java - 自定义适配器未在 ListView 上显示任何数据

Question

我的 listView 需要一个自定义适配器。它需要传递给 ASyncTask，后者将从 RSS 提要中获取一些数据，然后希望将该数据(目前是标题和日期，均为字符串)设置到该行。

我想出的代码如下，但它没有对适配器做任何事情。

主 Activity .java

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;


public class MainActivity extends Activity
{
    private ListView listOne;
    private ListView listTwo;
    RssListViewAdapter adapterOne;
    RssListViewAdapter adapterTwo;

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.rss_layout);

        //Connect all three columns to their ListViews
        listOne = (ListView) findViewById(R.id.listOne);
        listTwo = (ListView) findViewById(R.id.listTwo);

        //Create both adapaters
        //TODO: Make custom adapater
        adapterOne = new RssListViewAdapter(this);
        adapterTwo = new RssListViewAdapter(this);


        //Class once for each column. Pass feed URL and Adapter.
        new GetRssFeed("http://feeds.arstechnica.com/arstechnica/index", adapterOne, listOne).execute();
        new GetRssFeed("http://feeds.skynews.com/feeds/rss/home.xml", adapterTwo, listTwo).execute();

    }



}

GetRssFeed.java

import android.os.AsyncTask;
import android.util.Log;
import android.widget.ListView;

/**
 * Created by jameskrawczyk on 07/04/16.
 */
public class GetRssFeed extends AsyncTask<String, Void, Void>
{

    String url;
    RssListViewAdapter adapter;
    ListView listToUse;

    public GetRssFeed(String urlInput, RssListViewAdapter adapterInput, ListView listInput)
    {
        this.url = urlInput;
        this.adapter = adapterInput;
        this.listToUse = listInput;
    }

    @Override
    protected Void doInBackground(String... params)
    {
        try
        {
            RssReader rssReader = new RssReader(url);
            Integer i = 0;

            adapterItem adaptItem = new adapterItem();

            for (RssItem item : rssReader.getItems())
            {
                adaptItem.setHeader(item.getTitle());
                adaptItem.setDate(item.getDate());
                adapter.add(adaptItem);
                i++;
                if(i == 7)
                {
                    break;
                }
            }

        } catch (Exception e)
        {
            Log.v("Error Parsing Data", e + "");
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid)
    {
        super.onPostExecute(aVoid);
        listToUse.setAdapter(adapter);
        adapter.notifyDataSetChanged();

    }
}

RssItem

public class RssItem {
    String title;
    String description;
    String link;
    String imageUrl;
    String pubDate;

    public String getDescription() {
        return description;
    }

    public String getImageUrl() {
        return imageUrl;
    }

    public void setImageUrl(String imageUrl) {
        this.imageUrl = imageUrl;
    }

    public String getTitle() {
        return title;
    }

    public String getLink() {
        return link;
    }

    public String getDate(){return pubDate;}

    public void setLink(String link) {this.link = link;}

    public void setDescription(String description) {
        this.description = description;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setDate(String pubDate) {this.pubDate = pubDate;}
}

RssListViewAdapater

import java.util.ArrayList;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

public class RssListViewAdapter extends ArrayAdapter<adapterItem> {

    private final Context context;
    private adapterItem itemsArrayList;

    public RssListViewAdapter(Context context) {

        super(context, R.layout.basic_list_item);
        this.context = context;

    }

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


        LayoutInflater inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);


        View rowView = inflater.inflate(R.layout.basic_list_item, parent, false);


        TextView headerView = (TextView) rowView.findViewById(R.id.headerName);
        TextView dateView = (TextView) rowView.findViewById(R.id.dateTime);

        headerView.setText(itemsArrayList.getHeader());
        dateView.setText(itemsArrayList.getDate());


        return rowView;
    }

    @Override
    public void add(adapterItem theData)
    {
        this.itemsArrayList = theData;
    }
}

适配器项

public class adapterItem {

    private String header;
    private String date;

    public adapterItem() {
        super();
        this.header = header;
        this.date = date;
    }


    public void setHeader(String head)
    {
        header = head;
    }

    public void setDate(String dat)
    {
        date = dat;
    }

    public String getHeader()
    {
        return header;
    }

    public String getDate()
    {
        return date;
    }
}

Answer 1

在 GetRssFeed 的 doInBackground 中，您在 for 循环之外实例化一个 adapterItem，这只会导致最后一个 RssItem 被添加到适配器。我认为您应该在 for 循环中实例化每个 adapterItem。

for (RssItem item : rssReader.getItems())
{
    adapterItem adaptItem = new adapterItem();
    adaptItem.setHeader(item.getTitle());
    adaptItem.setDate(item.getDate());
    adapter.add(adaptItem);
    i++;
    if(i == 7)
    {
       break;
    }
}

与此同时，您似乎没有正确覆盖 RssListViewAdapater 的 add 方法。事实上，您根本不必覆盖 add。 ArrayAdapter 将为您处理。