Detect when there is an Internet connection available on Android

In this method just current activity receive this event
Add to android Manifest

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

In your activity, create a Broadcast Receiver:

private BroadcastReceiver networkStateReceiver=new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo ni = manager.getActiveNetworkInfo();
        doSomethingOnNetworkChange(ni);
    }
};
@Override
public void onResume() {
    super.onResume();
    registerReceiver(networkStateReceiver, new IntentFilter(android.net.ConnectivityManager.CONNECTIVITY_ACTION));
}

@Override
public void onPause() {
    unregisterReceiver(networkStateReceiver);
    super.onPause();
}

References
https://stackoverflow.com/questions/6169059/android-event-for-internet-connectivity-state-change