Split-off MonitorService

Same motivation as for the parent device:
The monitor activity will be quickly destroyed,
unless it is connected to a foreground service.

By moving the thread and audio listener to a service,
this should be avoided.

app/src/main/AndroidManifest.xml

@@ -26,10 +26,15 @@
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:theme="@android:style/Theme.Holo">
+
         <service
             android:name=".ListenService"
             android:enabled="true"
             android:exported="false"/>
+        <service
+            android:name=".MonitorService"
+            android:enabled="true"
+            android:exported="false"/>
 
         <activity
             android:name=".StartActivity"
@@ -55,5 +60,4 @@
             android:configChanges="orientation|screenSize"
             android:parentActivityName=".DiscoverActivity" />
     </application>
-
 </manifest>

app/src/main/java/de/rochefort/childmonitor/MonitorActivity.java

@@ -1,159 +1,76 @@
 /*
  * This file is part of Child Monitor.
- *
+ * <p>
  * Child Monitor is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 3 of the License, or
  * (at your option) any later version.
- *
+ * <p>
  * Child Monitor is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU General Public License for more details.
- *
+ * <p>
  * You should have received a copy of the GNU General Public License
  * along with Child Monitor. If not, see <http://www.gnu.org/licenses/>.
  */
 package de.rochefort.childmonitor;
 
-import static de.rochefort.childmonitor.AudioCodecDefines.CODEC;
-
 import android.app.Activity;
+import android.content.ComponentName;
 import android.content.Context;
-import android.media.AudioRecord;
+import android.content.Intent;
-import android.media.MediaRecorder;
+import android.content.ServiceConnection;
 import android.net.ConnectivityManager;
 import android.net.LinkAddress;
 import android.net.Network;
 import android.net.NetworkInfo;
-import android.net.nsd.NsdManager;
-import android.net.nsd.NsdServiceInfo;
-import android.os.Build;
 import android.os.Bundle;
+import android.os.IBinder;
+import android.support.v4.content.ContextCompat;
 import android.util.Log;
 import android.widget.TextView;
 
-import java.io.IOException;
-import java.io.OutputStream;
 import java.net.InetAddress;
-import java.net.ServerSocket;
-import java.net.Socket;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Objects;
 
 public class MonitorActivity extends Activity {
     final static String TAG = "ChildMonitor";
-
+    private final ServiceConnection connection = new ServiceConnection() {
-    private NsdManager nsdManager;
+        public void onServiceConnected(ComponentName className, IBinder service) {
-
+            // This is called when the connection with the service has been
-    private NsdManager.RegistrationListener registrationListener;
+            // established, giving us the service object we can use to
-
+            // interact with the service.  Because we have bound to a explicit
-    private ServerSocket currentSocket;
+            // service that we know is running in our own process, we can
-
+            // cast its IBinder to a concrete class and directly access it.
-    private Object connectionToken;
+            MonitorService bs = ((MonitorService.MonitorBinder) service).getService();
-
+            bs.setMonitorActivity(MonitorActivity.this);
-    private int currentPort;
-
-    private void serviceConnection(Socket socket) {
-            runOnUiThread(() -> {
-                final TextView statusText = findViewById(R.id.textStatus);
-                statusText.setText(R.string.streaming);
-            });
-
-            final int frequency = AudioCodecDefines.FREQUENCY;
-            final int channelConfiguration = AudioCodecDefines.CHANNEL_CONFIGURATION_IN;
-            final int audioEncoding = AudioCodecDefines.ENCODING;
-
-            final int bufferSize = AudioRecord.getMinBufferSize(frequency, channelConfiguration, audioEncoding);
-        final AudioRecord audioRecord;
-        try {
-            audioRecord = new AudioRecord(
-                    MediaRecorder.AudioSource.MIC,
-                    frequency,
-                    channelConfiguration,
-                    audioEncoding,
-                    bufferSize
-            );
-        } catch (SecurityException e) {
-            // This should never happen, we asked for permission before
-            throw new RuntimeException(e);
         }
 
-        final int pcmBufferSize = bufferSize*2;
+        public void onServiceDisconnected(ComponentName className) {
-            final short[] pcmBuffer = new short[pcmBufferSize];
+            // This is called when the connection with the service has been
-            final byte[] ulawBuffer = new byte[pcmBufferSize];
+            // unexpectedly disconnected -- that is, its process crashed.
-
+            // Because it is running in our same process, we should never
-            try {
+            // see this happen.
-                audioRecord.startRecording();
-                final OutputStream out = socket.getOutputStream();
-
-                socket.setSendBufferSize(pcmBufferSize);
-                Log.d(TAG, "Socket send buffer size: " + socket.getSendBufferSize());
-
-                while (socket.isConnected() && currentSocket != null && !Thread.currentThread().isInterrupted()) {
-                    final int read = audioRecord.read(pcmBuffer, 0, bufferSize);
-                    int encoded = CODEC.encode(pcmBuffer, read, ulawBuffer, 0);
-                    out.write(ulawBuffer, 0, encoded);
         }
-            } catch (Exception e) {
+    };
-                Log.e(TAG, "Connection failed", e);
+    private boolean shouldUnbind;
-            } finally {
-                audioRecord.stop();
-            }
-    }
-
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         Log.i(TAG, "ChildMonitor start");
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_monitor);
-
-        nsdManager = (NsdManager)this.getSystemService(Context.NSD_SERVICE);
-        currentPort = 10000;
-        currentSocket = null;
-        final Object currentToken = new Object();
-        connectionToken = currentToken;
-
-        new Thread(() -> {
-            while(Objects.equals(connectionToken, currentToken)) {
-                try (ServerSocket serverSocket = new ServerSocket(currentPort)) {
-                    currentSocket = serverSocket;
-                    // Store the chosen port.
-                    final int localPort = serverSocket.getLocalPort();
-
-                    // Register the service so that parent devices can
-                    // locate the child device
-                    registerService(localPort);
-
-                    // Wait for a parent to find us and connect
-                    try (Socket socket = serverSocket.accept()) {
-                        Log.i(TAG, "Connection from parent device received");
-
-                        // We now have a client connection.
-                        // Unregister so no other clients will
-                        // attempt to connect
-                        unregisterService();
-                        serviceConnection(socket);
-                    }
-                } catch(Exception e) {
-                    // Just in case
-                    currentPort++;
-                    Log.e(TAG, "Failed to open server socket. Port increased to " + currentPort, e);
-                }
-            }
-        }).start();
-
         final TextView addressText = findViewById(R.id.address);
 
         List<String> listenAddresses = getListenAddresses();
-        if(!listenAddresses.isEmpty()) {
+        if (!listenAddresses.isEmpty()) {
             StringBuilder sb = new StringBuilder();
             for (int i = 0; i < listenAddresses.size(); i++) {
                 String listenAddress = listenAddresses.get(i);
                 sb.append(listenAddress);
-                if (i != listenAddresses.size() -1) {
+                if (i != listenAddresses.size() - 1) {
                     sb.append("\n\n");
                 }
             }
@@ -162,10 +79,11 @@ public class MonitorActivity extends Activity {
             addressText.setText(R.string.notConnected);
         }
 
+        ensureServiceRunningAndBind();
     }
 
     private List<String> getListenAddresses() {
-        ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
+        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
         List<String> listenAddresses = new ArrayList<>();
         if (cm != null) {
             for (Network network : cm.getAllNetworks()) {
@@ -186,87 +104,37 @@ public class MonitorActivity extends Activity {
     }
 
     @Override
-    protected void onStop() {
+    public void onDestroy() {
-        Log.i(TAG, "ChildMonitor stop");
+        doUnbindAndStopService();
-
+        super.onDestroy();
-        unregisterService();
-
-        connectionToken = null;
-        if(currentSocket != null) {
-            try {
-                currentSocket.close();
-                currentSocket = null;
-            } catch (IOException e) {
-                Log.e(TAG, "Failed to close active socket on port "+currentPort);
-            }
-        }
-        super.onStop();
     }
 
