How to check the internet connection continuously while app is running

Question

I have created code which checks the internet connection at the start but I want it to keep checking for internet connection in the background and notify the user when connection is lost. I'm new to android so can you please write proper code and help me. This code works fine, I just want it so that it runs in the background to keep a check on internet.

public class isNetworkAvailable extends Activity  {
    @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_is_network);
       ;
            if(!isNetworkAvailable()){
                //Create an alert dialog
                AlertDialog.Builder Checkbuilder = new  AlertDialog.Builder(isNetworkAvailable.this);
                Checkbuilder.setIcon(R.drawable.error);
                Checkbuilder.setTitle("Error!");
                Checkbuilder.setMessage("Check Your Internet Connection.");
                //Builder Retry Button

                Checkbuilder.setPositiveButton("Retry", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int id) {
                        //Restart The Activity
                        Intent intent = getIntent();
                        finish();
                        startActivity(intent);

                    }
                });

                Checkbuilder.setNegativeButton("Exit", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        finish();
                    }
                }) ;

                AlertDialog alert=Checkbuilder.create();
                alert.show();

            }



            else {
                if (isNetworkAvailable()){

                    Thread tr=new Thread(){
                        public  void  run(){
                            try {
                                sleep(4);
                            }
                            catch (Exception e){
                                e.printStackTrace();
                            }
                            finally {
                                Intent i = new Intent(isNetworkAvailable.this,MainActivity.class);
                                startActivity(i);

                                finish();
                            }}};tr.start();}}}private boolean isNetworkAvailable(){
            ConnectivityManager connectivityManager=(ConnectivityManager)this.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo activeNetworkInfo=connectivityManager.getActiveNetworkInfo();
            return activeNetworkInfo !=null;

        }
    }

Answer 1

Use ReactiveNetwork lib

ReactiveNetwork is an Android library listening network connection state and Internet connectivity. Library supports both new and legacy network monitoring strategies. Min SDK version = 9

Usage

add this to gradle

dependencies {
  implementation 'com.github.pwittchen:reactivenetwork-rx2:3.0.2'
}

and in your activity

ReactiveNetwork.observeInternetConnectivity()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(isConnectedToInternet -> {
                    // do something with isConnectedToInternet value

                    changeOnlineStatus(isConnectedToInternet ? ConnectionQuality.EXCELLENT : ConnectionQuality.POOR);
                });

it Observe Internet connectivity continuously

for more info link