I am building an app that uses ListView and a custom adapter extending BaseAdapter to handle the data to the ListView. The code is as follows:
newlist.java compiles/runs fine
public class newslist extends Activity {
public static final String tag = "newslist";
ListView listNews;
MyListAdapter listAdapter;
/** Set or Grab the URL */
public static final String parseURL = "http://www.example.com.gr/article.php";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.newslist);
/** Array Lists */
ArrayList<String> titles = new ArrayList<String>();
ArrayList<String> links = new ArrayList<String>();
ArrayList<String> dates = new ArrayList<String>();
Log.d(newslist.tag, "****** parseURL = " + parseURL);
listNews = (ListView) findViewById(R.id.listNews);
try {
/** Open URL with Jsoup */
Document doc = Jsoup.connect(parseURL).get();
/** Grab classes we want */
Elements pcontent = doc.getElementsByClass("content_title");
Elements pdates = doc.getElementsByClass("content_datecreated_left");
/** Loop for grabbing TITLES within parent element */
for (Element ptitles : pcontent) {
/** Grab Anchors */
Elements ptitle = ptitles.getElementsByTag("a");
for (Element title : ptitle) {
titles.add(title.text());
}
}
/** Loop for grabbing LINKS within parent element */
for (Element plinks : pcontent) {
/** Grab anchors */
Elements plink = plinks.getElementsByTag("a");
for (Element link : plink) {
links.add(link.attr("abs:href")); /** parse absolute address */
}
}
/** Loop for grabbing DATES within parent element */
for (Element pdate : pdates) {
dates.add(pdate.text()) ;
}
//TODO: Regex on Date
//String content: Main Activity Content
int i=0;
int num = titles.size();
String[] printDates = new String[num];
for (i=0; i < num; i++)
{
//substring(25) leaves a space after the date, eg "26/6/2011 "
//content[i] = titles.get(i) + "\n Date: " + dates.get(i).substring(25);
printDates[i] = dates.get(i).substring(25);
}
/** Create an ArrayAdapter, that will actually make the Strings above
* appear in the ListView */
listAdapter = new MyListAdapter(this, titles, dates);
listNews.setAdapter(listAdapter);
} catch (Exception e) {
Log.e(newslist.tag, "****** Failed to Parse URL:" + e.getMessage());
e.printStackTrace();
}
} /*- OnCreate End -*/
} /*- Class End -*/
MyListAdapter.java runs a NPE at line 75:
public class MyListAdapter extends BaseAdapter {
public final static String tag = "MyListAdapter";
public Context context;
public ArrayList<String> title;
public ArrayList<String> date;
public LayoutInflater inflater;
public MyListAdapter(Activity context, ArrayList<String> title, ArrayList<String> date) {
super();
this.context = context;
this.title = title;
this.date = date;
this.inflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
// Auto-generated method stub
return this.title.size();
}
public Object getItem(int position) {
//Auto-generated method stub
return this.title.get(position);
}
public long getItemId(int position) {
// Auto-generated method stub
return position;
}
private static class ViewHolder {
TextView titleView;
TextView dateView;
}
public View getView(int position, View convertView, ViewGroup parent)
{
// Auto-generated method stub
ViewHolder holder;
Log.d(tag, "****** convertView: " + convertView);
if (convertView == null)
{
convertView = inflater.inflate(R.layout.listrow, null);
holder = new ViewHolder();
holder.titleView = (TextView) convertView.findViewById(R.id.listTitle);
holder.dateView = (TextView) convertView.findViewById(R.id.listDate);
convertView.setTag(holder);
}
else
{
holder = (ViewHolder) convertView.getTag();
}
Log.d(tag, "****** Title: " + title.get(position));
Log.d(tag, "****** findViewById: " + convertView.findViewById(R.id.listTitle));
Log.d(tag, "****** holder.titleView: " + holder.titleView);
holder.titleView.setText(title.get(position));
holder.dateView.setText(date.get(position));
//notifyDataSetChanged();
return convertView;
}
}
Line 75 is:
holder.titleView.setText(title.get(position));
However I have tracked the problem to line 62:
holder.titleView = (TextView) convertView.findViewById(R.id.listTitle);
where it seems from my debugging messages that holder.titleView is null
I have tried cleaning/erasing bin folder and rebuilding the project to no avail. I think the problem lies in the View R.id.listTitle not being found. But i have no idea why.
I will also include my two xml files for previewing
newslist.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/title"
android:gravity="center|top"
android:textSize="20dip"
android:textStyle="bold"
android:text="@string/titleNewslist"
/>
<ListView
android:id="@+id/listNews"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
</ListView>
</LinearLayout>
listrow.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:name="@+id/listTitle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="top|left"
android:textSize="18dip"
android:textStyle="bold"
android:text="TextView">
</TextView>
<TextView
android:name="@+id/listDate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="bottom|right"
android:textSize="12dip"
android:textStyle="bold"
android:textColor="@android:color/white"
android:text="TextView">
</TextView>
</LinearLayout>
You never assign anything to titleView.
You need to do the following in your onCreate() after super.onCreate()
titleView = (TextView) this.getViewById(R.id.listTitle);
Make sure to declare titleView as a field at the top of your class so the rest of your class can access it, if you need to.
Hope this helps!
EDIT:
An important note I just noticed:
android:name="@+id/myName"
is NOT the same as
android:id="@+id/myName"
You need to make sure you declare the ids, or you will not be able to access the layout elements.