-    private void registerService(final int port) {
+    void ensureServiceRunningAndBind() {
-        final NsdServiceInfo serviceInfo  = new NsdServiceInfo();
+        final Context context = this;
-        serviceInfo.setServiceName("ChildMonitor on " + Build.MODEL);
+        final Intent intent = new Intent(context, MonitorService.class);
-        serviceInfo.setServiceType("_childmonitor._tcp.");
+        ContextCompat.startForegroundService(context, intent);
-        serviceInfo.setPort(port);
+        // Attempts to establish a connection with the service.  We use an
-
+        // explicit class name because we want a specific service
-        registrationListener = new NsdManager.RegistrationListener() {
+        // implementation that we know will be running in our own process
-            @Override
+        // (and thus won't be supporting component replacement by other
-            public void onServiceRegistered(NsdServiceInfo nsdServiceInfo) {
+        // applications).
-                // Save the service name.  Android may have changed it in order to
+        if (bindService(intent, connection, Context.BIND_AUTO_CREATE)) {
-                // resolve a conflict, so update the name you initially requested
+            shouldUnbind = true;
-                // with the name Android actually used.
+            Log.i(TAG, "Bound service");
-                final String serviceName = nsdServiceInfo.getServiceName();
+        } else {
-
+            Log.e(TAG, "Error: The requested service doesn't " +
-                Log.i(TAG, "Service name: " + serviceName);
+                    "exist, or this client isn't allowed access to it.");
-
+        }
-                MonitorActivity.this.runOnUiThread(() -> {
-                    final TextView statusText = findViewById(R.id.textStatus);
-                    statusText.setText(R.string.waitingForParent);
-
-                    final TextView serviceText = findViewById(R.id.textService);
-                    serviceText.setText(serviceName);
-
-                    final TextView portText = findViewById(R.id.port);
-                    portText.setText(Integer.toString(port));
-                });
     }
 
-            @Override
+    void doUnbindAndStopService() {
-            public void onRegistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
+        if (shouldUnbind) {
-                // Registration failed!  Put debugging code here to determine why.
+            // Release information about the service's state.
-                Log.e(TAG, "Registration failed: " + errorCode);
+            unbindService(connection);
-            }
+            shouldUnbind = false;
-
-            @Override
-            public void onServiceUnregistered(NsdServiceInfo arg0) {
-                // Service has been unregistered.  This only happens when you call
-                // NsdManager.unregisterService() and pass in this listener.
-
-                Log.i(TAG, "Unregistering service");
-            }
-
-            @Override
-            public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
-                // Unregistration failed.  Put debugging code here to determine why.
-
-                Log.e(TAG, "Unregistration failed: " + errorCode);
-            }
-        };
-
-        nsdManager.registerService(
-                serviceInfo, NsdManager.PROTOCOL_DNS_SD, registrationListener);
-    }
-
-    /**
-     * Uhregistered the service and assigns the listener
-     * to null.
-     */
-    private void unregisterService() {
-        if(registrationListener != null) {
-            Log.i(TAG, "Unregistering monitoring service");
-
-            nsdManager.unregisterService(registrationListener);
-            registrationListener = null;
         }
+        final Context context = this;
+        final Intent intent = new Intent(context, MonitorService.class);
+        context.stopService(intent);
     }
 }

app/src/main/java/de/rochefort/childmonitor/MonitorService.java

@@ -0,0 +1,314 @@
+/**
+ * This file is part of Child Monitor.
+ * <p>
+ * Child Monitor is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * <p>
+ * Child Monitor is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ * <p>
+ * You should have received a copy of the GNU General Public License
+ * along with Child Monitor. If not, see <http://www.gnu.org/licenses/>.
+ */
+package de.rochefort.childmonitor;
+
+import static de.rochefort.childmonitor.AudioCodecDefines.CODEC;
+
+import android.app.Notification;
+import android.app.NotificationChannel;
+import android.app.NotificationManager;
+import android.app.PendingIntent;
+import android.app.Service;
+import android.content.Context;
+import android.content.Intent;
+import android.media.AudioRecord;
+import android.media.MediaRecorder;
+import android.net.nsd.NsdManager;
+import android.net.nsd.NsdServiceInfo;
+import android.os.Binder;
+import android.os.Build;
+import android.os.IBinder;
+import android.support.v4.app.NotificationCompat;
+import android.util.Log;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.util.Objects;
+
+public class MonitorService extends Service {
+    final static String TAG = "MonitorService";
+    final static String CHANNEL_ID = TAG;
+    public static final int ID = 1338;
+    private final IBinder binder = new MonitorBinder();
+    private NsdManager nsdManager;
+    private NsdManager.RegistrationListener registrationListener;
+    private ServerSocket currentSocket;
+    private Object connectionToken;
+    private int currentPort;
+    private NotificationManager notificationManager;
+    private Thread monitorThread;
+    private MonitorActivity monitorActivity;
+
+    public void setMonitorActivity(MonitorActivity monitorActivity) {
+        this.monitorActivity = monitorActivity;
+    }
+
+    private void serviceConnection(Socket socket) {
+        final MonitorActivity ma = monitorActivity;
+        if (ma != null) {
+            ma.runOnUiThread(() -> {
+                final TextView statusText = monitorActivity.findViewById(R.id.textStatus);
+                statusText.setText(R.string.streaming);
+            });
+        }
+
+        final int frequency = AudioCodecDefines.FREQUENCY;
+        final int channelConfiguration = AudioCodecDefines.CHANNEL_CONFIGURATION_IN;
+        final int audioEncoding = AudioCodecDefines.ENCODING;
+
+        final int bufferSize = AudioRecord.getMinBufferSize(frequency, channelConfiguration, audioEncoding);
+        final AudioRecord audioRecord;
+        try {
+            audioRecord = new AudioRecord(
+                    MediaRecorder.AudioSource.MIC,
+                    frequency,
+                    channelConfiguration,
+                    audioEncoding,
+                    bufferSize
+            );
+        } catch (SecurityException e) {
+            // This should never happen, we asked for permission before
+            throw new RuntimeException(e);
+        }
+
+        final int pcmBufferSize = bufferSize * 2;
+        final short[] pcmBuffer = new short[pcmBufferSize];
+        final byte[] ulawBuffer = new byte[pcmBufferSize];
+
+        try {
+            audioRecord.startRecording();
+            final OutputStream out = socket.getOutputStream();
+
+            socket.setSendBufferSize(pcmBufferSize);
+            Log.d(TAG, "Socket send buffer size: " + socket.getSendBufferSize());
+
+            while (socket.isConnected() && currentSocket != null && !Thread.currentThread().isInterrupted()) {
+                final int read = audioRecord.read(pcmBuffer, 0, bufferSize);
+                int encoded = CODEC.encode(pcmBuffer, read, ulawBuffer, 0);
+                out.write(ulawBuffer, 0, encoded);
+            }
+        } catch (Exception e) {
+            Log.e(TAG, "Connection failed", e);
+        } finally {
+            audioRecord.stop();
+        }
+    }
+
+
+    @Override
+    public void onCreate() {
+        Log.i(TAG, "ChildMonitor start");
+        super.onCreate();
+        notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
+
+        nsdManager = (NsdManager) this.getSystemService(Context.NSD_SERVICE);
+        currentPort = 10000;
+        currentSocket = null;
+    }
+
+    @Override
+    public int onStartCommand(Intent intent, int flags, int startId) {
+        Log.i(TAG, "Received start id " + startId + ": " + intent);
+        // Display a notification about us starting.  We put an icon in the status bar.
+        createNotificationChannel();
+        Notification n = buildNotification();
+        startForeground(ID, n);
+        ensureMonitorThread();
+
+        return START_REDELIVER_INTENT;
+    }
+
+    private void ensureMonitorThread() {
+        Thread mt = monitorThread;
+        if (mt != null && mt.isAlive()) {
+            return;
+        }
+
+        final Object currentToken = new Object();
+        connectionToken = currentToken;
+
+        monitorThread = new Thread(() -> {
+            while (Objects.equals(connectionToken, currentToken)) {
+                try (ServerSocket serverSocket = new ServerSocket(currentPort)) {
+                    currentSocket = serverSocket;
+                    // Store the chosen port.
+                    final int localPort = serverSocket.getLocalPort();
+
+                    // Register the service so that parent devices can
+                    // locate the child device
+                    registerService(localPort);
+
+                    // Wait for a parent to find us and connect
+                    try (Socket socket = serverSocket.accept()) {
