What 's Wrong In My RxAndroid Code Text View Not Update

This 's my first RxAndroid. I'm try to solve problem for 3 days. txHello not update on next() method. It update after end loop.

Pleas help.

public class MainActivity extends AppCompatActivity {

    TextView txHello;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn = findViewById(R.id.button);
        txHello = findViewById(R.id.hello);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Observable<String> observer = Observable.just("1", "2", "3", "4", "5", "6", "7", "8", "9", "10");
                observer.observeOn(AndroidSchedulers.mainThread())
                        .subscribeOn(Schedulers.computation())
                        .subscribe(new Observer<String>() {
                            @Override
                            public void onSubscribe(Disposable d) {
                                txHello.setText("------- hello world -------");
                                txHello.append("\nStart From thread " + Thread.currentThread().getName());
                            }

                            @Override
                            public void onNext(String s) {
                                txHello.append("\n"+s +" From thread "+ Thread.currentThread().getName());
                                try {
                                    Thread.sleep(250);
                                } catch (InterruptedException e) {
                                    Log.e("Thread Sleep", e.getMessage());
                                }
                            }

                            @Override
                            public void onError(Throwable e) {

                            }

                            @Override
                            public void onComplete() {

                            }
                        });

            }
        });

    }
}

Thank u very much "KuLdip PaTel"
I can solve my problem with intervalRange Operator.
Problem is Thread.sleep(). Like u comment.

public class MainActivity extends AppCompatActivity {
       TextView txHello;
       @Override
       protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            Button btn = findViewById(R.id.button);
            txHello = findViewById(R.id.hello);

            btn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Observable<Long> obInterval = Observable.intervalRange(0L, 10, 0, 500, TimeUnit.MILLISECONDS);
                    obInterval.subscribeOn(Schedulers.computation())
                      .observeOn(AndroidSchedulers.mainThread())
                      .doOnSubscribe(id -> {
                          txHello.setText("------- hello world -------");
                      })
                      .doOnNext(id -> {
                          txHello.append("\n" + id + " Run From thread " + Thread.currentThread()
                                                                                 .getName());
                      })
                      .doOnComplete(() -> {
                           txHello.append("------- ending process -------");                              
                      })
                      .subscribe();
                }
           });

       }
}