Question

我的listView需要一个自定义适配器。它需要传递给ASyncTask，它将从RSS提要中获取一些数据，然后希望将该数据（当前标题和日期，两个字符串）设置为该行。

我提出的代码如下，但它没有对适配器做任何事情。

MainActivity.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();

    }
}

的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;
    }
}

adapterItem

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doInBackground的{{1}}中，您实例化GetRssFeed外部adapterItem循环，这会导致只有最后一个for被添加到适配器。我认为你应该在RssItem循环中实例化每个adapterItem。

for

与此同时，您似乎无法正确覆盖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; } } add方法。事实上，您根本不必覆盖RssListViewAdapater。 add将为您处理。

Answer 2

尝试这个。

替换

adapter.add(adaptItem);

代码为

adapter.addDatas(adaptItem);

在 GetRssFeed.java 中

并将 RssListViewAdapter.java 适配器类替换为

public class RssListViewAdapter extends BaseAdapter {

private final Context context;
private ArrayList<adapterItem> itemsArrayList;


public RssListViewAdapter(Context context) {

    this.context = context;
    itemsArrayList=new ArrayList<adapterItem>();

}

public void addDatas(adapterItem item){
    itemsArrayList.add(item);
}
@Override
public long getItemId(int position) {
    return position;
}

@Override
public Object getItem(int position) {
    return getItem(position);
}

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




@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.get(position).getHeader());
    dateView.setText(itemsArrayList.get(position).getDate());
    return rowView;
}


}

由Defalut RssReader 没有从xml读取pubDate。如果您希望在 RSSReader 中阅读pubDate，请复制代码并将其替换为 RssHandler.java

<强> RssHandler.Java

public class RssHandler extends DefaultHandler {
private List<RssItem> rssItemList;
private RssItem currentItem;
private boolean parsingTitle;
private boolean parsingLink;
private boolean parsingDescription;
private boolean parsingPubDate;
public RssHandler() {
    //Initializes a new ArrayList that will hold all the generated RSS items.
    rssItemList = new ArrayList<RssItem>();
}

public List<RssItem> getRssItemList() {
    return rssItemList;
}


//Called when an opening tag is reached, such as <item> or <title>
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
    if (qName.equals("item"))
        currentItem = new RssItem();
    else if (qName.equals("title"))
        parsingTitle = true;
    else if (qName.equals("link"))
        parsingLink = true;
    else if (qName.equals("description"))
        parsingDescription = true;
    else if(qName.equals("pubDate"))
        parsingPubDate=true;
    else if (qName.equals("media:thumbnail") || qName.equals("media:content") || qName.equals("image")) {
        if (attributes.getValue("url") != null)
            currentItem.setImageUrl(attributes.getValue("url"));

    }
}

//Called when a closing tag is reached, such as </item> or </title>
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
    if (qName.equals("item")) {
        //End of an item so add the currentItem to the list of items.
        rssItemList.add(currentItem);
        currentItem = null;
    } else if (qName.equals("title"))
        parsingTitle = false;
    else if (qName.equals("link"))
        parsingLink = false;
    else if (qName.equals("description"))
        parsingDescription = false;
    else if(qName.equals("pubDate"))
        parsingPubDate=false;
}

//Goes through character by character when parsing whats inside of a tag.
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
    if (currentItem != null) {
        //If parsingTitle is true, then that means we are inside a <title> tag so the text is the title of an item.
        if (parsingTitle)
            currentItem.setTitle(new String(ch, start, length));
            //If parsingLink is true, then that means we are inside a <link> tag so the text is the link of an item.
        else if (parsingLink)
            currentItem.setLink(new String(ch, start, length));
            //If parsingDescription is true, then that means we are inside a <description> tag so the text is the description of an item.
        else if (parsingDescription)
            currentItem.setDescription(new String(ch, start, length));
        else if(parsingPubDate)
            currentItem.setDate(new String(ch,start,length));
    }
}
}

Answer 3

有同样的问题。在android 4.1中，一切都在行中可见。但在android 6中是空行。我搞砸了。但找到原因。

只需添加文字颜色

android:textColor="#000"

自定义适配器未在ListView上显示任何数据

3 个答案: