这是我的片段扩展ListFragment的代码，下面是它显示的错误。几乎相同的代码工作正常，除了在活动中我通过列表视图
ListView lv = getListView();
并在片段中通过
lv= (ListView)rootView.findViewById(R.id.list);
它在行java上显示nullpointer异常：109 lv.setOnItemClickListener(new AdapterView.OnItemClickListener()
如果我删除setOnItemClickListener，它会在lv.setAdapter(adapter);上显示空指针异常
SoundCloudFragment.java
public class SoundCloudFragment extends ListFragment {
private ProgressDialog pDialog;
private FragmentActivity myContext;
ListView lv;
@Override
public void onAttach(Activity activity) {
if (activity instanceof FragmentActivity) {
myContext = (FragmentActivity) activity;
}
super.onAttach(activity);
}
// contacts JSONArray
JSONArray contacts = null;
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// mVisulizerView = (VisualizerView)findViewById(R.id.visualizerView);
View rootView = inflater.inflate(R.layout.soundcloud, container, false);
lv= (ListView)rootView.findViewById(R.id.list);
// Get ListView object from xml
// lv = getListView();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id)
{
// getting values from selected ListItem
String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
String cost = ((TextView) view.findViewById(R.id.email)).getText().toString();
String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString();
// Starting single contact activity
Intent in = new Intent(myContext,
SingleContactActivity.class);
in.putExtra("name", TAG_TITLE);
in.putExtra("id", cost);
startActivity(in);
}
});
// Calling async task to get json
new GetContacts().execute();
return rootView;
}
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
pDialog = new ProgressDialog(myContext);
pDialog.setMessage("Please wait...");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);
Log.d("Response: ", "> " + jsonStr);
if (jsonStr != null) {
try {
JSONArray json = new JSONArray(jsonStr);
// looping through All Contacts
for (int i = 0; i < json.length(); i++) {
JSONObject jsonObj = json.getJSONObject(i);
//JSONObject c = contacts.getJSONObject(i);
String title = jsonObj.getString(TAG_TITLE);
String id = jsonObj.getString(TAG_ID);
String kind = jsonObj.getString(TAG_KIND);
String duration =jsonObj.getString(TAG_DURATION);
/* String gender = c.getString(TAG_GENDER);
// Phone node is JSON Object
JSONObject phone = c.getJSONObject(TAG_PHONE);
String mobile = phone.getString(TAG_PHONE_MOBILE);
String home = phone.getString(TAG_PHONE_HOME);
String office = phone.getString(TAG_PHONE_OFFICE);*/
// tmp hashmap for single contact
HashMap<String, String> contact = new HashMap<String, String>();
// adding each child node to HashMap key => value
contact.put(TAG_TITLE, title);
contact.put(TAG_ID, id);
contact.put(TAG_KIND, kind);
contact.put(TAG_DURATION, duration);
// adding contact to contact list
contactList.add(contact);
}
} catch (JSONException e)
{
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (pDialog.isShowing())
pDialog.dismiss();
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
myContext, contactList,
R.layout.soundcloud_item, new String[] { TAG_TITLE, TAG_ID,
TAG_KIND }, new int[] { R.id.name,
R.id.email, R.id.mobile });
lv.setAdapter(adapter);
}
}
}
错误 -
FATAL EXCEPTION: main
java.lang.NullPointerException
at com.peoplecloud.guggu.ui.fragment.SoundCloudFragment.onCreateView(SoundCloudFragment.java:109)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:829)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1035)
at android.app.BackStackRecord.run(BackStackRecord.java:635)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1397)
at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:5086)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：2)
请尝试这种方式，希望这有助于您解决问题。
给出ListView id有两种方法。
1.android预定义ID如：
<强> XML
<ListView
android:id="@android:id/list"
Activty
lv= (ListView) findViewById(android.R.id.list);
片段
lv= (ListView)rootView.findViewById(android.R.id.list);
2.Custom id like：
<强> XML
<ListView
android:id="@+id/list"
Activty
lv= (ListView) findViewById(R.id.list);
片段
lv= (ListView)rootView.findViewById(R.id.list);
答案 1 :(得分：1)
尝试使用此代码获取ListView：
ListView lv = (ListView) getActivity().findViewById(android.R.id.list);
当您使用ListFragment作为基类时。如果您将列表正确放入xml文件中，也可能需要使用android.R.id.list来获取列表。
答案 2 :(得分：0)
试试这个。
ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.soundcloud, container, false);
以及onItemClick
//开始单一联系活动
Intent in = new Intent(getActivity().getApplicationContext(),
SingleContactActivity.class);
in.putExtra("name", TAG_TITLE);
in.putExtra("id", cost);
startActivity(in);