Check Internet Connection in Android (API Level 29) Using Network Callback

CheckNetwork.java

/*
You need to call the below method once. It register the callback and fire it when there is a change in network state.
Here I used a Global Static Variable, So I can use it to access the network state in anyware of the application.
*/

// You need to pass the context when creating the class
public CheckNetwork(Context context) {
    this.context = context;
}

// Network Check
public void registerNetworkCallback()
{
    try {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkRequest.Builder builder = new NetworkRequest.Builder();

        connectivityManager.registerDefaultNetworkCallback(new ConnectivityManager.NetworkCallback(){
                    @Override
                    public void onAvailable(Network network) {
                        Variables.isNetworkConnected = true; // Global Static Variable
                    }
                    @Override
                    public void onLost(Network network) {
                        Variables.isNetworkConnected = false; // Global Static Variable
                    }
                }

        );
        Variables.isNetworkConnected = false;
    }catch (Exception e){
        Variables.isNetworkConnected = false;
    }
}

GlobalVariables.java

public class Variables {
    // Global variable used to store network state
    public static boolean isNetworkConnected = false;
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // Register Callback - Call this in your app start!
        CheckNetwork network = new CheckNetwork(getApplicationContext());
        network.registerNetworkCallback();
        
        // Check network connection
        if (Variables.isNetworkConnected){
            // Internet Connected
        }else{
            // Not Connected   
        }
    }
}

@baha2046a

Register the callback on onCreate may cause it add more then one times.

Tha'ts not whats happening in actual, Registration is done only done once, than a global static is set. As for the update of value, It is done by android system once registered ( something similar to pub-sub way, can't explain fully here ). So there is essentially no overhead. If you accidentally try to register it again, no effect takes place.
On other hand, the old way to initiate NetworkInfo, and then find out if network is available, That was something that was being done everytime check was asked for. Since Android 10, Google is Promoting pub-sub/callback/relay style of apis instead of old functional apis because of performance reason. Anything that needs to be queried from system should be subscribed for, thats the direction they seems to going for.

Hi
My own version for checking if the user already doesn't have a connection, also handle the connection change status
https://gist.github.com/ayoubrem/81689ca066f77ecd1ebb5e14de245e6d

hi bro, your link is page not found, Do you share again? Thank you

@SuppressLint("NewApi")
@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
private void doWork() {

   ConnectivityManager cm=(ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);


    cm.registerDefaultNetworkCallback(new ConnectivityManager.NetworkCallback(){

        public void onAvailable(Network network) {
            Log.e("hola", "The default network is now: " + network);
             network=cm.getActiveNetwork();
              if(network!=null){
                  SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
                  String minMagnitude = sharedPrefs.getString(
                          getString(R.string.settings_min_magnitude_key),
                          getString(R.string.settings_min_magnitude_default));
                  String orderBy = sharedPrefs.getString(
                          getString(R.string.settings_order_by_key),
                          getString(R.string.settings_order_by_default)
                                                  );

                  if (orderBy.equals(getString(R.string.settings_order_by_default))){
                      extractdata(minMagnitude, "magnitude-asc");
                  }else{
                      extractdata(minMagnitude,orderBy);

                  }

              }
        }

        public void onCapabilitiesChanged(@NonNull Network network, @NonNull NetworkCapabilities networkCapabilities) {
            super.onCapabilitiesChanged(network, networkCapabilities);
            Log.i(TAG,network+" "+networkCapabilities.toString()+" "+networkCapabilities.hasCapability(NET_CAPABILITY_INTERNET));
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    View loadingIndicator = findViewById(R.id.progressBar);
                    loadingIndicator.setVisibility(View.VISIBLE);
                    rvCourses=findViewById(R.id.rvCourses);
                    mEmptyTextview=findViewById(R.id.empty_view);
                    mEmptyTextview.setVisibility(View.GONE);
                    rvCourses.setVisibility(View.VISIBLE);
                }
            });
            if(networkCapabilities.hasCapability(NET_CAPABILITY_INTERNET)){

                SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(MainActivity.this);
                String minMagnitude = sharedPrefs.getString(
                        getString(R.string.settings_min_magnitude_key),
                        getString(R.string.settings_min_magnitude_default));
                String orderBy = sharedPrefs.getString(
                        getString(R.string.settings_order_by_key),
                        getString(R.string.settings_order_by_default)
                );

                if (orderBy.equals(getString(R.string.settings_order_by_default))){
                    extractdata(minMagnitude, "magnitude-asc");
                }else{
                    extractdata(minMagnitude,orderBy);

                }


            }
        }

           public void onLost(Network network) {
            /*View loadingIndicator = findViewById(R.id.progressBar);
            loadingIndicator.setVisibility(View.GONE);
            Log.e(TAG, "The application no longer has a default network. The last default network was " + network);
            rvCourses=findViewById(R.id.rvCourses);
            mEmptyTextview=findViewById(R.id.empty_view);
            mEmptyTextview.setText("NO INTERNET CONNECTION");
            rvCourses.setVisibility(View.GONE);
            mEmptyTextview.setVisibility(View.VISIBLE);*/

            runOnUiThread(new Runnable() {
                @Override
                public void run() {

                    View loadingIndicator = findViewById(R.id.progressBar);
                    loadingIndicator.setVisibility(View.GONE);
                    Log.e(TAG, "The application no longer has a default network. The last default network was " + network);
                    rvCourses=findViewById(R.id.rvCourses);
                    mEmptyTextview=findViewById(R.id.empty_view);
                    mEmptyTextview.setText("NO INTERNET CONNECTION");
                    rvCourses.setVisibility(View.GONE);
                    mEmptyTextview.setVisibility(View.VISIBLE);

                }
            });


        }





    }

    );


}

Hope this helps ;P

@PasanBhanu
please explain why you are using

        NetworkRequest.Builder builder = new NetworkRequest.Builder();

@PasanBhanu please explain why you are using

        NetworkRequest.Builder builder = new NetworkRequest.Builder();

Reminiscent of older code, Before we found about registerDefault from google team, older version of code was basically build a network request object, add the wifi module and/or bluetooth module (basically any and all network interface you want to observe) and then use that object to registerNetworkCallback

When you use registerDefaultNetworkCallback, it basically connects to the lower level network pool with default options, so you don't need to (but you still can if you want) build your own network object.