Android 聊天应用程序：消息适配器无法正确更新列表视图中的项目

Question

这是我在 Stack Overflow 上的第一个问题，我一直在 Android 上构建一个简单的聊天应用程序，它从在线数据库加载聊天历史记录，并将使用自定义消息适配器显示在列表视图中。

这是程序的当前状态：

Demo

但是，数组列表下第 6 条聊天消息后，列表项的布局不正确，并且后面的所有聊天消息都在重复前 6 条消息的布局。

这是我的适配器的代码：

public class messageAdapter extends ArrayAdapter<chatMessage> {

private Activity activity;
private List<chatMessage> messages;

public messageAdapter(Activity context, int resource, List<chatMessage> objects) {
    super(context, resource, objects);
    this.activity = context;
    this.messages = objects;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;
    LayoutInflater inflater = (LayoutInflater) activity.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);

    int layoutResource = 0; // determined by view type
    chatMessage chatMessage = getItem(position);
    int viewType = getItemViewType(position);

    if (chatMessage.isMine()) {
        layoutResource = R.layout.chat_bubble_right;
    } else {
        layoutResource = R.layout.chat_bubble_left;
    }

    if (convertView != null) {
        holder = (ViewHolder) convertView.getTag();
    } else {
        convertView = inflater.inflate(layoutResource, parent, false);
        holder = new ViewHolder(convertView);
        convertView.setTag(holder);
        Log.d("ViewID", "generated");
    }

    //set message content
    holder.message.setText(chatMessage.getContent());

    return convertView;
}

@Override
public int getViewTypeCount() {
    // return the total number of view types. this value should never change
    // at runtime
    return 2;
}

@Override
public int getItemViewType(int position) {
    // return a value between 0 and (getViewTypeCount - 1)
    return position % 2;
}

private class ViewHolder {
    private TextView message;

    public ViewHolder(View v) {
        message = (TextView) v.findViewById(R.id.txt_msg);
    }
}

这是我将聊天消息加载到数组列表中的方法：

private class getChatHistory extends AsyncTask<DBConnection,Long,JSONArray> {
    @Override
    protected JSONArray doInBackground(DBConnection... params) {
        return params[0].getChatHistory(userID);
    }

    @Override
    protected void onPostExecute(JSONArray jsonArray) {

        chatData = jsonArray;

        if (chatData != null)
        {
            for (int i = 0; i < chatData.length(); i++)
            {
                JSONObject currentItem = null;

                try
                {
                    currentItem = chatData.getJSONObject(i);
                    int msgID = currentItem.getInt("MessageID");
                    String currentText = currentItem.getString("MessageContent");
                    int senderID = currentItem.getInt("SenderID");
                    int receiverID = currentItem.getInt("ReceiverID");
                    chatMessage currentMessage = new chatMessage(currentText, senderID, userID);
                    Log.d("Is Mine", Boolean.toString(currentMessage.isMine()));
                    messageHistory.add(currentMessage);
                    DBAdapter.notifyDataSetChanged();

                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

这是我从我运行的 PHP 文件中获得的 JSONArray：

[{"MessageID":"1","SenderID":"1","ReceiverID":"8","Duration":"2.4","MessageContent":"agnblean liajiaj vliwv fla","MessageLength":"26","Status":"received","Date":"2016-04-04 14:00:00"},
{"MessageID":"2","SenderID":"8","ReceiverID":"1","Duration":"3.1","MessageContent":"akwuehrgeubwfcofawve","MessageLength":"20","Status":"received","Date":"2016-04-04 17:00:00"},
{"MessageID":"3","SenderID":"8","ReceiverID":"1","Duration":"3.1","MessageContent":"akwuehrgeubwfjurawve","MessageLength":"20","Status":"received","Date":"2016-04-04 17:00:05"},
{"MessageID":"4","SenderID":"8","ReceiverID":"1","Duration":"3.1","MessageContent":"akwuehrgeubwalwrawve","MessageLength":"20","Status":"received","Date":"2016-04-04 17:00:10"},
{"MessageID":"5","SenderID":"1","ReceiverID":"8","Duration":"3.1","MessageContent":"akwuehrgeubwalwrawve","MessageLength":"20","Status":"received","Date":"2016-04-04 17:01:10"},
{"MessageID":"8","SenderID":"1","ReceiverID":"8","Duration":"4.6","MessageContent":"vsjkgkgredjegwhkaga","MessageLength":"23","Status":"received","Date":"2016-04-05 05:00:00"},
{"MessageID":"9","SenderID":"8","ReceiverID":"1","Duration":"5.2","MessageContent":"agrlanwligna","MessageLength":"21","Status":"received","Date":"2016-04-06 00:00:00"},
{"MessageID":"10","SenderID":"8","ReceiverID":"1","Duration":"7.2","MessageContent":"akewgaughurawaarg","MessageLength":"12","Status":"received","Date":"2016-04-12 00:00:00"},
{"MessageID":"11","SenderID":"1","ReceiverID":"8","Duration":"7.2","MessageContent":"wgkakjrgnjange","MessageLength":"41","Status":"received","Date":"2016-04-15 00:00:00"},
{"MessageID":"12","SenderID":"1","ReceiverID":"8","Duration":"4.67","MessageContent":"yikes","MessageLength":"5","Status":"received","Date":"2016-04-21 00:00:00"},
{"MessageID":"13","SenderID":"8","ReceiverID":"1","Duration":"8.2","MessageContent":"iobanoine","MessageLength":"4","Status":"received","Date":"2016-04-30 00:00:00"}]

