Android Data Backup And Restore Complete Guide

Step 1: Set Up Your Android Project

First, create a new Android project in Android Studio. If you already have a project, ensure it targets API level 23 or above.

Step 2: Enable Google Play Services

Auto Backup requires that your app be published (or at least signed) under a developer account and uses Google Play services. In your build.gradle (Module: app), make sure you have the following dependencies:

dependencies {
    // Other dependencies
    implementation 'com.google.android.gms:play-services-auth:20.4.1'
}

Step 3: Modify build.gradle to Enable Auto Backup

In your build.gradle file, enable Auto Backup by adding the backup block to your defaultConfig.

android {
    // Other configurations
    defaultConfig {
        applicationId "com.example.yourapp"
        minSdkVersion 23
        targetSdkVersion 31  // Make sure this is at least 23
        versionCode 1
        versionName "1.0"

        // Add this block to enable auto backup
        backup {
            rules {
                exclude "**/shared_prefs/your_excluded_prefs.xml"
                include "**/*"
            }
        }
    }
}

Step 4: Define BackupAgent

To handle more complex backup scenarios, you might need to define a custom BackupAgent. For this example, we're using Auto Backup, so this step isn't necessary. However, if you do need it, here's how you can do it:

Create a new Java class extending FileBackupHelper or SharedPreferencesBackupHelper, depending on what you need to back up.

// CustomBackupAgent.java
import android.app.backup.FileBackupHelper;
import android.app.backup.BackupAgentHelper;
import android.os.ParcelFileDescriptor;

public class CustomBackupAgent extends BackupAgentHelper {
    static final String FILES_BACKUP_KEY = "yourfiles";

    @Override
    public void onCreate() {
        FileBackupHelper helper = new FileBackupHelper(this, "yourfile.dat");
        addHelper(FILES_BACKUP_KEY, helper);
    }
}

Then, declare your BackupAgent in the AndroidManifest.xml.

<application ... >
    <agent
        android:name=".CustomBackupAgent"
        android:label="@string/app_name"/>
</application>

Step 5: Test Your Backup

Since Auto Backup uses Google’s servers, testing it is a bit different. You can use the Android Debug Bridge (ADB) to trigger backup and restore manually for testing purposes.

Enable Debugging: Ensure adb debugging is enabled in your device or emulator.

Backup Trigger Command:

adb shell bmgr backupnow -f com.example.yourapp

Restore Trigger Command:

1. Uninstall the app.
2. Install the app again.
3. Run the following command:

adb shell bmgr restore com.example.yourapp com.example.yourapp

This will simulate the entire process of backup and restore for your app.

Complete Example

Here’s a quick wrap-up with all the steps combined for a simple shared preference backup:

AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.yourapp">

    <application
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme"
        android:allowBackup="true">
        
        <!-- Declare Backup Rule if a custom BackupAgent is created -->
        <meta-data
            android:name="com.google.android.backup.api_key"
            android:value="YOUR_API_KEY"/>

        <!-- Uncomment this section if you use a custom BackupAgent -->
        <!--
        <service 
            android:name=".CustomBackupAgent"
            android:permission="android.permission.BIND_APPWIDGET">
            <intent-filter>
                <action android:name="android.app.backup.BackupService" />
            </intent-filter>
        </service>
        -->

    </application>

</manifest>

build.gradle (App Level)

android {
    compileSdkVersion 31

    defaultConfig {
        applicationId "com.example.yourapp"
        minSdkVersion 23
        targetSdkVersion 31
        versionCode 1
        versionName "1.0"

        backup {
            rules {
                exclude "**/shared_prefs/your_excluded_prefs.xml"
                include "**/*"
            }
        }
    }

    // Other configurations like dependencies...
}

dependencies {
    implementation 'com.google.android.gms:play-services-auth:20.4.1'
    // Other dependencies
}

Using Shared Preferences Normally

No changes are required for backing up shared preferences as Auto Backup automatically backs them up.

// MainActivity.java
import android.content.SharedPreferences;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private SharedPreferences sharedPreferences;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        sharedPreferences = getSharedPreferences("your_prefs", MODE_PRIVATE);

        // Example usage
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putString("key", "value");
        editor.apply();

        String value = sharedPreferences.getString("key", "default value");

        // Do something with the value here...
    }
}

Step 6: Handle Backups Manually (Optional)

If you need to control backup and restore more strictly, you can define a custom BackupAgent as shown above. For instance, you might want to include some files but exclude others.

// CustomBackupAgent.java
import android.app.backup.FileBackupHelper;
import android.app.backup.BackupAgentHelper;
import android.os.ParcelFileDescriptor;

public class CustomBackupAgent extends BackupAgentHelper {
    static final String PREFS_BACKUP_KEY = "myprefs";
    static final String DB_BACKUP_KEY = "mydb";

    @Override
    public void onCreate() {
        SharedPreferencesBackupHelper prefsHelper = new SharedPreferencesBackupHelper(this, "your_prefs");
        addHelper(PREFS_BACKUP_KEY, prefsHelper);

        FileBackupHelper dbHelper = new FileBackupHelper(this, "database.db");
        addHelper(DB_BACKUP_KEY, dbHelper);
    }
}

Declare the service in AndroidManifest.xml:

<service 
    android:name=".CustomBackupAgent"
    android:exported="true"
    android:permission="android.permission.BIND_BACKUP_AGENT">
    <intent-filter>
        <action android:name="android.app.backup.BBackupService" />
    </intent-filter>
</service>

Summary

1. Set up your Android project
2. Add Google Play services dependency
3. Modify build.gradle for Auto Backup
4. Define custom BackupAgent if needed
5. Test using ADB commands
6. Use Shared Preferences normally for automatic backup

By following these steps, you should be able to implement and test basic backup and restore functionality in your Android app. If you need more advanced features, refer to the Android documentation on Backup and Restore.