如何在android room和rxjava 2中插入数据并获取id作为out参数? [英] How to insert data and get id as out parameter in android room and rxjava 2?

问题描述

插入查询

@Insert(onConflict = OnConflictStrategy.REPLACE)
long insertProduct(Product product);   //product id is auto generated 

视图模型

public Completable insertProduct(final String productName) {
    return new CompletableFromAction(() -> {
        Product newProduct = new Product();
        newProduct.setProductName(productName);
        mProductDataSource.insertOrUpdateProduct(newProduct);
    });
}

在我调用上述函数的活动中，我使用了CompositeDisposable.

In activity where I called this above function I used CompositeDisposable.

CompositeDisposable mDisposable = new CompositeDisposable();

 mDisposable.add(mViewModel.insertProduct(productName))
      .subscribeOn(Schedulers.io())
      .observeOn(AndroidSchedulers.mainThread())
      .subscribe(() ->{} ,throwable -> Log.e(TAG, "Error msg", throwable))); 

我实施方式有误吗?

推荐答案

根据文档.如果@Insert方法仅接收1个参数，则它可以返回long，它是插入项的新rowId.如果参数是数组或集合，则应返回long []或List.由于您仅插入一项，因此该方法将仅返回一个rowID.

According to docs. If the @Insert method receives only 1 parameter, it can return a long, which is the new rowId for the inserted item. If the parameter is an array or a collection, it should return long[] or List instead. Since you insert only one item, the method will return only one rowID.

所以，尝试这个

Single.fromCallable(new Callable<Long>() {
        @Override
        public Long call() throws Exception {
           return productDao.insertProduct(new Product()));
        }
    })
    .subscribe(id -> {

    } ,throwable -> Log.e(TAG, "Error msg", throwable)))

您也可以使用 Observable 或 Maybe .但是我认为 Single 更合适，因为在您的情况下，id是自动生成的，插入应始终完成.

You could use Observable or Maybe as well. But I think Single fits better since in your case the id is autogenerated and the insertion should always complete.

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