Question

我正在尝试使用自定义适配器为Fragment创建一个填充了消息的列表视图。我的android项目运行没有问题或错误。我可以看到消息正确地传递给构造函数。我认为我的getView不会被调用，我相信它会自动发生。我把打印件放在适配器的getView中，但它们永远不会消失。

这是我的MessageAdapter

public class MessageAdapter extends ArrayAdapter<message>  {

private final Context context;
private final int layoutResourceId;
private final ArrayList<message> messages;


public MessageAdapter(Context context, int layoutResourceId, ArrayList<message> messages) {
    super(context, layoutResourceId);
    this.context = context;
    this.layoutResourceId = layoutResourceId;
    this.messages = messages;
}

@Override
public View getView(int i, View convertView, ViewGroup viewGroup) {
    View row = convertView;
    ViewHolder  holder = null;
    int direction = messages.get(i).userType;
    //show message on left or right, depending on if
    //it's incoming or outgoing
    System.out.println("try this");
    if (row == null) {
        LayoutInflater inflater = ((Activity)context).getLayoutInflater(); 

        int res = 0;
        if (direction == 0) {
            res = R.layout.message_right;
        } else if (direction == 1) {
            res = R.layout.message_left;
        }

        row = inflater.inflate(res, viewGroup, false);
        holder = new ViewHolder();

        holder.txtMessage = (TextView) row.findViewById(R.id.txtMessage);
        holder.txtDate = (TextView) row.findViewById(R.id.txtDate);
        row.setTag(holder);
    }

     System.out.println(messages.get(i).message);
     holder.txtMessage.setText(messages.get(i).message);
     holder.txtDate.setText(messages.get(i).time);

     return row;
}

static class ViewHolder {
    TextView txtMessage;
    TextView txtDate;
}

}

这就是我在片段中调用适配器的地方。

 public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        
    View messagesView = inflater.inflate(R.layout.messages, container, false);
    ListView listView = (ListView)messagesView.findViewById(R.id.listMessages);

    ArrayList<message> messages = getMessages();

    MessageAdapter adapter = new MessageAdapter(getActivity(), R.id.listMessages, messages);
    listView.setAdapter(adapter);
    ...

编辑：按要求获取消息。

    String[] messageArray = getMessages(); // get messages returns an array of json encoded rows from the db

    for(int i=0; i<messageArray.length; i++) {
        String theMess = null, time = null;
        int userType = 0;

        JSONObject jsonObject = null;
        try {
            jsonObject = new JSONObject(messageArray[i]);
        } catch (JSONException e) {
            e.printStackTrace();
        }
        try {theMess = jsonObject.getString("message");} catch (JSONException e) {}
        try {time = jsonObject.getString("time");} catch (JSONException e) {}
        try {userType = jsonObject.getInt("userType");} catch (JSONException e) {}

        message newMessage = new message(theMess, time, userType);
        messages.add(newMessage);   
    }

Answer 1

您缺少getSize方法。添加getsize和getItem方法后，这将按预期工作

Answer 2

此外，您还必须在getview（）方法中向viewgroup添加视图。

Answer 3

更改

super(context, layoutResourceId);

到

super(context, layoutResourceId, messages);

您不需要getCount()或getItem()。除非你需要自己的特殊逻辑，否则ArrayAdapter已经有了适用它们的实现。

Answer 4

您不需要ArrayList<message> messages，ArrayAdapter已经维护了自己ArrayList。您应该将消息传递给超级ctr，并使用getItem(position)方法中的getView。

在android中使用自定义适配器填充listView

4 个答案: