使用占位符以动态值查询房间 [英] Room query with dynamic values using placeholders

问题描述

我正在实现一个Room数据库(因为我想离开装载机)，并且我有一个查询，该查询根据IN运算符选择对象:

I am implementing a Room database (because I want to move away from Loaders) and I have a query that selects objects based on the IN operator:

@Query(SELECT * FROM table WHERE icon IN(:icons))
LiveData<List<Result>> getResults(String[] icons);

问题在于:icons数组是在运行时动态生成的，首先我为其生成占位符，然后将其替换为值，如下所示:

The issue is that the :icons array is generated dynamically during runtime, first I generate placeholders for it and then replace them with the values, like so:

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    String[] iconsArray = generateIconArray();
    mViewModel = ViewModelProviders.of(this, new MyViewModelFactory(getActivity().getApplication(), iconsArray)).get(MyViewModel.class);
    mViewModel.getResults().observe(this, new Observer<List<Result>>() {
        @Override
        public void onChanged(@Nullable List<Result> results) {
            RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getActivity(), 3);
            mRecyclerView.setLayoutManager(layoutManager);
            GridAdapter adapter = new GridAdapter(getActivity(), results);
            mRecyclerView.setAdapter(adapter);
        }
    });
}

问题是我收到一个空的RecyclerView，但是当我传递带有单个图标的数组时，查询正常运行.
无法在Room中实现相同的功能，因为它会在编译时检查查询吗?
如果没有，我应该在存储库构造函数中使用db.query(...)代替它吗?

The problem is that I receive an empty RecyclerView, but when I pass an array with a single icon, the query works normally.
Is it not possible to achieve the same in Room because it checks queries during compile time?
And if not, instead of that should I just use db.query(...) in my repository constructor?

我知道在此处这类问题a>，但是它也说他们正在研究它，我找不到任何迹象.

I know this sort of question was asked here, but it also says that they are working on it, and I couldn't find any signs of it.

如果有人偶然发现了这个问题，在实现此功能时我犯了一个小错误，onActivityCreated中提供的代码实际上可以正常工作.还值得一提的是，它可用于String[]和列表，但不能用于单个字符串:"ab,cd,ef".

In case someone stumbles upon this question, I made a small mistake while implementing this feature, the code provided in onActivityCreated actually works. It's also worth mentioning that it works with String[] and lists, but not with a single string: "ab,cd,ef".

推荐答案

在实现此功能时，我犯了一个小错误，onActivityCreated中提供的代码确实有效.还值得一提的是，它可以与String[]和List一起使用，但不能与单个String:"ab，cd，ef"一起使用，这是我的错误.

I made a small mistake while implementing this feature, the code provided in onActivityCreated actually works. It's also worth mentioning that it works with String[] and List, but not with a single String: "ab,cd,ef", which was my mistake.

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