使用自定义适配器将数据从XML解析为列表

Question

I am getting data from an XML uploaded on a website. I want to display the text from the XML in a custom ListView , which has two TextView s. The 'title' should go into the upper TextView and the 'guid' into the lower TextView . I'm not sure how I should go about doing this. I've written the following Custom Adapter.

CustomAdapter.java

public class CustomAdapter extends BaseAdapter {

    private ArrayList list;
    private LayoutInflater layoutInflater;

    public CustomAdapter(Context context, ArrayList list) {
        this.list= list;
        layoutInflater = LayoutInflater.from(context);
    }

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

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

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

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

        final ViewHolder holder;
        if (convertView == null) {

            convertView = layoutInflater.inflate(R.layout.layout_list_row, null);

            holder = new ViewHolder();
            holder.backgroundImage = (ImageView) convertView.findViewById(R.id.backgroundImage);
            holder.topText = (TextView) convertView.findViewById(R.id.topText);
            holder.bottomText = (TextView) convertView.findViewById(R.id.bottomText);
            convertView.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        DiscourseItem discourseItem = (DiscourseItem) discourseList.get(position);
        holder.topText.setText(discourseItem.getTopText());
        holder.bottomText.setText(discourseItem.getBottomText());

        return convertView;
    }

    static class ViewHolder {
        ImageView backgroundImage;
        TextView topText;  //This should display the text in the 'title' field
        TextView bottomText; //This should display the text in the 'guid' field
    }

}

I'm currently able to display the two separately in separate ListView s with normal ArrayAdapter s. Here's the code I've written.

XMLParser.java

public class XMLParser extends AsyncTask {

    private URL url;
    public ArrayList<String> title = new ArrayList<>();
    public ArrayList<String> guid = new ArrayList<>();

    @Override
    protected Object doInBackground(Object[] objects) {
        try {
            url = new URL(removed);

            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            factory.setNamespaceAware(false);
            XmlPullParser xpp = factory.newPullParser();

            xpp.setInput(getInputStream(url), null);

            boolean insideItem = false;

            int eventType = xpp.getEventType();
            while (eventType != XmlPullParser.END_DOCUMENT) {
                if (eventType == XmlPullParser.START_TAG) {
                    if (xpp.getName().equalsIgnoreCase("item")){
                        insideItem = true;
                    } else if (xpp.getName().equalsIgnoreCase("title")){
                        if (insideItem)
                            title.add(xpp.nextText());
                    } else if (xpp.getName().equalsIgnoreCase("guid")){
                        if (insideItem)
                            guid.add(xpp.nextText());
                    }
                } else if (eventType == XmlPullParser.END_TAG && xpp.getName().equalsIgnoreCase("item")){
                    insideItem = false;
                }
                eventType = xpp.next();
            }
        } catch (MalformedURLException e){
            e.printStackTrace();
        } catch (XmlPullParserException e){
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return title;
    }

    public InputStream getInputStream(URL url){
        try {
            return url.openConnection().getInputStream();
        } catch (IOException e){
            e.printStackTrace();
        }
        return null;
    }

    public ArrayList<String> titles(){
        return title;
    }

    public ArrayList<String> guids(){
        return guid;
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        parser = new XMLParser();
        parser.execute();
        title = parser.titles();
        guid = parser.guids();

        final Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
           @Override
            public void run() {
                discourseList = getDiscourseList();
            }
            }, 2000);
        }
        });

        ListView listView = (ListView) findViewById(R.id.discourseList);
        listView.setAdapter(new CustomAdapter(this, discourseList));
    }

    private ArrayList<DiscourseItem> getDiscourseList() {
        ArrayList<DiscourseItem> listData = new ArrayList<DiscourseItem>();
        String[] topText = new String[title.size()];
        topText = title.toArray(topText);

        String[] bottomText = new String[guid.size()];
        bottomText = guid.toArray(bottomText);

        for (int i = 0; i <= title.size(); i++) {
            try {
                DiscourseItem discourseItem = new DiscourseItem();
                discourseItem.setTopText(topText[i]);
                discourseItem.setBottomText(bottomText[i]);
                listData.add(discourseItem);
            } catch (ArrayIndexOutOfBoundsException e){
                e.printStackTrace();
            }
        }
        return listData;
    }
}

Edit :

I've made the above changes. Now when the parser runs and calls getDiscourseList() , it throws the following error at discourseItem.setTopText(topText[i]); :

java.lang.ArrayIndexOutOfBoundsException: length=2; index=2

Answer 1

You can create wrapper class for your upper and bottom values ( something like this, consider another name as I don't know the context of your data):

public class TitleGuidPair {
  private final String title;
  private final String guid;
  public TitleGuidPair(String title, String guid) {
    this.title = title;
    this.guid = guid;
  }
 //getters
}

And then parse your result to ArrayList of TitleGuidPair. If you want to keep your parsing algorithm you can make some post-processing and build your TitleGuidPairs afterwards from the two lists that you have.

Having that step behind just pass to your adapter List of TitleGuidPairs and in the getView method set top and bottom text like

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

    final ViewHolder holder;
    if (convertView == null) {

        convertView = layoutInflater.inflate(R.layout.layout_list_row, null);

        holder = new ViewHolder();
        holder.backgroundImage = (ImageView) convertView.findViewById(R.id.backgroundImage);
        holder.topText = (TextView) convertView.findViewById(R.id.topText);
        holder.bottomText = (TextView)    convertView.findViewById(R.id.bottomText);
        TitleGuidPair titleGuidPair = list.get(position);  
        holder.topText.setText(titleGuidPair.getTitle());
        holder.bottomText.setText(titleGuidPair.getGuid());
        convertView.setTag(holder);

    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    return convertView;
}