RxJava/RxAndroid : doOnNext

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import io.reactivex.Observable;
import io.reactivex.Observer;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Consumer;
import io.reactivex.schedulers.Schedulers;

public class MainActivity extends AppCompatActivity {
    private String TAG = "输出";

    private Observer<Integer> mObserver = new Observer<Integer>() {
        @Override
        public void onSubscribe(Disposable d) {

        }

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

        @Override
        public void onComplete() {
            Log.d(TAG, "onComplete");
        }

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

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Integer[] numbers = new Integer[]{0, 1, 2, 3, 4};

        Observable.fromArray(numbers)
                .takeLast(3)
                .doOnNext(new Consumer<Integer>() {
                    @Override
                    public void accept(Integer integer) throws Exception {
                        Log.d(TAG, "accept:" + integer);
                    }
                })
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeWith(mObserver);
    }
}

output:

01-19 15:01:48.904 11409-11429/zhangphil.book D/输出: accept:2
01-19 15:01:48.906 11409-11429/zhangphil.book D/输出: accept:3
01-19 15:01:48.906 11409-11429/zhangphil.book D/输出: accept:4
01-19 15:01:48.983 11409-11409/zhangphil.book D/输出: onNext:2
01-19 15:01:48.983 11409-11409/zhangphil.book D/输出: onNext:3
01-19 15:01:48.983 11409-11409/zhangphil.book D/输出: onNext:4
01-19 15:01:48.983 11409-11409/zhangphil.book D/输出: onComplete