Question

使用Oncreate方法从服务器获取聊天记录以在listview上设置的线程，代码如下：

Runnable run = new Runnable() {
        public void run() {
            // new Comments(false).execute();
            new GetChatFromServer().execute();
            handler.postDelayed(this, 1600);
        }
    };
    runOnUiThread(run);

它正在调用GetChatFromServer类以使所有最近更新的聊天记录正常工作，但问题是当我向下滚动列表视图时它会自动向上滚动。

class GetChatFromServer extends AsyncTask<String, Integer, Double> {

        String chathistory;

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();

            System.out.println("My url is>>>>" + chatHistoryUrl);
        }

        @SuppressWarnings("unchecked")
        @Override
        protected Double doInBackground(String... params)
                throws ArrayIndexOutOfBoundsException {

            ServiceHandler sh = new ServiceHandler();
            // Making a request to url and getting response
            String jsonStr = sh.makeServiceCall(chatHistoryUrl,
                    ServiceHandler.GET);
            chathistory = "{\"chatHistories\":" + jsonStr + "}";
            Gson gson = new Gson();
            Type listType = new TypeToken<List<ChatHistory>>() {
            }.getType();
            chatHistories = (ArrayList<ChatHistory>) gson.fromJson(jsonStr,
                    listType);
            // ChatModel res = gson.fromJson(chathistory, ChatModel.class);

            return null;
        }

        protected void onProgressUpdate(Integer... progress) {
            // pb.setProgress(progress[0]);
        }

        @Override
        protected void onPostExecute(Double result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            mAdapter = new ChatMessageAdapter(ChatMainActivity.this,
                    chatHistories, sourceId);
            chatList.setAdapter(mAdapter);

        }

    }

如果有人可以帮助解决我的问题。提前谢谢。

Answer 1

问题出在这里

@Override
protected void onPostExecute(Double result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);
    mAdapter = new ChatMessageAdapter(ChatMainActivity.this,
            chatHistories, sourceId);
    chatList.setAdapter(mAdapter);

}

每当您从服务器获取数据时，您一次又一次地呼叫setAdapter，您需要做的是在OnCreate中设置适配器并在您获取数据时调用mAdapter.notifyDataSetChanged。

以下是示例：

String chathistory;
ChatMessageAdapter mAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ........
    mAdapter = new ChatMessageAdapter(ChatMainActivity.this, chatHistories, sourceId);
    chatList.setAdapter(mAdapter);
}

并在onPostExecute

@Override
protected void onPostExecute(Double result) {
    // TODO Auto-generated method stub
    super.onPostExecute(result);
    mAdapter.notifyDataSetChanged();
}

Answer 2

问题是你每次都在重新创建适配器。初始化适配器一次并仅替换onPostExecute

中的数据

List chatHistories;



  // in onPostExecute
adapter.updateData(new_chatHistory);




// in your adapter
updateData(List new_chatHistory){

    chatHistories.addAll(new_chatHistory);

    and adapter.notifyDataSetChanged();
}

Listview会在每2秒后自动向上滚动

2 个答案: