android - 我如何让 RxJava2 Completable andThen() 工作？

Question

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

阅读RxJava Completable的文档后我希望 public final Single andThen(SingleSource next)为我完成工作。但以下代码 fragment 仅记录“Completable”。不记录“单个”和“来自单个”。

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

Completable 永远不会完成。您需要在发射器上调用 .onComplete()。

因此您的可完成内容将如下所示:

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