implement cloud settings backup

AndroidManifest.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.fox.ttrss"
-    android:versionCode="43"
-    android:versionName="0.3.10" >
+    android:versionCode="44"
+    android:versionName="0.3.11" >
 
     <uses-sdk android:minSdkVersion="7" />
 
@@ -11,6 +11,8 @@
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 
     <application
+        android:allowBackup="true"
+    	android:backupAgent="PrefsBackupAgent"
         android:hardwareAccelerated="true"
         android:icon="@drawable/icon"
         android:label="@string/app_name" >
@@ -43,6 +45,10 @@
         <activity
             android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"
             android:name="com.google.ads.AdActivity" />
+
+	<meta-data android:name="com.google.android.backup.api_key"
+    	    android:value="AEdPqrEAAAAIwG6zsGB4qo6ZhjfwIJpm9WI7AqmWaoRXm6ZJnA" />
+
     </application>
 
 </manifest>

src/org/fox/ttrss/PrefsBackupAgent.java

@@ -0,0 +1,19 @@
+package org.fox.ttrss;
+
+import android.app.backup.BackupAgentHelper;
+import android.app.backup.SharedPreferencesBackupHelper;
+
+public class PrefsBackupAgent extends BackupAgentHelper {
+	// The name of the SharedPreferences file
+    static final String PREFS = "org.fox.ttrss_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);
+    }
+}