Question

我在RecyclerView中遇到重复项目时遇到问题。每当我上传到我的Firebase并再次打开main活动时，recyclerView中的重复主题便会重复之前的加载。如何从recyclerView中删除重复的物品。

我的主要活动的代码是

private RecyclerView mRecyclerView;
private RecyclerViewAdapter mAdapter;

private DatabaseReference mDatabaseReference;
private List<Upload> mUploads;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_posts);
    setupBottomNavigation();

    mRecyclerView = findViewById(R.id.recycler_view);
    mRecyclerView.setHasFixedSize(true);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));



    mUploads = new ArrayList<>();


    mDatabaseReference = FirebaseDatabase.getInstance().getReference("uploads");

    mDatabaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot postSnapshot : dataSnapshot.getChildren())
            {
                Upload upload = postSnapshot.getValue(Upload.class);
                mUploads.add(upload);
            }
            mAdapter = new RecyclerViewAdapter(MainActivity.this, mUploads);
            mRecyclerView.setAdapter(mAdapter);
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Toast.makeText(MainActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
        }
    });

    Button btn_post = (Button) findViewById(R.id.post_Main);
    btn_post.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent_posts = new Intent(MainActivity.this, Posts.class);
            startActivity(intent_posts);

        }
    });

}

我的Adapter类中的代码是

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.rViewHolder> {

private Context mContext;
private List<Upload> mUploads;

public RecyclerViewAdapter(Context context, List<Upload> uploads){
    mContext = context;
    mUploads = uploads;
}

@Override
public rViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(mContext).inflate(R.layout.card_view_recycler_view, parent, false);
    return new rViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull rViewHolder viewHolder, int position) {
    Upload uploadCurrent = mUploads.get(position);
    viewHolder.textViewDescription.setText(uploadCurrent.getDescription());
    Picasso.get().load(uploadCurrent.getImageUrl()).into(viewHolder.imageView);

}

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


public class rViewHolder extends RecyclerView.ViewHolder{
    public TextView textViewDescription;
    public ImageView imageView;

    public  rViewHolder(View itemView){
        super(itemView);
        textViewDescription = itemView.findViewById(R.id.r_description);
        imageView = itemView.findViewById(R.id.r_image_view);
    }
}

Answer 1

我认为发生这种情况是因为Firebase离线存储数据，请尝试以下方式初始化实例

ps -ef | grep process_name 
if [ $? -eq 0 ]; then
  echo "Process is running."
else
  echo "Process is not running."
fi

应该工作。

Answer 2

请尝试清除列表，然后再向其中添加数据，如下所示。

private RecyclerView mRecyclerView;
private RecyclerViewAdapter mAdapter;

private DatabaseReference mDatabaseReference;
private List<Upload> mUploads;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_posts);
    setupBottomNavigation();

    mRecyclerView = findViewById(R.id.recycler_view);
    mRecyclerView.setHasFixedSize(true);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));



    mUploads = new ArrayList<>();


    mDatabaseReference = FirebaseDatabase.getInstance().getReference("uploads");

    mDatabaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot postSnapshot : dataSnapshot.getChildren())
            {
                Upload upload = postSnapshot.getValue(Upload.class);
                mUploads.clear();
                mUploads.add(upload);
            }
            mAdapter = new RecyclerViewAdapter(MainActivity.this, mUploads);
            mRecyclerView.setAdapter(mAdapter);
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Toast.makeText(MainActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
        }
    });

    Button btn_post = (Button) findViewById(R.id.post_Main);
    btn_post.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent_posts = new Intent(MainActivity.this, Posts.class);
            startActivity(intent_posts);

        }
    });

}

Answer 3

在这种情况下，请尝试清除您的ArrayList mUploads，然后再向其中添加项目，

mDatabaseReference.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        // Clear ArrayList
        mUploads.clear();
        for(DataSnapshot postSnapshot : dataSnapshot.getChildren())
        {
            Upload upload = postSnapshot.getValue(Upload.class);
            mUploads.add(upload);
        }
        mAdapter = new RecyclerViewAdapter(MainActivity.this, mUploads);
        mRecyclerView.setAdapter(mAdapter);
    }
    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Toast.makeText(MainActivity.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
    }
});

这对我而言效果很好，希望对您有所帮助。 Reference here.

Answer 4

如果您卸载应用程序并重新安装，并且安装后首次运行该应用程序时列表中有重复项，则后端Firebase中将存在重复项。如果仅在您第二次运行该应用程序时存在重复项，则您的代码负责。

您显示的代码对我来说看起来不错。可能还有一些您没有显示的错误，例如您有重复的addValueEventListener或您用List<Upload> mUploads再次喂入适配器

许多人在这里建议您不必执行mUploads.clear();，因为您是从onCreate()填充数组的，女巫在活动生命周期中仅运行一次

如果您不在其他地方使用

，我会将private List<Upload> mUploads;内的onCreate()作为局部变量移动

RecyclerView中的重复项

4 个答案: