Update Flower Android Version

examples/android/README.md

@@ -1,12 +1,14 @@
 # Flower Android Example (TensorFlowLite)
 
-This example demonstrates a federated learning setup with Android Clients. The training on Android is done on a CIFAR10 dataset using TensorFlow Lite. The setup is as follows:
+This example demonstrates a federated learning setup with Android clients in a background thread. The training on Android is done on a CIFAR10 dataset using TensorFlow Lite. The setup is as follows:
 
 - The CIFAR10 dataset is randomly split across 10 clients. Each Android client holds a local dataset of 5000 training examples and 1000 test examples.
 - The FL server runs in Python but all the clients run on Android.
 - We use a strategy called FedAvgAndroid for this example.
 - The strategy is vanilla FedAvg with a custom serialization and deserialization to handle the Bytebuffers sent from Android clients to Python server.
 
+The background thread is established via the `WorkManager` library of Android, thus, it will run comfortably on Android Versions from 8 to 13.
+
 ## Project Setup
 
 Start by cloning the example project. We prepared a single-line command that you can copy into your shell which will checkout the example for you:

examples/android/client/app/src/main/AndroidManifest.xml

@@ -1,8 +1,16 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android">
-
-    <uses-permission android:name="android.permission.INTERNET" />
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
+    <uses-permission android:name="android.permission.RETRIEVE_TASKS" />
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission
+        android:name="android.permission.READ_EXTERNAL_STORAGE"/>
+    <uses-permission
+        android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
 
     <application
         android:allowBackup="true"
@@ -22,6 +30,28 @@
         <meta-data
             android:name="preloaded_fonts"
             android:resource="@array/preloaded_fonts" />
-    </application>
 
+        <service android:name=".FlowerWorker"
+            android:exported="false"
+            android:permission="android.permission.BIND_JOB_SERVICE" />
+
+        <service
+            android:name="androidx.work.impl.foreground.SystemForegroundService"
+            android:foregroundServiceType="dataSync"
+            tools:node="merge" />
+
+        <provider
+            android:name="androidx.startup.InitializationProvider"
+            android:authorities="${applicationId}.androidx-startup"
+            android:exported="false"
+            tools:node="merge">
+
+        </provider>
+
+        <meta-data
+            android:name="androidx.work.impl.WorkManagerInitializer"
+            android:value="androidx.startup"
+            tools:node="remove" />
+
+    </application>
 </manifest>

examples/android/client/app/src/main/java/flwr/android_client/FlowerClient.java

@@ -11,6 +11,8 @@
 import androidx.lifecycle.MutableLiveData;
 
 import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileWriter;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.nio.ByteBuffer;
@@ -64,6 +66,7 @@ public void setLastLoss(int epoch, float newLoss) {
 
     public void loadData(int device_id) {
         try {
+            Log.d("FLOWERCLIENT_LOAD", "loadData: ");
             BufferedReader reader = new BufferedReader(new InputStreamReader(this.context.getAssets().open("data/partition_" + (device_id - 1) + "_train.txt")));
             String line;
             int i = 0;
@@ -137,4 +140,38 @@ private static float[] prepareImage(Bitmap bitmap)  {
 
         return normalizedRgb;
     }
-}
+
+    // function to write to a file :
+
+    public void writeStringToFile( Context context , String fileName, String content) {
+        try {
+            // Get the app-specific external storage directory
+            File directory = context.getExternalFilesDir(null);
+
+            if (directory != null) {
+                File file = new File(directory, fileName);
+
+                // Check if the file exists
+                boolean fileExists = file.exists();
+
+                // Open a FileWriter in append mode
+                FileWriter writer = new FileWriter(file, true);
+
+                // If the file exists and is not empty, add a new line
+                if (fileExists && file.length() > 0) {
+                    writer.append("\n");
+                }
+
+                // Write the string to the file
+                writer.append(content);
+
+                // Close the FileWriter
+                writer.close();
+            }
+        } catch (IOException e) {
+            e.printStackTrace(); // Handle the exception as needed
+        }
+    }
+
+
+}