MainActivity.java

package nisrulz.github.sample.usingrxjava2;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;
import java.util.concurrent.TimeUnit;

public class MainActivity extends AppCompatActivity {

  private static final String TAG = "MainActivity";

  Observable<?> observable;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Basic Example
    basicRxJava2Example();

    // Creating Observable using just
    Log.i(TAG, "Creating Observable using just");
    observable = Observable.just("Hello World");
    commonRxJava2Example(observable);

    // Creating Observable using range
    Log.i(TAG, "Creating Observable using range");
    observable = Observable.range(0, 5);
    commonRxJava2Example(observable);

    // Creating Observable using from
    Log.i(TAG, "Creating Observable using fromArray");
    observable = Observable.fromArray(new String[] { "H", "e", "l", "l", "o" });
    commonRxJava2Example(observable);

    // Creating Observable using interval
    Log.i(TAG, "Creating Observable using interval");
    observable = Observable.interval(2, TimeUnit.SECONDS);
    commonRxJava2Example(observable);
  }

  void commonRxJava2Example(Observable<?> observable) {

    // 2. Create an Observer
    Observer<Object> observer = new Observer<Object>() {
      @Override
      public void onSubscribe(Disposable d) {
        Log.i(TAG, "onSubscribe: ");
      }

      @Override
      public void onNext(Object value) {
        Log.i(TAG, "onNext: " + value);
      }

      @Override
      public void onError(Throwable e) {
        Log.i(TAG, "onError: ");
      }

      @Override
      public void onComplete() {
        Log.i(TAG, "onComplete: All Done!");
      }
    };

    //3. Create our subscription i.e Subscribe Observable to Observer
    observable.subscribe(observer);
  }

  void basicRxJava2Example() {
    // 1. Create an Observable
    Observable<Integer> observable = Observable.create(new ObservableOnSubscribe<Integer>() {
      @Override
      public void subscribe(ObservableEmitter<Integer> e) throws Exception {
        //Use onNext to emit each item in the stream//
        e.onNext(1);
        e.onNext(2);
        e.onNext(3);
        e.onNext(4);

        //Once the Observable has emitted all items in the sequence, call onComplete//
        e.onComplete();
      }
    });

    // 2. Create an Observer
    Observer<Integer> observer = new Observer<Integer>() {
      @Override
      public void onSubscribe(Disposable d) {
        Log.i(TAG, "onSubscribe: ");
      }

      @Override
      public void onNext(Integer value) {
        Log.i(TAG, "onNext: " + value);
      }

      @Override
      public void onError(Throwable e) {
        Log.i(TAG, "onError: ");
      }

      @Override
      public void onComplete() {
        Log.i(TAG, "onComplete: All Done!");
      }
    };

    //3. Create our subscription i.e Subscribe Observable to Observer
    observable.subscribe(observer);
  }
}