在Firebase Recycler适配器中仅加载x个项目 [英] Load only x items in Firebase Recycler Adapter

问题描述

我有一个Firebase FirebaseRecyclerAdapter，在数据库的Firebase项目中，我有30多个值，在我的应用中，我只想显示前x个项目.

Hi so I have one Firebase FirebaseRecyclerAdapter and in my Firebase project in my database I have over 30 values and in my app I want to display only the first x items.

我在互联网上进行搜索，但是找不到如何只能加载x项的内容.

I searched on internet but I didn't find how I could load only x items.

这是我的代码:

        mAdapter = new FirebaseRecyclerAdapter<Post, Holder>(
            Post.class,
            R.layout.item_layout,
            Holder.class,
            mRef
    ){

        @Override
        public void onBindViewHolder(Holder viewHolder, int position) {
            Post post = (Post) this.getItem(position);
            ((Holder) viewHolder).bind(post);

        }
        @Override
        public Holder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater inflater = LayoutInflater.from(parent.getContext());
            View view;
            view = inflater.inflate(R.layout.item_layout , parent, false);
            return new Holder(view);
        }
 }

这是我的持班人:

public static class EventsOldHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    public EventsOldHolder(View itemView) {

    }
    public void bind(final Post post) {
    }
    @Override
    public void onClick(View view) {
    }

我知道，当position的值大于x时，我可以隐藏元素，但是如果我有很多项目并隐藏所有元素，则我的应用程序运行速度会变慢，并且如果可以帮助我提供更好的解决方案. >

I know I can hide the elements when position has a higher value than x but if I have a lot of items and hide all of them my app will work slower and if you can help me with a better solution.

推荐答案

要解决此问题，您应该将query而不是mRef传递给FirebaseRecyclerAdapter构造函数，我认为它是DatabaseReference对象

To solve this, you should pass to the FirebaseRecyclerAdapter constructor a query instead of the mRef, which I assume is a DatabaseReference object.

假设您具有一个如下所示的数据库结构:

Assuming that you have a database structure that looks like this:

Firebase-root
    |
    --- posts
          |
          --- postId
                |
                --- title: "Post Title"
                |
                --- //Other details

要仅显示前5个项目，查询应如下所示:

To display only the first 5 items, the query should look like this:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRef.child("posts").orderByChild("title").limitToFirst(5);
query.addListenerForSingleValueEvent(/* ... */);

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