Question

I need to know how I can detect a switch in Wi-Fi networks, albeit automatically or manually, it doesn’t matter. Is there some kind of intent being broadcasted throughout the system when a switch is detected? Or do I have to manually check if a new network is selected by calling a method on a ConnectivityManager?

Answer 1

At this point in time, I have fixed this like this (haven’t fully tested it yet as I don’t have a second network available at the moment):

I extended the BroadcastReceiver class

private class NetworkSwitcher extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (!action.equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
            return;
        }
        NetworkInfo networkInfo =
            (NetworkInfo)intent.getParcelableExtra(ConnectivityManager.EXTRA_NETWORK_INFO);
        if (networkInfo.isConnected()) {
            if (networkInfo.getType() == ConnectivityManager.TYPE_WIFI) {
                Log.d(TAG, "Network type: " + networkInfo.getTypeName() +
                        " Network subtype: " + networkInfo.getSubtypeName());
                getOwnIpAddress();
                mClient.updateUnicastSocket(mOwnAddress, mUnicastPort);
            }
        } 
        else {
            Log.e(TAG, "Network connection lost");
        }
    }
}

I register this class as a receiver with a filter set to the ConnectivityManager.CONNECTIVITY_ACTION intent (setting it in onResume() and releasing it in onPause()). This ought to catch any automatic Wi-Fi network switch. The getOwnIpAddress retrieves the device’s IP address from the WifiManager.

I’ve also found that it works when I return to the activity from another activity.