/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.camera.settings;
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import android.content.SharedPreferences;
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import com.android.camera.debug.Log;
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/**
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* The SettingsUpgrader class can be used to define an upgrade flow that
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* executes upgrade logic to a target version when a version number has changed.
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*/
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public abstract class SettingsUpgrader {
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private static final Log.Tag TAG = new Log.Tag("SettingsUpgrader");
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private final String mVersionKey;
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private final int mTargetVersion;
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// These values were in use by the original preferences management, before
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// SettingsManager, to represent string-based booleans via typed string
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// resource arrays. We no longer utilize such value arrays, and reference
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// these constants only within SettingsUpgraders to convert to new string-
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// based booleans.
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protected static final String OLD_SETTINGS_VALUE_NONE = "none";
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protected static final String OLD_SETTINGS_VALUE_ON = "on";
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protected static final String OLD_SETTINGS_VALUE_OFF = "off";
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public SettingsUpgrader(String versionKey, int targetVersion) {
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mVersionKey = versionKey;
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mTargetVersion = targetVersion;
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}
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/**
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* Execute an upgrade callback if an upgrade version has changed. Third
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* party modules also use this to upgrade settings local to them.
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*/
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public void upgrade(SettingsManager settingsManager) {
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int lastVersion = getLastVersion(settingsManager);
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if (lastVersion != mTargetVersion) {
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upgrade(settingsManager, lastVersion, mTargetVersion);
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}
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settingsManager.set(SettingsManager.SCOPE_GLOBAL, mVersionKey, mTargetVersion);
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}
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/**
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* Perform upgrades to bring any settings up to date to the version
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* specified in currentVersion, where the settings were last upgraded to
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* lastVersion. Typically an Upgrader will check whether lastVersion is less
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* than some known version for a particular setting, and apply upgrade logic
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* if lastVersion is less than that known version.
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*/
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protected abstract void upgrade(SettingsManager settingsManager, int lastVersion,
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int targetVersion);
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/**
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* Retrieve the last persisted version for the particular upgrader.
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* Typically will be stored in SCOPE_GLOBAL in SettingsManager, but an
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* Upgrader may need to perform an upgrade analysis on the version
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* persistence itself and should do so here.
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*
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* @throws a {@link ClassCastException} if the value for Version is not a
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* String
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*/
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protected int getLastVersion(SettingsManager settingsManager) {
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return settingsManager.getInteger(SettingsManager.SCOPE_GLOBAL, mVersionKey);
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}
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/**
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* A helper function that is used to remove a setting stored as a boolean,
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* and return the value that was removed.
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* <p>
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* This is used in the upgrade path to change all underlying
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* SharedPreferences values to Strings. It can be used by third party
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* modules to upgrade their boolean settings to Strings.
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*/
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protected boolean removeBoolean(SharedPreferences oldPreferencesLocation, String key) {
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boolean value = false;
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try {
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value = oldPreferencesLocation.getBoolean(key, value);
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} catch (ClassCastException e) {
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Log.e(TAG, "error reading old value, removing and returning default", e);
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}
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oldPreferencesLocation.edit().remove(key).apply();
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return value;
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}
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/**
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* A helper function that is used to remove a setting stored as an Integer,
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* and return the value that was removed.
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* <p>
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* This is used in the upgrade path to change all underlying
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* SharedPreferences values to Strings. It can be used by third party
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* modules to upgrade their Integer settings to Strings.
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*/
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protected int removeInteger(SharedPreferences oldPreferencesLocation, String key) {
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int value = 0;
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try {
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value = oldPreferencesLocation.getInt(key, value);
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} catch (ClassCastException e) {
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Log.e(TAG, "error reading old value, removing and returning default", e);
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}
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oldPreferencesLocation.edit().remove(key).apply();
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return value;
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}
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/**
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* A helper function that is used to remove a setting stored as a String,
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* and return the value that was removed.
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* <p>
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* This is used in the upgrade path to change all underlying
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* SharedPreferences values to Strings. It can be used by third party
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* modules to upgrade their boolean settings to Strings.
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*/
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protected String removeString(SharedPreferences oldPreferencesLocation, String key) {
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String value = null;
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try {
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value = oldPreferencesLocation.getString(key, value);
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} catch (ClassCastException e) {
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Log.e(TAG, "error reading old value, removing and returning default", e);
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}
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oldPreferencesLocation.edit().remove(key).apply();
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return value;
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}
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}
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