Rxjava2 just method - 如何运行在另一个线程上插入房间？

Question

我有一个房间持久数据库插入方法，如下所示：

@Dao
public interface CountriesDao{

    @Insert(onConflict = REPLACE)
    List<Long> addCountries(List<CountryModel> countryModel);
}

我意识到这不能在主线程上运行。这是我定义数据库的方式：

Room.inMemoryDatabaseBuilder(context.getApplicationContext(), MyDatabase.class).build();

我正在尝试使用 rxjava2，这样我就不会运行在主线程上。我创建了以下方法：

public void storeCountries(List<CountryModel> countriesList) {
        Observable.just(db.countriesDao().addCountries(countriesList))
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new DefaultSubscriber<List<Long>>(){
            @Override
            public void onSubscribe(@NonNull Disposable d) {
                super.onSubscribe(d);
            }

            @Override
            public void onNext(@NonNull List<Long> longs) {
                super.onNext(longs);
                Timber.d("insert countries transaction complete");
            }

            @Override
            public void onError(@NonNull Throwable e) {
                super.onError(e);
                Timber.d("error storing countries in db"+e);
            }

            @Override
            public void onComplete() {
                Timber.d("insert countries transaction complete");
            }
        });
    }

对我来说，现在显然运行正在另一个线程上。不是主线程，但是当我运行这段代码时，我得到以下错误：

完整的堆栈跟踪如下。为什么会这样？

Process: com.mobile.myapp.staging, PID: 12990
java.lang.IllegalStateException: Fatal Exception thrown on Scheduler. Caused by: java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time. at io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:111) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6077) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756) Caused by: java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time. at android.arch.persistence.room.RoomDatabase.assertNotMainThread(RoomDatabase.java:138) at android.arch.persistence.room.RoomDatabase.beginTransaction(RoomDatabase.java:185) at com.mobile.myapp.data.room.dao.CountriesDao_Impl.addCountries(CountriesDao_Impl.java:165) at com.mobile.myapp.data.repositories.CountryRepository.storeCountries(CountryRepository.java:42) at com.mobile.myapp.UI.mvp.Presenters.SignUpPresenter.cacheCountries(SignUpPresenter.java:40) at com.mobile.myapp.UI.mvp.Presenters.SignUpPresenter$CountriesSubscriber.onNext(SignUpPresenter.java:60) at com.mobile.myapp.UI.mvp.Presenters.SignUpPresenter$CountriesSubscriber.onNext(SignUpPresenter.java:49) at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.drainNormal(ObservableObserveOn.java:200) at io.reactivex.internal.operators.observable.ObservableObserveOn$ObserveOnObserver.run(ObservableObserveOn.java:252) at io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run(HandlerScheduler.java:109) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6077) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

不重要，但如果你需要知道 defaultSubscriber class 是什么样子，它是：

DefaultSubscriber.java

public class DefaultSubscriber<T> implements Observer<T> {

Disposable disposable;

@Override
public void onSubscribe(@NonNull Disposable d) {
    disposable = d;
}

@Override
public void onNext(@NonNull T t) {

}

@Override
public void onError(@NonNull Throwable e) {
    Timber.e(e);
}

@Override
public void onComplete() {

}

public void unsubscribe(){
    if(disposable!=null && !disposable.isDisposed()){
        disposable.dispose();
    }
  }
}

Answer 1

这是一个常见的错误：just() 不会在括号内执行 "code"，因为 just 取值，而不是计算。你需要 fromCallable:

Observable.fromCallable(() -> db.countriesDao().addCountries(countriesList))

Answer 2

你也可以使用 Single observable

        Single.create(new SingleOnSubscribe<List<Long>>() {
        @Override
        public void subscribe(SingleEmitter<List<Long>> emitter) throws Exception {
            try {
                List<Long> ids = db.countriesDao().addCountries(countriesList);
                emitter.onSuccess(ids);
            } catch (Throwable t) {
                emitter.onError(t);
            }
        }})
    .observeOn(AndroidSchedulers.mainThread())
    .subscribeOn(Schedulers.io())
    .subscribeWith(new DisposableSingleObserver<Long>() {
        @Override
        public void onSuccess(List<Long> ids) {

        }

        @Override
        public void onError(Throwable e) {

        }
});

Answer 3

更好的是，您可以使用 Completable。其描述：表示一个没有任何值的计算，但仅指示完成或异常。

Completable.fromAction(() -> db.countriesDao().addCountries(list)).subscribe();

Answer 4

Note: Room doesn't support database access on the main thread unless you've called allowMainThreadQueries() on the builder because it might lock the UI for a long period of time. Asynchronous queries - queries that return instances of LiveData or Flowable are exempt from this rule because they asynchronously run the query on a background thread when needed.

所以你的代码可以是这样的

Completable.fromAction(() -> db.countriesDao()
                .addCountries(list))
                .subscribeOn(Schedulers.io())
                .subscribe();

Answer 5

从room room 2.1.0-alpha02,插入时可以使用(Completeable,Single,Maybe)( https://medium.com/androiddevelopers/room-rxjava-acb0cd4f3757)

例子

@Dao
interface UserDao{
     @Insert
     Completable insert(final User user); // currently, we must put final before user variable or you will get error when compile
}

正在使用

db.userDao().insert(user).subscribeOn(Schedulers.io()).subscribe(new Action() {
    @Override
    public void run() throws Exception {
        // success
    }
}, new Consumer < Throwable > () {
    @Override
    public void accept(Throwable throwable) throws Exception {
        // error
    }
});

Answer 6

确保你已经添加了两个依赖项， “实施 'io.reactivex.rxjava3:rxjava:3.0.0' 实施 'io.reactivex.rxjava3:rxandroid:3.0.0'"

Rxjava2 just method - 如何运行在另一个线程上插入房间？

Rxjava2 just method - how to run room insertion on another thread?

android

rx-java

android-room

Rxjava2 just method - 如何 运行 在另一个线程上插入房间？

Rxjava2 just method - how to run room insertion on another thread?

android

rx-java

android-room

Rxjava2 just method - 如何运行在另一个线程上插入房间？