将图像从 firebase 检索到 StaggeredGridLayout Android

Posted 2023-05-07

【中文标题】将图像从 firebase 检索到 StaggeredGridLayout Android

【英文标题】：Retrieving images from firebase into a StaggeredGridLayout Android

【发布时间】：2021-06-30 03:44:11

【问题描述】：

我正在尝试将图像从 firebase 获取到 StaggeredGridLayout 中，这是一个片段，但出现了一些我无法解决的错误

错误：不兼容的类型：无法推断 ArrayList 的类型参数 postItem = new ArrayList(); ^ 原因：不存在类型变量 E 的实例，因此 ArrayList 符合 PostItem 其中 E 是类型变量： E 扩展类 ArrayList 中声明的 Object

从 android studio 获得一些建议后，我实现了一些方法，然后我得到了错误，但在我的片段中看不到应该显示的图像

这里是 JAVA 文件

Home_Fragment.java // 发生错误的地方

public class Home_Fragment extends Fragment 
    private DatabaseReference databaseReference;
    private PostItem postItem;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) 
        View view = inflater.inflate(R.layout.fragment_home, container, false);
        getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        databaseReference = FirebaseDatabase.getInstance().getReference("uploads");
        postItem = new PostItem();

        RecyclerView postRecyclerView = view.findViewById(R.id.postRecyclerView);
        postRecyclerView.setLayoutManager(
                new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL)
        );
        //this 1st error
        postItem = new ArrayList<>();
        //this 2nd error
        PostAdapter postsAdapter = new PostAdapter(postItem);
        //end


        postRecyclerView.setAdapter(postsAdapter);

        //This are images that i tried manually and it worked fine 

//        List<PostItem> postItems = new ArrayList<>();
//        postItems.add(new PostItem(R.drawable.image1));
//        postItems.add(new PostItem(R.drawable.image2));
//        postItems.add(new PostItem(R.drawable.image3));
//        postItems.add(new PostItem(R.drawable.image4));
//        postItems.add(new PostItem(R.drawable.image5));
//        postItems.add(new PostItem(R.drawable.image7));
//        postItems.add(new PostItem(R.drawable.image9));
//        postItems.add(new PostItem(R.drawable.image10));
//        postItems.add(new PostItem(R.drawable.image11));
//        postItems.add(new PostItem(R.drawable.image13));
//        postItems.add(new PostItem(R.drawable.image14));
//        postItems.add(new PostItem(R.drawable.image15));
//        postItems.add(new PostItem(R.drawable.image16));
//        postItems.add(new PostItem(R.drawable.image17));
//        postItems.add(new PostItem(R.drawable.image18));
//        postItems.add(new PostItem(R.drawable.image20));
//        postItems.add(new PostItem(R.drawable.image21));
//        postItems.add(new PostItem(R.drawable.image22));
//        postItems.add(new PostItem(R.drawable.image23));
//        postItems.add(new PostItem(R.drawable.image24));
//        postItems.add(new PostItem(R.drawable.image25));
//        postItems.add(new PostItem(R.drawable.image26));
//        postItems.add(new PostItem(R.drawable.image27));
//        postItems.add(new PostItem(R.drawable.image29));
//        postItems.add(new PostItem(R.drawable.image30));
//        postItems.add(new PostItem(R.drawable.image31));
//        postItems.add(new PostItem(R.drawable.image32));
//        postItems.add(new PostItem(R.drawable.image33));
//        postItems.add(new PostItem(R.drawable.image34));
//        postItems.add(new PostItem(R.drawable.image35));
//        postItems.add(new PostItem(R.drawable.image36));
//        postItems.add(new PostItem(R.drawable.image37));
//        postItems.add(new PostItem(R.drawable.image38));
//        postItems.add(new PostItem(R.drawable.image39));
//        postItems.add(new PostItem(R.drawable.image42));
//        postItems.add(new PostItem(R.drawable.harry1));
//        postItems.add(new PostItem(R.drawable.harry2));
//        postItems.add(new PostItem(R.drawable.harry3));
//        postItems.add(new PostItem(R.drawable.harry4));
//        postItems.add(new PostItem(R.drawable.harry5));
//        postItems.add(new PostItem(R.drawable.harry6));
//        postItems.add(new PostItem(R.drawable.harry7));
//        postItems.add(new PostItem(R.drawable.harry8));
//        postItems.add(new PostItem(R.drawable.harry9));
//        postItems.add(new PostItem(R.drawable.harry10));
//        postItems.add(new PostItem(R.drawable.harry11));
//        postItems.add(new PostItem(R.drawable.harry12));
//        postItems.add(new PostItem(R.drawable.harry13));
//        postItems.add(new PostItem(R.drawable.harry14));
//        postItems.add(new PostItem(R.drawable.harry15));

        databaseReference.addValueEventListener(new ValueEventListener() 
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) 

                for (DataSnapshot dataSnapshot : snapshot.getChildren()) 
                    PostItem postItem = dataSnapshot.getValue(PostItem.class);
                    postItem.getImage();
                

                //notify the adapter
                postsAdapter.notifyDataSetChanged();
            

            @Override
            public void onCancelled(@NonNull DatabaseError error) 

            
        );
        return view;
    

PostAdapter.java

 public class PostAdapter extends RecyclerView.Adapter<PostAdapter.PostViewHolder> 
        public final List<PostItem> postItems;
    
        public PostAdapter(List<PostItem> postItems) 
            this.postItems = postItems;
        
    
    
        @NonNull
        @Override
        public PostViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) 
            return new PostViewHolder(
                    LayoutInflater.from(parent.getContext()).inflate(
                            R.layout.post_item_container,
                            parent,
                            false
                    )
            );
        
    
        @Override
        public void onBindViewHolder(@NonNull PostViewHolder holder, int position) 
            holder.setPostImage(postItems.get(position));
    
        
    
        @Override
        public int getItemCount() 
            return postItems.size();
        
    
        static class PostViewHolder extends RecyclerView.ViewHolder 
            RoundedImageView postImageView;
    
            PostViewHolder(@NonNull View itemView) 
                super(itemView);
                postImageView = itemView.findViewById(R.id.imagePost);
            
    
            void setPostImage(PostItem postItem) 
                postImageView.setImageResource(postItem.getImage());
    
            
        
    


PostItems.java

    public class PostItem 
        private int image = 0;
    
        public PostItem(int image) 
            this.image = image;
        
    
        public PostItem() 
            return;
    
        
    
        public int getImage() 
            return image;
        
    
        public int getPit() 
            return getPit();
        
    

Upload_Fragment.java //这个Fragment是我用来上传图片到firebase的

 public class Upload_Fragment extends Fragment 
        private static final int PICK_IMAGE_REQUEST = 10;
        private Button choseImageButton;
        private Button uploadImageButton;
        private ImageView uploadImageView;
        private Uri imageUri;
        private FirebaseStorage storage;
        private StorageReference storageReference;
        private DatabaseReference databaseReference;
        private StorageTask mUploadTask;
    
        @Nullable
        @Override
        public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) 
            View view = inflater.inflate(R.layout.fragment_upload, container, false);
            Button chooseImageButton = view.findViewById(R.id.upload_image_button);
            Button uploadImageButton = view.findViewById(R.id.done_button);
            uploadImageView = view.findViewById(R.id.upload_image_view);
            storage = FirebaseStorage.getInstance();
            storageReference = storage.getReference("uploads");
            databaseReference = FirebaseDatabase.getInstance().getReference("uploads");
            chooseImageButton.setOnClickListener(new View.OnClickListener() 
                @Override
                public void onClick(View v) 
                    openFileChooser();
    
                
            );
            uploadImageButton.setOnClickListener(new View.OnClickListener() 
                @Override
                public void onClick(View v) 
                    if (mUploadTask != null && mUploadTask.isInProgress()) 
                        Toast.makeText(getActivity(), "Upload in Progress", Toast.LENGTH_SHORT).show();
    
                     else 
                        uploadToFirebase();
                    
    
    
