Android自定义Adapter从asynctask添加数据不会被添加

Question

我目前正在尝试将从异步任务接收到的数据添加到自定义适配器。在第一次调用任务时，有一个空列表 "notifications"。在第二次和第三次调用时，收到的通知必须添加到现有通知列表中。

我的问题是新通知不会添加到现有列表中。新通知将替换旧列表。

private class LoadNotificationsTask extends AsyncTask<String, Integer, ArrayList<Notification>> {
    NotificationFragment fragment;
    String parameters;

    private LoadNotificationsTask(NotificationFragment fragment, String parameters) {
        this.fragment = fragment;
        this.parameters = parameters;
    }

    @Override
    protected ArrayList<Notification> doInBackground(String... params) {
        try {
            return Client.getNotifications(this.parameters);
        } catch (Exception e) {
            return new ArrayList<Notification>();
        }
    }

    @Override
    protected void onPostExecute(ArrayList<Notification> notifications) {
        NotificationListAdapter notificationListAdapter = new NotificationListAdapter(notifications);
        setListAdapter(notificationListAdapter);
    }
}


public class NotificationListAdapter extends BaseAdapter {
    private ArrayList<Notification> notifications;

    public NotificationListAdapter(ArrayList<Notification> notifications) {
        super();
        this.notifications = notifications;

    }


    @Override
    public int getCount() {
        return this.notifications.size();
    }

    @Override
    public Object getItem(int position) {
        return this.notifications.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

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

        if (convertView == null) {
            LayoutInflater inflater = LayoutInflater.from(getContext());
            convertView = inflater.inflate(R.layout.notificationlist_item, parent, false);
        }
        final Notification notification = (Notification) this.getItem(position);

        TextView headline = (TextView) convertView.findViewById(R.id.notilist_hostname);
        headline.setText(notification.getNAME1() + "\" +notification.getNAME2());


        return convertView;

    }

Answer 1

首先在 AsyncTask 之外启动 ListView 适配器，即。在 onCreate()

里面

 // Declare class variable
 ArrayList<Notification> mNotifications;
 NotificationListAdapter notificationListAdapter;

 // inside onCreate()
 mNotifications = new ArrayList<Notification>();
 notificationListAdapter = new NotificationListAdapter(mNotifications);
 setListAdapter(notificationListAdapter);

然后使用以下代码编辑您的 AsyncTask postExecute()

@Override
protected void onPostExecute(ArrayList<Notification> notifications) {
    mNotifications.addAll(notifications);
    notificationListAdapter.notifyDataSetChanged();
}

Answer 2

也许更改 getItemId 函数 return 值。

@Override
public long getItemId(int position) {
    return 0;//change return position;
}

Android自定义Adapter从asynctask添加数据不会被添加

Android custom Adapter add data from asynctask will not be added

android

android-arrayadapter

android-asynctask