Android - Auto detect network connection change event - Java

Step 1: Create a Receiver

- Create class NetworkChangeReceiver:

public class NetworkChangeReceiver extends BroadcastReceiver {
private NetworkListener networkListener;

public void setNetworkListener(NetworkListener networkListener) {
this.networkListener = networkListener;
}

public NetworkChangeReceiver() {

}

@Override
public void onReceive(Context context, Intent intent) {
if(networkListener!=null)
networkListener.onConnectionChange();
}

public interface NetworkListener {
void onConnectionChange();
}
}

- In AndroidManifest.xml add in tag application:

<receiver
android:name=".yourPath.NetworkChangeReceiver"
android:label="NetworkChangeReceiver" >
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
</intent-filter>
</receiver>

- Add permission in AndroidManifest.xml:

<uses-permission android:name="android.permission.INTERNET" />

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Step 2: Implement in Activity:

- Create field: 

private NetworkChangeReceiver networkChangeReceiver;

- Implements NetworkChangeReceiver.NetworkListener

- Ctrl + I:

@Override
public void onConnectionChange() {
// do something here...
}

- OnStart() of Activity:

if (networkChangeReceiver == null) 

networkChangeReceiver = new NetworkChangeReceiver();
networkChangeReceiver.setNetworkListener(this);

registerReceiver(networkChangeReceiver,
new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));

- OnStop() in Activity:

if (networkChangeReceiver != null) {
networkChangeReceiver.setNetworkListener(null);
unregisterReceiver(networkChangeReceiver);
}