How can I receive a notification when the device loses network connectivity in android L (API 21)

Question

I\'m using this code to be notified when the connection is lost in API 20 and down.

registerReceiver(getConnectivityStateBroadcastReceiver(), new IntentFilte         


        

Answer 1

Try this if you need

• register to the network state changes
• consider all network interfaces
• want to be notified if network is available for any interface
• that code supports API>20 (you can add also legacy API support easily)

Declare the necessary variables in your class:

private static final HashMap mNetworkStates = new HashMap<>();
private final Object mSyncNetworkState = new Object();
private Boolean mNetworkState;

Define your method which monitors the interface changes. mNetworkState shows always if at least one network interface is connected.

private void registerNetworkStateInfo(@NonNull final Context context) throws Exception {
    final ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkRequest.Builder builder = new NetworkRequest.Builder();

    if (connectivityManager != null) {
        connectivityManager.registerNetworkCallback(
                builder.build(),
                new ConnectivityManager.NetworkCallback() {
                    @Override
                    public void onAvailable(@NonNull Network network) {
                        mNetworkStates.put(network, true);
                        synchronized (mSyncNetworkState){
                            mNetworkState = true;
                        }

                        Log.d("Network state", "Network state: true");
                    }

                    @Override
                    public void onLost(@NonNull Network network) {
                        mNetworkStates.put(network, false);
                        synchronized (mSyncNetworkState){
                            mNetworkState = false;
                            Log.d("Network state", "Network state: false");

                            mNetworkStates.forEach(new BiConsumer() {
                                @Override
                                public void accept(Network nextNetwork, Boolean state) {
                                    if (state.equals(true)) {
                                        mNetworkState= true;
                                        Log.d("Network state", "Network state: but true");
                                    }
                                }
                            });
                        }
                    }
                }
        );
    } else {
        synchronized (mSyncNetworkState){
            mNetworkState = false;
        }
        throw new Exception("Connectivity Manager is not available");
    }
}

Use your mNetworkState

synchronized (mSyncNetworkState){
    if (!mNetworkState) {
        throw new Exception("No network available");
    }
}