如何使用Android在RecyclerView中显示Firestore中的数据？ [英] How to display data from Firestore in a RecyclerView with Android?

问题描述

使用Android在 RecyclerView 中显示现有Firestore数据库中数据的最佳方法是什么？

What is the best way to display data from an existing Firestore database in a RecyclerView using Android?

这不作为答案中的完整解释，所以我添加了这个Q& A风格，因此它可以在评论中链接。

This isn't covered as a full explanation in an answer, so I've added this Q&A-style so it can be linked to in comments.

推荐答案

假设你有一个如下所示的Firestore数据库结构：

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

Firestore-root
    |
    --- products (collection)
           |
           --- documentIdOne (document)
           |        |
           |        --- productName: "Milk"
           |
           --- documentIdTwo (document)
           |        |
           |        --- productName: "Soy Milk"
           |
           --- documentIdThree (document)
                    |
                    --- productName: "Bacon"

一个看起来像这样的模型类：

A model class that looks also like this:

public class ProductModel {
    private String productName;

    public ProductModel() {}

    public ProductModel(String productName) {this.productName = productName;}

    public String getProductName() {return productName;}
}

以及 .XML 包含 RecyclerView 的文件，如下所示：

And a .XML file that contains a RecyclerView which also looks like this:

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/recycler_view"/>

要显示所有产品名称，请按照以下步骤操作。

To display all the product names, please follow the next steps.

首先，您需要在活动中找到 RecyclerView 并设置 LinearLayoutManager ，如下所示：

First, you need to find the RecyclerView in your activity and set the LinearLayoutManager like this:

RecyclerView recyclerView = findViewById(R.id.recycler_view);
recyclerView.setLayoutManager(new LinearLayoutManager(this));

然后，您需要创建Firestore数据库的根引用和查询这样的对象：

Then you need to create the root reference of your Firestore database and a Query object like this:

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
Query query = rootRef.collection("products")
        .orderBy("productName", Query.Direction.ASCENDING);

然后你必须创建一个 FirestoreRecyclerOptions 像这样的对象：

Then you'll have to create a FirestoreRecyclerOptions object like this:

FirestoreRecyclerOptions<ProductModel> options = new FirestoreRecyclerOptions.Builder<ProductModel>()
        .setQuery(query, ProductModel.class)
        .build();

在您的活动类中，创建一个持有者看起来像这样的类：

In your activity class, create a holder class that looks like this:

private class ProductViewHolder extends RecyclerView.ViewHolder {
    private View view;

    ProductViewHolder(View itemView) {
        super(itemView);
        view = itemView;
    }

    void setProductName(String productName) {
        TextView textView = view.findViewById(R.id.text_view);
        textView.setText(productName);
    }
}

然后创建适配器声明为全局：

private FirestoreRecyclerAdapter<ProductModel, ProductViewHolder> adapter;

并在您的活动中实例化它：

And instantiate it in your activity like this:

adapter = new FirestoreRecyclerAdapter<ProductModel, ProductViewHolder>(options) {
    @Override
    protected void onBindViewHolder(@NonNull holder productViewHolder, int position, @NonNull ProductModel productModel) {
        holder.setProductName(productModel.getProductName());
    }

    @NonNull
    @Override
    public ProductViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_product, parent, false);
        return new ProductViewHolder(view);
    }
};
recyclerView.setAdapter(adapter);

最后，不要忘记覆盖以下两种方法并开始侦听更改： / p>

In the end, don't forget to override the following two methods and start listening for changes:

@Override
protected void onStart() {
    super.onStart();
    adapter.startListening();
}

@Override
protected void onStop() {
    super.onStop();

    if (adapter != null) {
        adapter.stopListening();
    }
}

结果如下：

修改：

如果您想在用户点击某个项目时显示Toast消息，请在 setProductName（）中添加以下代码行：来自 ProductViewHolder 类的方法：

If you want to display a toast message when the user clicks on an item, please add the following lines of code inside the setProductName() method from the ProductViewHolder class:

textView.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        Toast.makeText(getApplicationContext(), productName, Toast.LENGTH_SHORT).show();
    }
});

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