Вы можете использовать BroadcastReceiver
public class ConnectivityReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager conMan = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = conMan.getActiveNetworkInfo();
if(intent.getAction().equals(WifiManager.NETWORK_STATE_CHANGED_ACTION)) {
if(netInfo.isConnected()) {
WifiManager wifiManager = (WifiManager) context.getAplicationContext().getSystemService (Context.WIFI_SERVICE);
WifiInfo info = wifiManager.getConnectionInfo ();
String ssid = info.getSSID();
Log.d("Wifi Connected", "Wifi name is "+ info.getSSID());
}
}
}
}