java - RxJava2 : need help to fix an issue in code

Question

我是 RxJava 编程新手，需要帮助来处理我的代码问题。我有以下代码:

public Single<List<Modifications>> loadModificationsImages() {
    return Observable.fromCallable(DataStoreRepository::loadModifications)
            .subscribeOn(Schedulers.io())
            .flatMapIterable(list -> list)
            .doOnNext(item -> {
                Observable.fromIterable(item.images)
                        .forEach(image -> {
                            ApiRepository.getModificationsImages(item.id, image.id)
                                    .subscribeOn(Schedulers.computation())
                                    .retry(3)
                                    .subscribe(response -> {
                                        InputStream is = response.byteStream();

                                        BitmapFactory.Options options = new BitmapFactory.Options();
                                        options.inPreferredConfig = Bitmap.Config.RGB_565;

                                        Bitmap bitmap = BitmapFactory.decodeStream(is, null, options);

                                        String contentSubType = response.contentType().subtype();
                                        String fileName = "modifications_id_" + item.id + "_image_id_" + image.id + "." + contentSubType;
                                        FileUtil.saveBitmap(bitmap, fileName);

                                        Modifications.Images img = new Modifications.Images(image.id, fileName, image.type);
                                        DataStoreRepository.updateModificationsImage(img, item.id);
                                    });
                        });
            })
            .toList();
} 

它工作得很好，但我需要收集每个 Modifications.Images放入集合中并将其传递给方法 ( DataStoreRepository.updateListOfModificationsImage(List<Modifications.Images> images, int id) ) 以更新数据库。所以，这一行的问题是:

Modifications.Images img = new Modifications.Images(image.id, fileName, image.type);
DataStoreRepository.updateModificationsImage(img, item.id);

它只是用单个项目覆盖数据库中的记录。我尝试通过应用 Collection 来修改给定的代码，但它对我不起作用。

感谢您的帮助!

Answer 1

在回调内订阅几乎总是错误的。否则，您应该toList图像，然后调用批量更新方法:

public Single<List<Modifications>> loadModificationsImages() {
    return Observable.fromCallable(DataStoreRepository::loadModifications)
            .subscribeOn(Schedulers.io())
            .flatMapIterable(list -> list)
            .flatMapSingle(item -> 
                Observable.fromIterable(item.images)
                .flatMap(image ->
                    ApiRepository.getModificationsImages(item.id, image.id)
                    .subscribeOn(Schedulers.io())
                    .retry(3)
                    .map(response -> {
                        InputStream is = response.byteStream();

                        BitmapFactory.Options options = new BitmapFactory.Options();
                        options.inPreferredConfig = Bitmap.Config.RGB_565;

                        Bitmap bitmap = BitmapFactory.decodeStream(is, null, options);

                        String contentSubType = response.contentType().subtype();
                        String fileName = "modifications_id_" + item.id + "_image_id_"
                            + image.id + "." + contentSubType;
                        FileUtil.saveBitmap(bitmap, fileName);

                        Modifications.Images img = new Modifications.Images(
                            image.id, fileName, image.type);
                        return img;
                    })
                )
                .toList()
                .doOnSuccess(images -> 
                    DataStoreRepository.updateListOfModificationsImage(images, image.id)
                )
            );
}