RxAndroid2/RxJava2的merge操作合并若干个Observable为单个可观测的Observable，形成单一线性的Observable输出结果，例如代码：

package zhangphil.app;import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;import java.util.concurrent.Callable;import io.reactivex.Observable;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.CompositeDisposable;
import io.reactivex.functions.BiFunction;
import io.reactivex.observers.DisposableObserver;
import io.reactivex.schedulers.Schedulers;public class MainActivity extends AppCompatActivity {private final String TAG = getClass().getSimpleName();private CompositeDisposable mCompositeDisposable = new CompositeDisposable();@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);test();}private void test() {DisposableObserver disposableObserver = new DisposableObserver<String>() {@Overridepublic void onNext(String s) {Log.d(TAG, "#####开始#####");Log.d(TAG + "数据", String.valueOf(s));Log.d(TAG, "#####结束#####");}@Overridepublic void onComplete() {}@Overridepublic void onError(Throwable e) {Log.e(TAG, e.toString(), e);}};mCompositeDisposable.add(Observable.merge(getObservableA(null),getObservableB(null),getObservableA(null),getObservableB(null)).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribeWith(disposableObserver));}@Overrideprotected void onDestroy() {super.onDestroy();// 如果退出程序，就清除后台任务mCompositeDisposable.clear();}private Observable<String> getObservableA(Object o) {return Observable.fromCallable(new Callable<String>() {@Overridepublic String call() throws Exception {try {Thread.sleep(500); // 假设此处是耗时操作} catch (Exception e) {e.printStackTrace();}return "A";}});}private Observable<String> getObservableB(Object o) {return Observable.fromCallable(new Callable<String>() {@Overridepublic String call() throws Exception {try {Thread.sleep(1000); // 假设此处是耗时操作} catch (Exception e) {e.printStackTrace();}return "B";}});}
}

代码输出结果：

05-15 13:40:41.929 12972-12972/zhangphil.app D/MainActivity: #####开始#####
05-15 13:40:41.929 12972-12972/zhangphil.app D/MainActivity数据: A
05-15 13:40:41.929 12972-12972/zhangphil.app D/MainActivity: #####结束#####
05-15 13:40:42.930 12972-12972/zhangphil.app D/MainActivity: #####开始#####
05-15 13:40:42.930 12972-12972/zhangphil.app D/MainActivity数据: B
05-15 13:40:42.930 12972-12972/zhangphil.app D/MainActivity: #####结束#####
05-15 13:40:43.430 12972-12972/zhangphil.app D/MainActivity: #####开始#####
05-15 13:40:43.431 12972-12972/zhangphil.app D/MainActivity数据: A
05-15 13:40:43.431 12972-12972/zhangphil.app D/MainActivity: #####结束#####
05-15 13:40:44.431 12972-12972/zhangphil.app D/MainActivity: #####开始#####
05-15 13:40:44.431 12972-12972/zhangphil.app D/MainActivity数据: B
05-15 13:40:44.431 12972-12972/zhangphil.app D/MainActivity: #####结束#####