Java 如何调用Firebase Realtime Database中的子图像列表到android studio中的回收器视图

如果您想使用Java在Android上的RecylerView中显示这些URL，请执行以下步骤:

在build.grade FILE模块文件中添加以下依赖项:

implementation("com.github.bumptech.glide:glide:4.16.0")
implementation("androidx.cardview:cardview:1.0.0")

创建一个包含RecyclerView的.XML文件:

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

for each 图像创建布局:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    app:cardCornerRadius="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="200dp">

            <ImageView
                android:id="@+id/image_view"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:scaleType="centerCrop"
                android:contentDescription="@null"/>
        </FrameLayout>
    </LinearLayout>
</android.support.v7.widget.CardView>

创建一个适配器类:

public class UrlsAdapter extends RecyclerView.Adapter<UrlsAdapter.UrlViewHolder> {
    private Context context;
    private List<String> urls;

    public UrlsAdapter(Context context, List<String> urls) {
        this.context = context;
        this.urls = urls;
    }

    @NonNull
    @Override
    public UrlViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
        View view = LayoutInflater.from(context).inflate(R.layout.image_layout, parent, false);
        return new UrlViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull UrlViewHolder urlViewHolder, int position) {
        String url = urls.get(position);
        urlViewHolder.bind(url);
    }

    @Override
    public int getItemCount() {
        return urls.size();
    }

    class UrlViewHolder extends RecyclerView.ViewHolder {
        View itemView;
        ImageView imageView;

        UrlViewHolder(View itemView) {
            super(itemView);
            this.itemView = itemView;
            imageView = itemView.findViewById(R.id.image_view);
        }

        void bind(String url) {
            Glide.with(context).load(url).into(imageView);
        }
    }
}

在Activity中创建一个List类型的全局变量:

List<String> urls = new ArrayList<>();

在Activity中找到RecyclerView并创建适配器:

RecyclerView recyclerView = findViewById(R.id.recycler_view);
UrlsAdapter urlsAdapter = new UrlsAdapter(this, urls);
recyclerView.setAdapter(urlsAdapter);

从实时数据库中获取urls并通知适配器:

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference db = FirebaseDatabase.getInstance().getReference();
DatabaseReference imageUrlsRef = db.child("Listings").child(uid).child("imageUrls");
imageUrlsRef.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if (task.isSuccessful()) {
            for (DataSnapshot ds : task.getResult().getChildren()) {
                String url = ds.getValue(String.class);
                urls.add(url);
            }
            urlsAdapter.notifyDataSetChanged();
        } else {
            Log.d(TAG, task.getException().getMessage()); //Never ignore potential errors!
        }
    }
});

现在，您应该看到一个RecyclerView，它在Glide库的帮助下显示图像列表.