CompletableObserver简单的用法跟踪一个任务的结束，不处理复杂的数据传导，例如：

package zhangphil.app;import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;import java.util.concurrent.Callable;import io.reactivex.Completable;
import io.reactivex.CompletableObserver;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.disposables.Disposable;
import io.reactivex.schedulers.Schedulers;public class MainActivity extends AppCompatActivity {private final String TAG = getClass().getSimpleName();@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);test();}private void test() {Completable.fromCallable(new Callable<Object>() {@Overridepublic Object call() throws Exception {try {Thread.sleep(5000);} catch (InterruptedException e) {e.printStackTrace();}Log.d(TAG, "任务结束！");return null;}}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(getCompletableObserver());}private CompletableObserver getCompletableObserver() {return new CompletableObserver() {@Overridepublic void onSubscribe(Disposable d) {Log.d(TAG, "onSubscribe " + System.currentTimeMillis());}@Overridepublic void onComplete() {Log.d(TAG, "onComplete " + System.currentTimeMillis());}@Overridepublic void onError(Throwable e) {}};}
}

代码运行输出：

05-16 14:01:20.908 12292-12292/zhangphil.app D/MainActivity: onSubscribe 1494914480908
05-16 14:01:20.945 12292-12292/zhangphil.app D/InputTransport: Input channel constructed: fd=73
05-16 14:01:20.945 12292-12292/zhangphil.app D/ViewRootImpl@99677a6[MainActivity]: setView = DecorView@de9b5e7[MainActivity] touchMode=true
05-16 14:01:20.949 12292-12292/zhangphil.app W/Activity: AppLock checkAppLockState locked:false verifying:false pkgName = zhangphil.app isInMultiWindowMode:false
05-16 14:01:20.985 12292-12292/zhangphil.app D/ViewRootImpl@99677a6[MainActivity]: MSG_RESIZED_REPORT: ci=Rect(0, 81 - 0, 0) vi=Rect(0, 81 - 0, 0) or=1
05-16 14:01:20.986 12292-12292/zhangphil.app D/ViewRootImpl@99677a6[MainActivity]: MSG_WINDOW_FOCUS_CHANGED 1
05-16 14:01:20.986 12292-12292/zhangphil.app I/InputMethodManager: [IMM] startInputInner - mService.startInputOrWindowGainedFocus
05-16 14:01:20.988 12292-12292/zhangphil.app D/InputTransport: Input channel constructed: fd=74
05-16 14:01:25.911 12292-23777/zhangphil.app D/MainActivity: 任务结束！
05-16 14:01:25.912 12292-12292/zhangphil.app D/MainActivity: onComplete 1494914485912