我如何使用recyclerview显示图像

Question

我正在this tutorial关注如何从Firebase存储中检索上传的图像以在recyclerview中显示。但是，当我运行我的应用程序时，没有看到上传的图像，而是我的应用程序崩溃，并且错误始终指向包含此代码ImageUploadInfo imageUploadInfo = postSnapshot.getValue(ImageUploadInfo.class);的特定行，但并未真正解释其原因。我不确定有人会发生什么...请您帮我，这整整一周我一直在寻找答案，但没有得到任何答案。谢谢前进

错误：

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

适配器类别：

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;
    }
}

这是主页：

    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

像这样更改模型类，看看是否适合您。将其标记为私有会使firebase仅找到getter / setter，并在命名时尝试遵守camelCase的Java约定。

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
    }
}

关于适配器问题。您需要从MainThread进行设置，因此，从onDataChange方法中移动行

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

到您的活动的onCreate()方法，并且在onDataChange中添加到使用list = new ArrayList<>();初始化的列表后，仅使用

adapter1.notifyDataSetChanged

让我知道这是否能够解决您的问题。