在Android中备份SharedPreferences?
我想在SharedPreferences中备份一个值,以便我可以在重新安装后读出这个值。
我的代码不起作用,我不知道错误是什么。
MyBackupAgent
package com.app.appname; import android.app.backup.BackupAgentHelper; import android.app.backup.BackupManager; import android.app.backup.SharedPreferencesBackupHelper; import android.content.Context; public class MyBackupAgent extends BackupAgentHelper{ static final String PREFS_DISPLAY = "AppName"; private Context context; static final String MY_PREFS_BACKUP_KEY = "keyToStore"; public MyBackupAgent(Context context){ this.context = context; SharedPreferencesBackupHelper helper = new SharedPreferencesBackupHelper(context, PREFS_DISPLAY); addHelper(MY_PREFS_BACKUP_KEY, helper); } public void storeData(){ BackupManager backupManager = new BackupManager(context); backupManager.dataChanged(); } }
我如何存储数据:
... SharedPreferences settings = getSharedPreferences("AppName", 0); SharedPreferences.Editor editor = settings.edit(); editor.putBoolean("keyToStore", true); editor.commit(); new MyBackupAgent(this).storeData(); ...
我如何收到数据:
... SharedPreferences settings = getSharedPreferences("AppName", 0); boolean value = settings.getBoolean("keyToStore", false); ...
我还在Android Manifest中添加了API:
你知道我做错了什么以及它是如何工作的吗? 它真的有效吗?
您的SharedPreferences备份代理类应该是这样的:
public class MyPrefsBackupAgent extends BackupAgentHelper { // The name of the SharedPreferences file static final String PREFS = "user_preferences"; // A key to uniquely identify the set of backup data static final String PREFS_BACKUP_KEY = "prefs"; // Allocate a helper and add it to the backup agent @Override public void onCreate() { SharedPreferencesBackupHelper helper = new SharedPreferencesBackupHelper(this, PREFS); addHelper(PREFS_BACKUP_KEY, helper); } }
然后,您必须使用以下内容请求云备份(它将完成异步):
import android.app.backup.BackupManager; ... public void requestBackup() { BackupManager bm = new BackupManager(this); bm.dataChanged(); }
并且您不需要手动还原SharedPreferences,因为它们由SharedPreferencesBackupHelper
类自动管理。
除了备份API密钥之外,不要忘记在清单中添加备份代理类:
有关这一切的更多信息,请访问http://developer.android.com/guide/topics/data/backup.html和http://developer.android.com/training/cloudsync/backupapi.html