修复编译报错

app/src/main/java/com/xypower/mpapp/NetworkChangedReceiver.java

@@ -16,10 +16,14 @@ public class NetworkChangedReceiver extends BroadcastReceiver {
 
     private WeakReference<MicroPhotoService> mService;
 
+    public NetworkChangedReceiver() {
+        super();
+
+        mService = null;
+    }
     public NetworkChangedReceiver(MicroPhotoService service) {
         mService = new WeakReference<>(service);
     }
-
     private String getConnectionType(int type) {
         String connType = "";
         if (type == ConnectivityManager.TYPE_MOBILE) {