java - 如何在recyclerview中显示图片？

Question

These are the list of pictures i want from database我有一个 firebase 数据库，我从中获取图像列表并将其显示在 recyclerview 中。我能够获取所有图像的 url，但无法在 ImageView 中显示图像。

 private void getImagesFromDatabase() {
    Log.d("hh", "Reach Here");
    //   String  USERID = FirebaseAuth.getInstance().getCurrentUser().getPhoneNumber();

    final DatabaseReference historyDatabase = FirebaseDatabase.getInstance().getReference().child("BeautyCenters").child(nameofspa).child("Images");
    historyDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot pictures : dataSnapshot.getChildren()) {
                Log.d("SPAA", "pictures  ARE" + pictures);
                Log.d("SPAA", "data  ARE " + dataSnapshot);
                ImagesObject imagesObject = pictures.getValue(ImagesObject.class);
                uploads.add(imagesObject);
            }
            imagesAdapter = new ImagesAdapter(DetailsPage.this, uploads);
            logorecylerview.setAdapter(imagesAdapter);
}
        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });
}

我已经尝试过这段代码，但这给了我错误 com.google.firebase.database.DatabaseException: Can't conversion object of type java.lang.String to type .DetailsPage.ImagesObject。

这是我的 ADPATER 类

public class ImagesAdapter extends  RecyclerView.Adapter<ImagesAdapter.ViewHolder> {
    private List<ImagesObject> mUploads;
    private Context mcontext;
    private LayoutInflater mInflater;
    private ImagesAdapter.ItemClickListener mClickListener;
    public ImagesAdapter(Context context, List<ImagesObject> uploads) {
       this. mcontext = context;
       this. mUploads = uploads;
        this.notifyDataSetChanged();
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        this.mInflater = LayoutInflater.from(mcontext);

        View view = mInflater.inflate(R.layout.picturesofspa, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        ImagesObject imagesObject = mUploads.get(position);
        Picasso.get()
                .load(imagesObject.getImages())
                .placeholder(R.drawable.testsaloon)
                .error(R.drawable.ic_launcher_background)
                .into(holder.PicturesofSPA);

    }

    public class ViewHolder extends RecyclerView.ViewHolder  implements View.OnClickListener {

        public ImageView PicturesofSPA;

        public ViewHolder(View itemView) {
            super(itemView);
            PicturesofSPA = (ImageView) itemView.findViewById(R.id.PicturesofSPA);

            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View v) {
        }
    }

    public interface ItemClickListener {
        void onItemClick(View view, int position);
    }

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

这是我的对象类:

public class ImagesObject {
    private String Images;

    public ImagesObject(String Images) {
        this.Images = Images;
    }

public ImagesObject() {
}
    //Images
    public String getImages(){
        return Images;
    }
    public void setImages(String Images)
    {
        this.Images = Images;
    }
}

这是我获取 URL 的位置:

private List<ImagesObject> uploads;
        uploads = new ArrayList<>();

 private void getImagesFromDatabase() {
        Log.d("hh", "Reach Here");
        //   String  USERID = FirebaseAuth.getInstance().getCurrentUser().getPhoneNumber();

        final DatabaseReference historyDatabase = FirebaseDatabase.getInstance().getReference().child("BeautyCenters").child(nameofspa).child("Images");
        historyDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot pictures : dataSnapshot.getChildren()) {
                    Log.d("SPAA", "pictures  ARE" + pictures);
                    Log.d("SPAA", "data  ARE " + dataSnapshot);

                    ImagesObject imagesObject = pictures.getValue(ImagesObject.class);
                    uploads.add(imagesObject);
                }
                imagesAdapter = new ImagesAdapter(DetailsPage.this, uploads);
                logorecylerview.setAdapter(imagesAdapter);
    }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });
    }

使用此代码，它可以计算图片数量，但不显示任何图片”

for (DataSnapshot pictures : dataSnapshot.getChildren()) {
                Log.d("SPAA", "pictures  ARE" + pictures);
                Log.d("SPAA", "data  ARE " + dataSnapshot);

                ImagesObject imagesObject = dataSnapshot.getValue(ImagesObject.class);
                uploads.add(imagesObject);
            }

Answer 1

 com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type .DetailsPage.ImagesObject

您收到上述错误是因为您的数据库中图像 url 存储为字符串。

你的数据库就像

Images:
       l0: url1
       l1: url2
       l2: url3

它应该是类 ImagesObject 类型，如下所示

Images:
      l0:
         Images: url1
      l1:
         Images: url2
      l2:
         Images: url3

为了避免该错误，请尝试以下两种解决方案:

1. 使用 ImagesObject 类将图像网址推送到实时数据库中，或者像上面那样创建数据库。

或

在您的代码中执行此操作。

String url = pictures.getValue(String.class);
ImagesObject imgObject = new ImagesObject(url);
uploads.add(imgObject);

此外，避免在 valueEventListener 内设置适配器。将适配器设置为外部，并在列表上传更改时使用 notifyDataSetChanged。也不要将 ImagesObject 中的字符串图像设为私有(private)。