在应用程序崩溃的情况下，我无法调用notifyDataSetChanged。
ListFragment类：
public class ServerListFragment extends ListFragment implements OnTaskCompleteListener {
private AsyncTaskManager mAsyncTaskManager;
private ServersDataSource datasource;
private ArrayList<Server> servers;
private boolean paused = false;
private boolean generateList = true;
private String operation = "";
/**
* The serialization (saved instance state) Bundle key representing the
* activated item position. Only used on tablets.
*/
private static final String STATE_ACTIVATED_POSITION = "activated_position";
/**
* The fragment's current callback object, which is notified of list item
* clicks.
*/
private Callbacks mCallbacks = sDummyCallbacks;
/**
* The current activated item position. Only used on tablets.
*/
private int mActivatedPosition = ListView.INVALID_POSITION;
/**
* A callback interface that all activities containing this fragment must
* implement. This mechanism allows activities to be notified of item
* selections.
*/
public interface Callbacks {
/**
* Callback for when an item has been selected.
*/
public void onItemSelected(String id);
}
/**
* A dummy implementation of the {@link Callbacks} interface that does
* nothing. Used only when this fragment is not attached to an activity.
*/
private static Callbacks sDummyCallbacks = new Callbacks() {
@Override
public void onItemSelected(String id) {
}
};
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public ServerListFragment() {
}
/*
* Default list adapter
*/
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// retainInstance and survive on configuration changes (rotation)
setRetainInstance(true);
// Create manager and set this activity as context and listener
mAsyncTaskManager = new AsyncTaskManager(getActivity(), this);
// Handle task that can be retained before
mAsyncTaskManager.handleRetainedTask(getActivity().getLastNonConfigurationInstance());
// start async task
getServersServices();
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// Restore the previously serialized activated item position.
if (savedInstanceState != null
&& savedInstanceState.containsKey(STATE_ACTIVATED_POSITION)) {
setActivatedPosition(savedInstanceState
.getInt(STATE_ACTIVATED_POSITION));
}
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// Activities containing this fragment must implement its callbacks.
if (!(activity instanceof Callbacks)) {
throw new IllegalStateException(
"Activity must implement fragment's callbacks.");
}
mCallbacks = (Callbacks) activity;
}
@Override
public void onDetach() {
super.onDetach();
// Reset the active callbacks interface to the dummy implementation.
mCallbacks = sDummyCallbacks;
}
@Override
public void onListItemClick(ListView listView, View view, int position,
long id) {
super.onListItemClick(listView, view, position, id);
// Notify the active callbacks interface (the activity, if the
// fragment is attached to one) that an item has been selected.
mCallbacks.onItemSelected(DummyContent.ITEMS.get(position).id);
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if (mActivatedPosition != ListView.INVALID_POSITION) {
// Serialize and persist the activated item position.
outState.putInt(STATE_ACTIVATED_POSITION, mActivatedPosition);
}
}
/**
* Turns on activate-on-click mode. When this mode is on, list items will be
* given the 'activated' state when touched.
*/
public void setActivateOnItemClick(boolean activateOnItemClick) {
// When setting CHOICE_MODE_SINGLE, ListView will automatically
// give items the 'activated' state when touched.
getListView().setChoiceMode(
activateOnItemClick ? ListView.CHOICE_MODE_SINGLE
: ListView.CHOICE_MODE_NONE);
}
private void setActivatedPosition(int position) {
if (position == ListView.INVALID_POSITION) {
getListView().setItemChecked(mActivatedPosition, false);
} else {
getListView().setItemChecked(position, true);
}
mActivatedPosition = position;
}
public void notifyDataSetChanged() {
((BaseAdapter) getListAdapter()).notifyDataSetChanged();
}
public void getServersServices() {
datasource = new ServersDataSource(getActivity());
datasource.open();
datasource.emptyServersTable();
operation = "GetSevers";
mAsyncTaskManager.setupTask(new Task(getResources(), getActivity(), getResources().getString(R.string.refreshing), operation, 0, ""));
}
public void onTaskComplete(Task task) {
if (task.isCancelled()) {
// Report about cancel
if (DEBUG) Log.i(TAG, "ServersStatus onTaskComplete task cancel");
} else {
// Get result
Boolean result = null;
try {
result = task.get();
} catch (Exception e) {
if (DEBUG) Log.e(TAG, "ServersStatus onTaskComplete error: " + e.toString());
}
// Report about result
servers = datasource.getAllServers();
if(servers.size() > 0 && generateList){
DummyContent.setContext(servers);
notifyDataSetChanged();
}
operation = "";
}
generateList = true;
}
// Our handler for received Intents. This will be called whenever an Intent
// with an action named "custom-event-name" is broadcasted.
private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
// Get extra data included in the Intent
String message = intent.getStringExtra("message");
if (message.equals("Refresh list")) {
servers = datasource.getAllServers();
getServersServices();
}
}
};
}
错误日志：
> 09-30 15:15:39.360: E/AndroidRuntime(14322): FATAL EXCEPTION: main
> 09-30 15:15:39.360: E/AndroidRuntime(14322):
> java.lang.NullPointerException 09-30 15:15:39.360:
> E/AndroidRuntime(14322): at
> com.ww.www.ServerListFragment.notifyDataSetChanged(ServerListFragment.java:307)
> 09-30 15:15:39.360: E/AndroidRuntime(14322): at
> com.ww.www.ServerListFragment.onTaskComplete(ServerListFragment.java:385)
> 09-30 15:15:39.360: E/AndroidRuntime(14322): at
> com.ww.www.core.AsyncTaskManager.onComplete(AsyncTaskManager.java:67)
> 09-30 15:15:39.360: E/AndroidRuntime(14322): at
> com.ww.www.core.Task.onPostExecute(Task.java:330) 09-30 15:15:39.360:
> E/AndroidRuntime(14322): at
> com.ww.www.core.Task.onPostExecute(Task.java:1) 09-30 15:15:39.360:
> E/AndroidRuntime(14322): at
> android.os.AsyncTask.finish(AsyncTask.java:631) 09-30 15:15:39.360:
> E/AndroidRuntime(14322): at
> android.os.AsyncTask.access$600(AsyncTask.java:177) 09-30
> 15:15:39.360: E/AndroidRuntime(14322): at
> android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
> 09-30 15:15:39.360: E/AndroidRuntime(14322): at
> android.os.Handler.dispatchMessage(Handler.java:99) 09-30
> 15:15:39.360: E/AndroidRuntime(14322): at
> android.os.Looper.loop(Looper.java:137) 09-30 15:15:39.360:
> E/AndroidRuntime(14322): at
> android.app.ActivityThread.main(ActivityThread.java:4898) 09-30
> 15:15:39.360: E/AndroidRuntime(14322): at
> java.lang.reflect.Method.invokeNative(Native Method) 09-30
> 15:15:39.360: E/AndroidRuntime(14322): at
> java.lang.reflect.Method.invoke(Method.java:511) 09-30 15:15:39.360:
> E/AndroidRuntime(14322): at
> com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1008)
> 09-30 15:15:39.360: E/AndroidRuntime(14322): at
> com.android.internal.os.ZygoteInit.main(ZygoteInit.java:775) 09-30
> 15:15:39.360: E/AndroidRuntime(14322): at
> dalvik.system.NativeStart.main(Native Method)
最佳答案
我可以看到您正在使用eclipse提供的有关DummyContent类的主详细信息流的示例，但是您已删除了这种和平的代码，这对于该代码的工作至关重要
setListAdapter(new ArrayAdapter<DummyContent.DummyItem>(getActivity(),
android.R.layout.simple_list_item_activated_1,
android.R.id.text1,
DummyContent.ITEMS));
把它放回onCreate
关于java - fragment 中的Asynctask后如何通知DataSetChanged，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/19094103/