Implement connectivity listener

app/src/main/AndroidManifest.xml

@@ -5,10 +5,11 @@
     <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
     <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.READ_PHONE_STATE" />
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
-    
+
     <application android:label="@string/app_name" android:icon="@drawable/ic_launcher" android:allowBackup="true" android:theme="@style/TraccarTheme">
         
         <activity android:name=".MainActivity">

app/src/main/java/org/traccar/client/NetworkManager.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2015 Anton Tananaev (anton.tananaev@gmail.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.traccar.client;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.net.ConnectivityManager;
+import android.net.NetworkInfo;
+
+public class NetworkManager extends BroadcastReceiver {
+
+    private Context context;
+    private NetworkHandler handler;
+
+    public NetworkManager(Context context, NetworkHandler handler) {
+        this.context = context;
+        this.handler = handler;
+    }
+
+    public interface NetworkHandler {
+        void onNetworkUpdate(boolean isOnline);
+    }
+
+    public boolean isOnline() {
+        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
+        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
+        return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
+    }
+
+    public void start() {
+        IntentFilter filter = new IntentFilter();
+        filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
+        context.registerReceiver(this, filter);
+    }
+
+    public void stop() {
+        context.unregisterReceiver(this);
+    }
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION) && handler != null) {
+            handler.onNetworkUpdate(intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, false));
+        }
+    }
+
+}

app/src/main/java/org/traccar/client/TrackingController.java

@@ -20,10 +20,11 @@ import android.content.SharedPreferences;
 import android.os.Handler;
 import android.preference.PreferenceManager;
 
-public class TrackingController implements PositionProvider.PositionListener {
+public class TrackingController implements PositionProvider.PositionListener, NetworkManager.NetworkHandler {
 
     private static final int RETRY_DELAY = 30 * 1000;
 
+    private boolean isOnline;
     private boolean isWaiting;
 
     private Context context;
@@ -32,6 +33,7 @@ public class TrackingController implements PositionProvider.PositionListener {
 
     private PositionProvider positionProvider;
     private DatabaseHelper databaseHelper;
+    private NetworkManager networkManager;
 
     public TrackingController(Context context) {
         this.context = context;
@@ -42,13 +44,18 @@ public class TrackingController implements PositionProvider.PositionListener {
                 preferences.getString(MainActivity.KEY_PROVIDER, null),
                 Integer.parseInt(preferences.getString(MainActivity.KEY_INTERVAL, null)) * 1000);
         databaseHelper = new DatabaseHelper(context);
+        networkManager = new NetworkManager(context, this);
+        isOnline = networkManager.isOnline();
     }
 
     public void start() {
+        read();
         positionProvider.startUpdates();
+        networkManager.start();
     }
 
     public void stop() {
+        networkManager.stop();
         positionProvider.stopUpdates();
         handler.removeCallbacksAndMessages(null);
     }
@@ -61,12 +68,38 @@ public class TrackingController implements PositionProvider.PositionListener {
         }
     }
 
+    @Override
+    public void onNetworkUpdate(boolean isOnline) {
+        if (!this.isOnline && isOnline) {
+            read();
+        }
+        this.isOnline = isOnline;
+    }
+
+    //
+    // State transition examples:
     //
     // write -> read -> send -> delete -> read
     //
     // read -> send -> retry -> read -> send
     //
 
+    private void write(Position position) {
+        databaseHelper.insertPositionAsync(position, new DatabaseHelper.DatabaseHandler<Void>() {
+            @Override
+            public void onSuccess(Void result) {
+                if (isOnline && isWaiting) {
+                    read();
+                    isWaiting = false;
+                }
+            }
+
+            @Override
+            public void onFailure(RuntimeException error) {
+            }
+        });
+    }
+
     private void read() {
         databaseHelper.selectPositionAsync(new DatabaseHelper.DatabaseHandler<Position>() {
             @Override
@@ -85,22 +118,6 @@ public class TrackingController implements PositionProvider.PositionListener {
         });
     }
 
-    private void write(Position position) {
-        databaseHelper.insertPositionAsync(position, new DatabaseHelper.DatabaseHandler<Void>() {
-            @Override
-            public void onSuccess(Void result) {
-                if (isWaiting) {
-                    read();
-                    isWaiting = false;
-                }
-            }
-
-            @Override
-            public void onFailure(RuntimeException error) {
-            }
-        });
-    }
-
     private void delete(Position position) {
         databaseHelper.deletePositionAsync(position.getId(), new DatabaseHelper.DatabaseHandler<Void>() {
             @Override