所以我认为这将为聊天历史记录生成正确的布局，其中活动用户是用户 ID = 1，所有发件人 ID = 1 的消息都应该在列表视图的右侧，但是相反，我得到了这个：

screenshot

这是列表视图中第 5-8 个元素的截图，但是第 7 个元素在右侧而不是在左侧，后面的元素继续重复前 6 个元素的模式。我已经检查了转换视图的日志，它只显示了 6 次，这是否与此错误有关？以及如何解决适配器无法正确定位列表项资源的问题？

编辑：我已将 getItemViewType() 的覆盖更改为此

@Override
public int getItemViewType(int position) {
    chatMessage chatMessage = getItem(position);
    if (chatMessage.isMine()) {
        return 0;
    } else {
        return 1;
    }
}

我还删除了getViewTypeCount的覆盖方法，并在getView()方法中稍微改变了条件：

int viewType = getItemViewType(position);

    if (viewType==0) {
        layoutResource = R.layout.chat_bubble_right;
    } else {
        layoutResource = R.layout.chat_bubble_left;
    }

现在聊天消息列表的顺序正常到第8个元素，然后顺序又变错了。

编辑 2

我已经跟踪日志中生成的列表项（即新项）的数量，这是我向下滚动到列表视图底部后得到的结果：

04-06 19:23:54.894 11202-11202/com.example.user.normalinterface D/ViewID: generated
04-06 19:23:54.907 11202-11202/com.example.user.normalinterface D/ViewID: generated
04-06 19:23:54.912 11202-11202/com.example.user.normalinterface D/ViewID: generated
04-06 19:23:54.914 11202-11202/com.example.user.normalinterface D/ViewID: generated
04-06 19:23:56.850 11202-11202/com.example.user.normalinterface D/ViewID: generated

这是否与我的问题有关？列表视图中的所有后续记录似乎都在重复列表中前 5 项的模式。

Answer 1

我认为它来自getViewTypeCount() 方法。在这里，您说您有 2 种不同类型的布局。使用getItemViewType() 方法，您说不同的类型是两条消息中的一条。但是您不会在 getView 方法中使用类型。

显然你不需要这两种类型，所以我建议你只删除这两种方法： getViewTypeCount() 和 getItemViewType()

我认为你不需要它们。

编辑： 您实际上需要这些方法，但是您严重覆盖了getItemViewType。

@Override
public int getItemViewType(int position) {
    chatMessage chatMessage = getItem(position);
    if (chatMessage.isMine()) {
        return 0;
    } else {
        return 1;
    }
}

Answer 2

根据我的经验，但可能与此无关，您需要在适配器中调用 notifyDataSetChanged()，因此在适配器中设置一个名为 refreshData 的方法，如下所示：

public void refreshData(ArrayList<yourList> data) {
    mValues.clear();
    mValues.addAll(data);
    notifyDataSetChanged();
}

并从您的活动中调用：

mAdapter.refreshData(newData) 

以新数据作为参数。

另外，请确保正确引用适配器类，因此请尝试添加到类的开头：

private final DBAdapter mAdapter;

然后在 getChaHistory 中添加：

mAdapter = DBAdapter

你的适配器有一个正确引用的句柄。请注意对先前答案的更改，您现在调用 mAdapter.refreshData(newData) 而不是 DBAdapter.refreshData(newdata)。真的我认为你应该将适配器传递给班级，我就是这样做的，但你可以试试这种方式，看看你的进展如何？

Answer 3

这将正常工作，但不会那么快。它决定根据值实例化哪个布局，如果“isMine()”如果“isMine() 为真，则实例化包含右对齐 TextView 的布局。否则，实例化另一个布局，（其中 TextView 左对齐)。

@Override
public View getView(int position, View convertView, ViewGroup parent){

    if(messages.get(position).isMine()){
        item = ((Activity)context).getLayoutInflater().inflate(R.layout.chat_bubble_right,null);
    }
    else{
        item = ((Activity)context).getLayoutInflater().inflate(R.layout.chat_bubble_left,null);
    }
    // set the text in the view.
    ((TextView) item.findViewById(R.id.chat_text)).setText(data.get(position).getMessage());
    return item;
}

chat_text id 指的是实例化布局中的 TextView。 （两种布局都包含一个 ID 为 chat_text 的 TextView）。
我将此 Google IO 事件用作资源：
https://www.youtube.com/watch?v=wDBM6wVEO70