                
            );
    
            return view;
        
    
        private void openFileChooser() 
            Intent intent = new Intent();
            intent.setType("image/*");
            intent.setAction(Intent.ACTION_GET_CONTENT);
            startActivityForResult(intent, PICK_IMAGE_REQUEST);
        
    
        @Override
        public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) 
            super.onActivityResult(requestCode, resultCode, data);
            if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK
                    && data != null && data.getData() != null) 
                imageUri = data.getData();
                Glide.with(this).load(imageUri).into(uploadImageView);
    
            
        
    
        private String getFileExtension(Uri uri) 
    
            ContentResolver contentResolver = getActivity().getContentResolver();
            MimeTypeMap mime = MimeTypeMap.getSingleton();
            return mime.getExtensionFromMimeType(contentResolver.getType(uri));
        
    
        private void uploadToFirebase() 
            if (imageUri != null) 
                final ProgressDialog progressDialog = new ProgressDialog(getActivity());
                progressDialog.setTitle("Uploading...");
                progressDialog.show();
    
                StorageReference ref = storageReference.child(System.currentTimeMillis()
                        + "." + getFileExtension(imageUri));
                mUploadTask = ref.putFile(imageUri)
                        .addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() 
                            @Override
                            public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) 
                                progressDialog.dismiss();
                                Toast.makeText(getActivity(), "Saved Succesfully", Toast.LENGTH_SHORT).show();
                                Upload_Image upload_image = new Upload_Image(ref.getDownloadUrl().toString());
                                String uploadId = databaseReference.push().getKey();
                                databaseReference.child(uploadId).setValue(upload_image);
                            
                        )
                        .addOnFailureListener(new OnFailureListener() 
                            @Override
                            public void onFailure(@NonNull Exception e) 
                                progressDialog.dismiss();
                                Toast.makeText(getActivity(), "Error Ocurred" + e.getMessage(), Toast.LENGTH_SHORT).show();
                            
                        )
                        .addOnProgressListener(new OnProgressListener<UploadTask.TaskSnapshot>() 
                            @Override
                            public void onProgress(UploadTask.TaskSnapshot taskSnapshot) 
                                double progress = (100.0 * taskSnapshot.getBytesTransferred() / taskSnapshot
                                        .getTotalByteCount());
                                progressDialog.setMessage("Uploaded " + (int) progress + "%");
                            
                        );
            
        
    
    

上传_Image.java

公共类 Upload_Image 私有字符串 mimageUrl;

public Upload_Image() 



public Upload_Image(String imageUrl) 
    mimageUrl = imageUrl;


public String getimageUrl() 
    return mimageUrl;


public void setImageUrl(String imageUrl) 
    mimageUrl = imageUrl;

【问题讨论】：

如果您遇到问题，最好在发布问题时创建MCVE。您为此问题发布了近 450 行代码。人们需要解析和尝试在线调试的内容很多。请编辑您的问题并隔离问题，这样可以增加获得帮助的机会。

好的，感谢您帮助我如何在 SO 中正确添加问题

请查看How do I ask a good question?。

【参考方案1】：

postItem 变量的引用类型是 PostItem 但您正在分配 ArrayList() 对象。您应该将引用类型更改为 List 类型。请参考以下代码。

Home_Fragment.java

private List<PostItem> postItem;

postItem = new ArrayList<>();
PostAdapter postsAdapter = new PostAdapter(postItem);

【讨论】：

我实施了您所说的更改，错误消失了，但我只看到黑色背景而不是图像

@SagarRawal 您是否正确地从 Firebase 存储中检索图像？

【参考方案2】：

在您的家庭片段中。

private ArrayList<PostItem> itemsList;

itemsList= new ArrayList<>();
PostAdapter postsAdapter = new PostAdapter(itemsList);

在你的事件监听器中，

    for (DataSnapshot dataSnapshot : snapshot.getChildren()) 
            PostItem postItem = dataSnapshot.getValue(PostItem.class);
            itemsList.add(postItem.getImage());
          

您没有将任何图像添加到列表中，因此您什么也得不到。