如何使用 recyclerview 顯示圖像

Question

我正在關注有關如何從 Firebase 存儲檢索上傳的圖像以在 recyclerview 中顯示的教程。 但是當我運行我的應用程序時，我沒有看到上傳的圖像，而是我的應用程序崩潰了，並且錯誤一直指向包含此代碼的特定行ImageUploadInfo imageUploadInfo = postSnapshot.getValue(ImageUploadInfo.class); 但它並沒有真正解釋為什么它是一個錯誤。 我不確定這是怎么回事，有人可以嗎...請幫助我我整個星期都在尋找有關此問題的答案，但沒有得到任何答案。 感謝提前

錯誤：

FATAL EXCEPTION: main
Process: com.myapp.Gogo, PID: 22974
com.google.firebase.database.DatabaseException: Found two getters or fields 
with conflicting case sensitivity for property: imageurl

2020-03-05 11:06:36.238 22974-22974/com.myapp.Gogo
E/RecyclerView: No adapter attached; skipping layout

適配器類：

public class AdapterOne extends RecyclerView.Adapter<AdapterOne.ViewHolder> {
    Context context;
    List <ImageUploadInfo> ImageUploadInfoList;

    public AdapterOne(Context c, List<ImageUploadInfo> TempList){
        this.ImageUploadInfoList=TempList;
        this.context=c;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view=LayoutInflater.from(parent.getContext()).inflate(R.layout.cardview,parent,false);
        ViewHolder viewHolder=new ViewHolder(view);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        ImageUploadInfo imageUploadInfo=ImageUploadInfoList.get(position);

        //loading image with glide libary
        Glide.with(context).load(imageUploadInfo.getImageUrl()).into(holder.imageView);
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {

        public ImageView imageView;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            imageView=(ImageView) itemView.findViewById(R.id.imageview);
        }
    }
}

ImageUpload.class:

public class ImageUploadInfo {
    public String imageURL;

    public ImageUploadInfo( String url) {
        //this.imageName = name;
        this.imageURL= url;
    }

    public String getImageUrl() {
        return null;
    }
}

這是主頁面：

    if(firebaseUser!=null) {
        String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
        DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference("Users");
        DatabaseReference uidRef = rootRef.child("images").child(uid);

        uidRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                    ImageUploadInfo imageUploadInfo = postSnapshot.getValue(ImageUploadInfo.class);
                    list.add(imageUploadInfo);
                }

                adapter1 = new AdapterOne(getApplicationContext(), list);
                recyclerView.setAdapter(adapter1);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {}
        });
    }

Answer 1

像這樣更改您的模型類，看看這是否適合您。 將其標記為私有會使 firebase 只找到 getter/setter 並在命名時嘗試遵守camelCase 的Java 約定。

public class ImageUploadInfo {

    private String imageUrl; // main change is this should be private

    private ImageUploadInfo() {} // default constructor that takes no arguments

    public ImageUploadInfo(String imageUrl) {
        this.imageUrl= imageUrl;
    }

    public String getImageUrl() {
        return imageUrl;  // and why are you returning null here
    }
}

對於適配器問題。 您需要從 MainThread 設置它，因此，從您的onDataChange方法移動行

adapter1 = new AdapterOne(getApplicationContext(), list);
recyclerView.setAdapter(adapter1);
adapter1.notifyDataSetChanged;

到您的活動的onCreate()方法，並在添加到使用list = new ArrayList<>();初始化的list = new ArrayList<>();后在onDataChange list = new ArrayList<>(); 只使用

adapter1.notifyDataSetChanged

讓我知道這是否能夠解決您的問題。