+                        Log.i(TAG, "Connection from parent device received");
+
+                        // We now have a client connection.
+                        // Unregister so no other clients will
+                        // attempt to connect
+                        unregisterService();
+                        serviceConnection(socket);
+                    }
+                } catch (Exception e) {
+                    // Just in case
+                    currentPort++;
+                    Log.e(TAG, "Failed to open server socket. Port increased to " + currentPort, e);
+                }
+            }
+        });
+        monitorThread.start();
+    }
+
+    private void registerService(final int port) {
+        final NsdServiceInfo serviceInfo = new NsdServiceInfo();
+        serviceInfo.setServiceName("ChildMonitor on " + Build.MODEL);
+        serviceInfo.setServiceType("_childmonitor._tcp.");
+        serviceInfo.setPort(port);
+
+        registrationListener = new NsdManager.RegistrationListener() {
+            @Override
+            public void onServiceRegistered(NsdServiceInfo nsdServiceInfo) {
+                // Save the service name.  Android may have changed it in order to
+                // resolve a conflict, so update the name you initially requested
+                // with the name Android actually used.
+                final String serviceName = nsdServiceInfo.getServiceName();
+
+                Log.i(TAG, "Service name: " + serviceName);
+
+                final MonitorActivity ma = monitorActivity;
+                if (ma != null) {
+                    ma.runOnUiThread(() -> {
+                        final TextView statusText = ma.findViewById(R.id.textStatus);
+                        statusText.setText(R.string.waitingForParent);
+
+                        final TextView serviceText = ma.findViewById(R.id.textService);
+                        serviceText.setText(serviceName);
+
+                        final TextView portText = ma.findViewById(R.id.port);
+                        portText.setText(Integer.toString(port));
+                    });
+                }
+
+            }
+
+            @Override
+            public void onRegistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
+                // Registration failed!  Put debugging code here to determine why.
+                Log.e(TAG, "Registration failed: " + errorCode);
+            }
+
+            @Override
+            public void onServiceUnregistered(NsdServiceInfo arg0) {
+                // Service has been unregistered.  This only happens when you call
+                // NsdManager.unregisterService() and pass in this listener.
+
+                Log.i(TAG, "Unregistering service");
+            }
+
+            @Override
+            public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
+                // Unregistration failed.  Put debugging code here to determine why.
+
+                Log.e(TAG, "Unregistration failed: " + errorCode);
+            }
+        };
+
+        nsdManager.registerService(
+                serviceInfo, NsdManager.PROTOCOL_DNS_SD, registrationListener);
+    }
+
+    /**
+     * Unregister the service and assigns the listener
+     * to null.
+     */
+    private void unregisterService() {
+        if (registrationListener != null) {
+            Log.i(TAG, "Unregistering monitoring service");
+
+            nsdManager.unregisterService(registrationListener);
+            registrationListener = null;
+        }
+    }
+
+    private void createNotificationChannel() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            NotificationChannel serviceChannel = new NotificationChannel(
+                    CHANNEL_ID,
+                    "Foreground Service Channel",
+                    NotificationManager.IMPORTANCE_DEFAULT
+            );
+            notificationManager.createNotificationChannel(serviceChannel);
+        }
+    }
+
+    private Notification buildNotification() {
+        CharSequence text = "Child Device";
+        // Set the info for the views that show in the notification panel.
+        NotificationCompat.Builder b = new NotificationCompat.Builder(this, CHANNEL_ID);
+        b.setSmallIcon(R.drawable.listening_notification)  // the status icon
+                .setOngoing(true)
+                .setTicker(text)  // the status text
+                .setContentTitle(text);  // the label of the entry
+        return b.build();
+    }
+
+
+    @Override
+    public void onDestroy() {
+        Thread mt = monitorThread;
+        if (mt != null) {
+            mt.interrupt();
+            monitorThread = null;
+        }
+
+        unregisterService();
+
+        connectionToken = null;
+        if (currentSocket != null) {
+            try {
+                currentSocket.close();
+                currentSocket = null;
+            } catch (IOException e) {
+                Log.e(TAG, "Failed to close active socket on port " + currentPort);
+            }
+        }
+
+        // Cancel the persistent notification.
+        int NOTIFICATION = R.string.listening;
+        notificationManager.cancel(NOTIFICATION);
+
+        stopForeground(true);
+        // Tell the user we stopped.
+        Toast.makeText(this, R.string.stopped, Toast.LENGTH_SHORT).show();
+        super.onDestroy();
+    }
+
+    @Override
+    public IBinder onBind(Intent intent) {
+        return binder;
+    }
+
+    public class MonitorBinder extends Binder {
+        MonitorService getService() {
+            return MonitorService.this;
+        }
+    }
+
+}