Question

我有一个涉及到消息传递人员的应用程序，每当我从childeventlistener加载一条消息以将其添加到列表视图时，列表视图中的消息/对象就会出现两次，我看不出是什么导致了这种情况？每次发送消息时，我都会调用一个将其添加到适配器的方法，然后使用notifiyDataSetChanged（）方法将其添加到列表视图中，就好像它是普通的消息传递应用程序一样。

我的聊天活动：

chatURLRoot.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                append_chat_conversation(dataSnapshot);
            }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {
                //append_chat_conversation(dataSnapshot);
            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

    }

    public String chat_msg, chat_username;

    private void append_chat_conversation(DataSnapshot dataSnapshot) {
        for (DataSnapshot ds : dataSnapshot.getChildren()) {
            Log.e("Chat details: ", String.valueOf(ds));
            chat_username = dataSnapshot.child("username").getValue(String.class);
            chat_msg = dataSnapshot.child("message").getValue(String.class);

            Chat chat = new Chat(chat_username, chat_msg);
            chatList.add(chat);
            Log.e("Chat username: ", "" + chat_username);
            Log.e("Chat message: ", "" + chat_msg);
        }
        adapter.notifyDataSetChanged();
    }

chatListAdapter：

public class chatListAdapter extends ArrayAdapter<Chat> {

    private Context mContext;
    int mResource;
    TextView usernameTV, messageTV;

    public chatListAdapter(Context context, int resource, ArrayList<Chat> objects) {
        super(context, resource, objects);
        mContext = context;
        mResource = resource;

    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        String username = getItem(position).getUsername();
        String message = getItem(position).getMessage();

        Chat chat = new Chat(username, message);

        LayoutInflater inflater = LayoutInflater.from(mContext);
        convertView = inflater.inflate(mResource, parent, false);


        usernameTV = convertView.findViewById(R.id.username_chat);
        messageTV = convertView.findViewById(R.id.message_chat);

        usernameTV.setText(username);
        messageTV.setText(message);

        return convertView;
    }
}

非常感谢

内森

答案：

我只是脑子大跳，因为将值添加到列表视图的代码行在for循环中，并且需要检查两个值，所以它将运行该代码行两次！这是更新的代码，我只是把它放在了for循环中：

private void append_chat_conversation(DataSnapshot dataSnapshot) {
        for (DataSnapshot ds : dataSnapshot.getChildren()) {
            Log.e("Chat details: ", String.valueOf(ds));
            chat_username = dataSnapshot.child("username").getValue(String.class);
            chat_msg = dataSnapshot.child("message").getValue(String.class);


            Log.e("Chat username: ", "" + chat_username);
            Log.e("Chat message: ", "" + chat_msg);
        }
        Chat chat = new Chat(chat_username, chat_msg);
        chatList.add(chat);
        adapter.notifyDataSetChanged();
    }

Answer 1

这对我有用：在“我的聊天”活动中，append_chat_conversation已更改。

private void append_chat_conversation(DataSnapshot dataSnapshot) {

        chat_username = dataSnapshot.child("username").getValue(String.class);
        chat_msg = dataSnapshot.child("message").getValue(String.class);

        Chat chat = dataSnapshot.getValue(Chat.class);
        adapter.add(chat);
        Log.e("Chat username: ", "" + chat_username);
        Log.e("Chat message: ", "" + chat_msg);

    adapter.notifyDataSetChanged();
}

将Firebase中的重复值加载到ListView中

1 个答案: