我从androidhive找到了这个自定义列表视图教程，我试图实现onclick，意图显示自定义列表视图中的值。每当我点击这些项目时，应用程序就崩溃了。请帮忙！
CustomListView.Java
public class CustomizedListView extends Activity {
// All static variables
static final String URL = "http://myurl/Announcement.xml";
// XML node keys
static final String KEY_ANNOUNCEMENT = "announcement"; // parent node
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_INFORMATION = "information";
static final String KEY_DATE = "date";
static final String KEY_ICON = "icon";
ListView list;
LazyAdapter adapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ANNOUNCEMENT);
// looping through all song nodes <song>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_INFORMATION, parser.getValue(e, KEY_INFORMATION));
map.put(KEY_DATE, parser.getValue(e, KEY_DATE));
map.put(KEY_ICON, parser.getValue(e, KEY_ICON));
// adding HashList to ArrayList
songsList.add(map);
}
list=(ListView)findViewById(R.id.list);
// Getting adapter by passing xml data ArrayList
adapter=new LazyAdapter(this, songsList);
list.setAdapter(adapter);
// Click event for single list row
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String title = ((TextView) view.findViewById(R.id.title)).getText().toString();
String information = ((TextView) view.findViewById(R.id.information)).getText().toString();
String date = ((TextView) view.findViewById(R.id.date)).getText().toString();
String tag = view.getTag().toString();
// Starting new intent
Intent intent = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
intent.putExtra("title",KEY_TITLE);
intent.putExtra("information",KEY_INFORMATION);
intent.putExtra("date",KEY_DATE);
startActivity(intent);
}
});
}
LazyAdapter.Java
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.list_row, null);
TextView title = (TextView)vi.findViewById(R.id.title); // title
TextView date = (TextView)vi.findViewById(R.id.duration); // duration
ImageView icon =(ImageView)vi.findViewById(R.id.list_image); // thumb image
HashMap<String, String> song = new HashMap<String, String>();
song = data.get(position);
vi.setTag(song.get(CustomizedListView.KEY_ID));
// Setting all values in listview
title.setText(song.get(CustomizedListView.KEY_TITLE));
date.setText(song.get(CustomizedListView.KEY_DATE));
imageLoader.DisplayImage(song.get(CustomizedListView.KEY_ICON), icon);
return vi;
}
}
SingleMenuItemActivity.Java
public class SingleMenuItemActivity extends Activity {
// XML node keys
static final String KEY_TITLE = "title";
static final String KEY_INFORMATION = "information";
static final String KEY_DATE = "date";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_single_menu_item);
// getting intent data
Intent in = getIntent();
// Get XML values from previous intent
String title = getIntent().getExtras().getString("title");
String information = getIntent().getExtras().getString("information");
String date = getIntent().getExtras().getString("date");
// Displaying all values on the screen
TextView lblName = (TextView) findViewById(R.id.title);
TextView lblCost = (TextView) findViewById(R.id.information);
TextView lblDesc = (TextView) findViewById(R.id.date);
lblName.setText(title);
lblCost.setText(information);
lblDesc.setText(date);
}
}
logcat的
12-07 20:01:36.575: W/dalvikvm(1167): threadid=1: thread exiting with uncaught exception (group=0x4188f898)
12-07 20:01:36.575: E/AndroidRuntime(1167): FATAL EXCEPTION: main
12-07 20:01:36.575: E/AndroidRuntime(1167): java.lang.NullPointerException
12-07 20:01:36.575: E/AndroidRuntime(1167): at com.example.androidhive.CustomizedListView$1.onItemClick(CustomizedListView.java:79)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.widget.AdapterView.performItemClick(AdapterView.java:301)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.widget.AbsListView.performItemClick(AbsListView.java:1510)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.widget.AbsListView$PerformClick.run(AbsListView.java:3333)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.os.Handler.handleCallback(Handler.java:730)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.os.Handler.dispatchMessage(Handler.java:92)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.os.Looper.loop(Looper.java:137)
12-07 20:01:36.575: E/AndroidRuntime(1167): at android.app.ActivityThread.main(ActivityThread.java:5419)
12-07 20:01:36.575: E/AndroidRuntime(1167): at java.lang.reflect.Method.invokeNative(Native Method)
12-07 20:01:36.575: E/AndroidRuntime(1167): at java.lang.reflect.Method.invoke(Method.java:525)
12-07 20:01:36.575: E/AndroidRuntime(1167): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
12-07 20:01:36.575: E/AndroidRuntime(1167): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
12-07 20:01:36.575: E/AndroidRuntime(1167): at dalvik.system.NativeStart.main(Native Method)