如何让RxJava2 Completable和Thhen()工作？

Question

在我的Android应用程序中,我想更新数据库条目的一部分(使用Room),然后在更新完成后立即从数据库中读取整个条目.

在阅读了RxJava Completable的文档后,我希望公开的最终Single andThen(SingleSource next)为我完成这项工作.但以下代码段仅记录"可完成".不记录"Single"和"From Single".

import io.reactivex.Completable;
import io.reactivex.CompletableEmitter;
import io.reactivex.CompletableOnSubscribe;
import io.reactivex.Single;
import io.reactivex.functions.Consumer;

Completable completable = Completable.create(new CompletableOnSubscribe() {
    @Override
    public void subscribe(CompletableEmitter e) throws Exception {
        Log.e(LOG, "Completable");
    }
});

Single<Long> single = Single.fromCallable(new Callable<Long>() {
    @Override
    public Long call() throws Exception {
        Log.e(LOG, "Single");
        return Long.valueOf(123);
    }
});

completable.andThen(single).subscribe(new Consumer<Long>() {
    @Override
    public void accept(@NonNull Long aLong) throws Exception {
        Log.e(LOG, "From Single: " + aLong.toString());
    }
}, new Consumer<Throwable>() {
    @Override
    public void accept(@NonNull Throwable throwable) throws Exception {
        Log.e(LOG, "Error from Single");
    }
});

Answer 1

将Completable永远不会完成.你需要调用.onComplete()发射器.

所以你的完成将看起来像:

Completable completable = Completable.create(new CompletableOnSubscribe() {
    @Override
    public void subscribe(CompletableEmitter e) throws Exception {
        Log.e(LOG, "Completable");
        e.onComplete();
    }
});