如何查看 RecyclerView 项目 倒序排列最新项目在顶部

Question

如何查看 RecyclerView 顶部的最新项目？你能告诉我代码吗？

ImagesActivity.java

这是ImagesActivity我的项目的 Java 代码。您能告诉我如何RecyclerView以相反的顺序查看项目，即最新项目位于顶部吗？

public class ImagesActivity extends AppCompatActivity {
  private RecyclerView mRecyclerView;
  private ImageAdapter mAdapter;
  private ProgressBar mProgressCircle;
  private DatabaseReference mDatabaseRef;
  private List<Upload> mUploads;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_images);
    mRecyclerView = findViewById(R.id.recycler_view);
    mRecyclerView.setHasFixedSize(true);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    mProgressCircle = findViewById(R.id.progress_circle);
    mUploads = new ArrayList<>();
    mDatabaseRef = FirebaseDatabase.getInstance().getReference("uploads");
    mDatabaseRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                Upload upload = postSnapshot.getValue(Upload.class);
                mUploads.add(upload);
            }
            mAdapter = new ImageAdapter(ImagesActivity.this, mUploads);
            mRecyclerView.setAdapter(mAdapter);
            mProgressCircle.setVisibility(View.INVISIBLE);
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            Toast.makeText(ImagesActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
            mProgressCircle.setVisibility(View.INVISIBLE);
        }
    });
}
}

ImageAdapter.java

这是我的项目的 Adapter Java 类。

public class ImageAdapter extends RecyclerView.Adapter<ImageAdapter.ImageViewHolder> {
  private Context mContext;
  private List<Upload> mUploads;

  public ImageAdapter(Context context, List<Upload> uploads) {
    mContext = context;
    mUploads = uploads;
  }
  @Override
  public ImageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(mContext).inflate(R.layout.image_item, parent, false);
    return new ImageViewHolder(v);
  }
  @Override
  public void onBindViewHolder(ImageViewHolder holder, int position) {
    Upload uploadCurrent = mUploads.get(position);
    holder.textViewName.setText(uploadCurrent.getName());
    Picasso.with(mContext)
            .load(uploadCurrent.getImageUrl())
            .placeholder(R.mipmap.ic_launcher)
            .fit()
            .centerCrop()
            .into(holder.imageView);
  }
  @Override
  public int getItemCount() {
    return mUploads.size();
  }
  public class ImageViewHolder extends RecyclerView.ViewHolder {
    public TextView textViewName;
    public ImageView imageView;
    public ImageViewHolder(View itemView) {
        super(itemView);
        textViewName = itemView.findViewById(R.id.text_view_name);
        imageView = itemView.findViewById(R.id.image_view_upload);
    }
  }
}

Answer 1

从这里可以清楚地看出，您正在使用 private 绑定视图。List<Upload> mUploads; 您所需要做的就是使用以下简单的代码反转此列表：

ArrayList<ModelNAme> list = getList();
Collections.reverse(list);