) {
	String defaultValueString = Integer.toString(defaultValue);
	String value = getString(scope, key, defaultValueString);
	return convertToInt(value);
	}

	/**
	* Retrieve a setting's value as an Integer, converting the default value
	* stored in the DefaultsStore.
	*/
	public Integer getInteger(String scope, String key) {
	return getInteger(scope, key, getIntegerDefault(key));
	}

	/**
	* Retrieve a setting's value as a boolean, manually specifiying
	* a default value.
	*/
	public boolean getBoolean(String scope, String key, boolean defaultValue) {
	String defaultValueString = defaultValue ? "1" : "0";
	String value = getString(scope, key, defaultValueString);
	return convertToBoolean(value);
	}

	/**
	* Retrieve a setting's value as a boolean, converting the default value
	* stored in the DefaultsStore.
	*/
	public boolean getBoolean(String scope, String key) {
	return getBoolean(scope, key, getBooleanDefault(key));
	}

	/**
	* Retrieve a setting's value as a {@link Size}. Returns <code>null</code>
	* if value could not be parsed as a size.
	*/
	public Size getSize(String scope, String key) {
	String strValue = getString(scope, key);
	if (strValue == null) {
	return null;
	}

	String[] widthHeight = strValue.split("x");
	if (widthHeight.length != 2) {
	return null;
	}

	try {
	int width = Integer.parseInt(widthHeight[0]);
	int height = Integer.parseInt(widthHeight[1]);
	return new Size(width, height);
	} catch (NumberFormatException ex) {
	return null;
	}
	}

	/**
	* If possible values are stored for this key, return the
	* index into that list of the currently set value.
	*
	* For example, if a set of possible values is [2,3,5],
	* and the current value set of this key is 3, this method
	* returns 1.
	*
	* If possible values are not stored for this key, throw
	* an IllegalArgumentException.
	*/
	public int getIndexOfCurrentValue(String scope, String key) {
	String[] possibleValues = mDefaultsStore.getPossibleValues(key);
	if (possibleValues == null \|\| possibleValues.length == 0) {
	throw new IllegalArgumentException(
	"No possible values for scope=" + scope + " key=" + key);
	}

	String value = getString(scope, key);
	for (int i = 0; i < possibleValues.length; i++) {
	if (value.equals(possibleValues[i])) {
	return i;
	}
	}
	throw new IllegalStateException("Current value for scope=" + scope + " key="
	+ key + " not in list of possible values");
	}

	/**
	* Store a setting's value using a String value. No conversion
	* occurs before this value is stored in SharedPreferences.
	*/
	public void set(String scope, String key, String value) {
	SharedPreferences preferences = getPreferencesFromScope(scope);
	preferences.edit().putString(key, value).apply();
	}

	/**
	* Store a setting's value using an Integer value. Type conversion
	* to String occurs before this value is stored in SharedPreferences.
	*/
	public void set(String scope, String key, int value) {
	set(scope, key, convert(value));
	}

	/**
	* Store a setting's value using a boolean value. Type conversion
	* to an Integer and then to a String occurs before this value is
	* stored in SharedPreferences.
	*/
	public void set(String scope, String key, boolean value) {
	set(scope, key, convert(value));
	}

	/**
	* Set a setting to the default value stored in the DefaultsStore.
	*/
	public void setToDefault(String scope, String key) {
	set(scope, key, getStringDefault(key));
	}

	/**
	* If a set of possible values is defined, set the current value
	* of a setting to the possible value found at the given index.
	*
	* For example, if the possible values for a key are [2,3,5],
	* and the index given to this method is 2, then this method would
	* store the value 5 in SharedPreferences for the key.
	*
	* If the index is out of the bounds of the range of possible values,
	* or there are no possible values for this key, then this
	* method throws an exception.
	*/
	public void setValueByIndex(String scope, String key, int index) {
	String[] possibleValues = mDefaultsStore.getPossibleValues(key);
	if (possibleValues.length == 0) {
	throw new IllegalArgumentException(
	"No possible values for scope=" + scope + " key=" + key);
	}

	if (index >= 0 && index < possibleValues.length) {
	set(scope, key, possibleValues[index]);
	} else {
	throw new IndexOutOfBoundsException("For possible values of scope=" + scope
	+ " key=" + key);
	}
	}

	/**
	* Check that a setting has some value stored.
	*/
	public boolean isSet(String scope, String key) {
	SharedPreferences preferences = getPreferencesFromScope(scope);
	return preferences.contains(key);
	}

	/**
	* Check whether a settings's value is currently set to the
	* default value.
	*/
	public boolean isDefault(String scope, String key) {
	String defaultValue = getStringDefault(key);
	String value = getString(scope, key);
	return value == null ? false : value.equals(defaultValue);
	}

	/**
	* Remove a setting.
	*/
	public void remove(String scope, String key) {
	SharedPreferences preferences = getPreferencesFromScope(scope);
	preferences.edit().remove(key).apply();
	}

	/**
	* Package private conversion method to turn ints into preferred
	* String storage format.
	*
	* @param value int to be stored in Settings
	* @return String which represents the int
	*/
	static String convert(int value) {
	return Integer.toString(value);
	}

	/**
	* Package private conversion method to turn String storage format into
	* ints.
	*
	* @param value String to be converted to int
	* @return int value of stored String
	*/
	static int convertToInt(String value) {
	return Integer.parseInt(value);
	}

	/**
	* Package private conversion method to turn String storage format into
	* booleans.
	*
	* @param value String to be converted to boolean
	* @return boolean value of stored String
	*/
	static boolean convertToBoolean(String value) {
	return Integer.parseInt(value) != 0;
	}


	/**
	* Package private conversion method to turn booleans into preferred
	* String storage format.
	*
	* @param value boolean to be stored in Settings
	* @return String which represents the boolean
	*/
	static String convert(boolean value) {
	return value ? "1" : "0";
	}
	}