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/*
* Copyright (C) 2014 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.SharedPreferences;
import com.android.camera.debug.Log;
/**
* The SettingsUpgrader class can be used to define an upgrade flow that
* executes upgrade logic to a target version when a version number has changed.
*/
public abstract class SettingsUpgrader {
private static final Log.Tag TAG = new Log.Tag("SettingsUpgrader");
private final String mVersionKey;
private final int mTargetVersion;
// These values were in use by the original preferences management, before
// SettingsManager, to represent string-based booleans via typed string
// resource arrays. We no longer utilize such value arrays, and reference
// these constants only within SettingsUpgraders to convert to new string-
// based booleans.
protected static final String OLD_SETTINGS_VALUE_NONE = "none";
protected static final String OLD_SETTINGS_VALUE_ON = "on";
protected static final String OLD_SETTINGS_VALUE_OFF = "off";
public SettingsUpgrader(String versionKey, int targetVersion) {
mVersionKey = versionKey;
mTargetVersion = targetVersion;
}
/**
* Execute an upgrade callback if an upgrade version has changed. Third
* party modules also use this to upgrade settings local to them.
*/
public void upgrade(SettingsManager settingsManager) {
int lastVersion = getLastVersion(settingsManager);
if (lastVersion != mTargetVersion) {
upgrade(settingsManager, lastVersion, mTargetVersion);
}
settingsManager.set(SettingsManager.SCOPE_GLOBAL, mVersionKey, mTargetVersion);
}
/**
* Perform upgrades to bring any settings up to date to the version
* specified in currentVersion, where the settings were last upgraded to
* lastVersion. Typically an Upgrader will check whether lastVersion is less
* than some known version for a particular setting, and apply upgrade logic
* if lastVersion is less than that known version.
*/
protected abstract void upgrade(SettingsManager settingsManager, int lastVersion,
int targetVersion);
/**
* Retrieve the last persisted version for the particular upgrader.
* Typically will be stored in SCOPE_GLOBAL in SettingsManager, but an
* Upgrader may need to perform an upgrade analysis on the version
* persistence itself and should do so here.
*
* @throws a {@link ClassCastException} if the value for Version is not a
* String
*/
protected int getLastVersion(SettingsManager settingsManager) {
return settingsManager.getInteger(SettingsManager.SCOPE_GLOBAL, mVersionKey);
}
/**
* A helper function that is used to remove a setting stored as a boolean,
* and return the value that was removed.
* <p>
* This is used in the upgrade path to change all underlying
* SharedPreferences values to Strings. It can be used by third party
* modules to upgrade their boolean settings to Strings.
*/
protected boolean removeBoolean(SharedPreferences oldPreferencesLocation, String key) {
boolean value = false;
try {
value = oldPreferencesLocation.getBoolean(key, value);
} catch (ClassCastException e) {
Log.e(TAG, "error reading old value, removing and returning default", e);
}
oldPreferencesLocation.edit().remove(key).apply();
return value;
}
/**
* A helper function that is used to remove a setting stored as an Integer,
* and return the value that was removed.
* <p>
* This is used in the upgrade path to change all underlying
* SharedPreferences values to Strings. It can be used by third party
* modules to upgrade their Integer settings to Strings.
*/
protected int removeInteger(SharedPreferences oldPreferencesLocation, String key) {
int value = 0;
try {
value = oldPreferencesLocation.getInt(key, value);
} catch (ClassCastException e) {
Log.e(TAG, "error reading old value, removing and returning default", e);
}
oldPreferencesLocation.edit().remove(key).apply();
return value;
}
/**
* A helper function that is used to remove a setting stored as a String,
* and return the value that was removed.
* <p>
* This is used in the upgrade path to change all underlying
* SharedPreferences values to Strings. It can be used by third party
* modules to upgrade their boolean settings to Strings.
*/
protected String removeString(SharedPreferences oldPreferencesLocation, String key) {
String value = null;
try {
value = oldPreferencesLocation.getString(key, value);
} catch (ClassCastException e) {
Log.e(TAG, "error reading old value, removing and returning default", e);
}
oldPreferencesLocation.edit().remove(key).apply();
return value;
}
}
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