android - ArrayAdapter无法更新内容

我正在尝试更新ArrayAdapter的内容。我尝试在适配器上调用方法notifyDataSetChanged()，在invalidate()上调用方法ListView，但看不到适配器内的数据被更改。我花了两个小时搜索有关该主题的所有StackOverflow帖子，但是没有一个答案有效。

这是我扩展的ArrayAdapter类

public class ChannelAdapter extends ArrayAdapter<ChannelRow> {

Context context;
int layoutResourceId;
ChannelRow[] data;

public ChannelAdapter(Context context, int layoutResourceId, ChannelRow[] data) {
    super(context, layoutResourceId, data);
    this.layoutResourceId = layoutResourceId;
    this.context = context;
    this.data = data;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;
    ChannelRowHolder holder = null;

    if(row == null)
    {
        LayoutInflater inflater = ((Activity)context).getLayoutInflater();
        row = inflater.inflate(layoutResourceId, parent, false);

        holder = new ChannelRowHolder();
        holder.userName = (TextView)row.findViewById(R.id.userNameTextView);
        holder.channelName = (TextView)row.findViewById(R.id.channelNameTextView);

        row.setTag(holder);
    }
    else
    {
        holder = (ChannelRowHolder)row.getTag();
    }

    ChannelRow channelRow = data[position];
    holder.userName.setText(channelRow.getUserName());
    holder.channelName.setText(channelRow.getChannelName());

    return row;
}

static class ChannelRowHolder
{
    TextView userName;
    TextView channelName;
}

}

以下是我处理适配器的Activity。

public class ChannelNameActivity extends Activity {

private ListView channelListView ;
private ChannelRow[] channelData;
private ChannelAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    ...

    this.setContentView(R.layout.activity_channelname);

    // create ListView of channels
    grabSessions();
    channelData = new ChannelRow[]{ // default data
        new ChannelRow("user1", "channel1"),
        new ChannelRow("user2", "channel2")
    };

    // attach ListView adapters/views
    adapter = new ChannelAdapter(this, R.layout.channel_row, channelData);
    channelListView = (ListView) findViewById(R.id.channelListView);
    final View contentView = (View)getLayoutInflater().inflate(R.layout.activity_channelname, null);
    channelListView.addHeaderView(contentView);
    channelListView.setAdapter(adapter);

....
}

private void grabSessions() {
    ParseQuery<ParseObject> query = ParseQuery.getQuery("Session");
    query.findInBackground(new FindCallback<ParseObject>() {
        public void done(List<ParseObject> objects, ParseException e) {
            if (e == null) {
                createSessionsList((ArrayList<ParseObject>) objects);
            } else {
                // error with query
            }
        }
    });
}

/**
 * Called from grabSessions()
 * Initializes channelData with the queried ParseObject Sessions
 * @param objects the queried Sessions
 */
private void createSessionsList(ArrayList<ParseObject> objects){
    ArrayList<ChannelRow> channels = new ArrayList<>();
    ChannelRow newRow = null;

    for (ParseObject o : objects){
        newRow = new ChannelRow((String)o.get("hostName"), (String)o.get("chatTitle"));
        channels.add(newRow);
    }

    channelData = channels.toArray(new ChannelRow[channels.size()]);
    adapter.notifyDataSetChanged();
    channelListView.invalidate();
}

}

最佳答案

先生;

检查这个private ChannelRow[] channelData;这是您的实例变量，您可以通过onCreate()实例化它

channelData = new ChannelRow[]{ // default data
    new ChannelRow("user1", "channel1"),
    new ChannelRow("user2", "channel2")
}; // channelData is holding is reference to the object being created with the `new` keyword

因此，例如，如果您向channelData添加另一个对象并调用notifyDataSetChanged()，它将刷新，但是在createSessionsList(ArrayList<ParseObject> objects)方法中，您将channelData分配给了一个新对象，例如channelData = channels.toArray(new ChannelRow[channels.size()]);，而该引用不是ListView的Adapter数据指向，因此您的notifyDataSetChanged()无法工作，因为它没有更改。您要做的是回顾实例化行，这是完整的代码

private void createSessionsList(ArrayList<ParseObject> objects){
ArrayList<ChannelRow> channels = new ArrayList<>();
ChannelRow newRow = null;

for (ParseObject o : objects){
    newRow = new ChannelRow((String)o.get("hostName"), (String)o.get("chatTitle"));
    channels.add(newRow);
}

channelData = channels.toArray(new ChannelRow[channels.size()]);
adapter = new ChannelAdapter(this, R.layout.channel_row, channelData);
//edit started here
// set your Listview to the adapter
channelListView.setAdapter(adapter); // you set your list to the new adapter
adapter.notifyDataSetChanged();// you can remove it if you like
}

编辑1

如果您不喜欢一直使用此行adapter = new ChannelAdapter(this, R.layout.channel_row, channelData);的想法，我建议您使用ArrayList并使用ArrayList.add(Object o)函数更新您的项目，那么您可以全部notifyDataSetChanged() ..

希望能帮助到你..

关于android - ArrayAdapter无法更新内容，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28788421/