从sqlite获取的数据未显示在recyclerview中

Question

    messageList = (RecyclerView) findViewById(R.id.message_list);
    mRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_refresh_layout);
    linearLayoutManager = new LinearLayoutManager(getApplicationContext());

    messageList.setLayoutManager(linearLayoutManager);

    mAdapter = new MessagesAdapter(messages);
    messageList.setAdapter(mAdapter);

final MainData mHelper = new MainData(this);
    final Cursor csr = mHelper.getAllQuestions3();
            sqlite = mDatabaseReference.child("Messages").child(MessageSenderId).child(MessageRecieverId);
            valueEventListener = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot ds : dataSnapshot.getChildren()) {

//I add the data from firebase to SQLITE here 


                while (csr.moveToNext()) {
                    String mSender = csr.getString(csr.getColumnIndex(KEY_SENDER));
                    String mMessage = csr.getString(csr.getColumnIndex(KEY_MESSAGE));
                    long mTime = csr.getLong(csr.getColumnIndex(KEY_TIME));
                    String mSeen = csr.getString(csr.getColumnIndex(KEY_SEEN));
                    String mTimer = csr.getString(csr.getColumnIndex(KEY_TIMER));
                    String mType = csr.getString(csr.getColumnIndex(KEY_TYPE));

                    messages.add(new SQLiteHelper(mSender, mMessage, mType, mSeen, mTimer, mTime));
                    mAdapter.notifyDataSetChanged();
                }
                    mDatabaseReference.child("Messages").child(MessageSenderId).child(MessageRecieverId).setValue(null);

        }
            @Override
            public void onCancelled(DatabaseError databaseError) {
        }
    };
            sqlite.addListenerForSingleValueEvent(valueEventListener);

适配器

public class MessagesAdapter extends RecyclerView.Adapter<MessagesAdapter.MessageViewHolder>{
ChatData mHelper;
Cursor csr;
private List<SQLiteHelper> mMessagesHelperList;
private FirebaseAuth mAuth;


public MessagesAdapter(List<SQLiteHelper> MessagesHelperList) {
    this.mMessagesHelperList = MessagesHelperList;
}


public class MessageViewHolder extends RecyclerView.ViewHolder{
    public TextView messageText;


    public MessageViewHolder(View view) {
        super(view);
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(view.getContext());


        mHelper = new ChatData(view.getContext(),"MessagePlus",null,1);
        csr = mHelper.getAllQuestions3();

        messageText = (TextView)view.findViewById(R.id.message_text_layout);
    }
}

@Override
public MessageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View V = LayoutInflater.from(parent.getContext()).inflate(R.layout.custom_activity_chat,parent,false);
    mAuth = FirebaseAuth.getInstance();
    return new MessageViewHolder(V);
}

@Override
public void onBindViewHolder(final MessageViewHolder holder, int position) {
    SQLiteHelper messagesHelper = mMessagesHelperList.get(position);

       holder.messageText.setText(messagesHelper.getMessage());
    }

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

我有另一个活动，我获取sqlite数据并在recyclerview中显示它，它工作，我已经实现了与此相同的方式。这里它曾经工作，但后来我添加了一些功能，并移动了一些代码，现在它不工作，我已经多次检查整个代码，但仍然没有找到为什么它不工作...

表和行存在数据，列表的大小也不为空

刚发现当我在其中添加Logs时，不会调用Adapter。多数民众赞成在哪里问题，但idk为什么

Answer 1

您的问题是您将额外的消息添加到您首次创建适配器的列表中

代替

messages.add(new SQLiteHelper(mSender, mMessage, mType, mSeen, mTimer, mTime));
mAdapter.notifyDataSetChanged();

做

mAdapter.add(new SQLiteHelper(mSender, mMessage, mType, mSeen, mTimer, mTime));

在你的适配器中，你必须添加这样的添加功能

public void add(SQLiteHelper item){
    if(mMessagesHelperList!=null){
        mMessagesHelperList.add(item);
        notifyDataSetChanged();
    }
}

也

你的代码上有太多“垃圾”，你在ValueEventListener上试图读取游标的值而不是ds（DataSnapshot）。所以你的光标可能是空的。如果光标为空，则不向适配器添加任何项，因此适配器没有要显示的项，因此onBindViewHolder无法正确调用