使用SlideMenu开发Android应用时遇到了一些问题。我要制作一个名为“BeritaTerbaru”的片段，但我在logcat中遇到了新的异常。 这是代码：
public class BeritaTerbaru extends Fragment {
// All variables
XMLParser parser;
Document doc;
String xml;
ListView lv;
ListViewAdapter adapter;
ArrayList<HashMap<String, String>> menuItems;
ProgressDialog pDialog;
private String URL = "http://api.androidhive.info/list_paging/?page=1";
// XML node keys
static final String KEY_ITEM = "item"; // parent node
static final String KEY_ID = "id";
static final String KEY_NAME = "name";
// Flag for current page
int current_page = 1;
public void onStart(){
super.onStart();
lv = (ListView) getView().findViewById(R.id.list);
menuItems = new ArrayList<HashMap<String, String>>();
new loadMoreListView().execute();
// LoadMore button
Button btnLoadMore = new Button(getActivity());
btnLoadMore.setText("Load More");
// Adding Load More button to lisview at bottom
lv.addFooterView(btnLoadMore);
// Getting adapter
adapter = new ListViewAdapter(getActivity(), menuItems);
lv.setAdapter(adapter);
/**
* Listening to Load More button click event
* */
btnLoadMore.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// Starting a new async task
new loadMoreListView().execute();
}
});
/**
* Listening to listview single row selected
* **/
lv.setOnItemClickListener(new 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();
// Starting new intent
Intent in = new Intent(getActivity(),
SingleMenuItemActivity.class);
in.putExtra(KEY_NAME, name);
startActivity(in);
}
});
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_beritaterbaru,container,false);
return view;
}
/**
* Async Task that send a request to url
* Gets new list view data
* Appends to list view
* */
private class loadMoreListView extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Please wait..");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show();
}
protected Void doInBackground(Void... unused) {
// increment current page
current_page += 1;
// Next page request
URL = "http://api.androidhive.info/list_paging/?page=" + current_page;
xml = parser.getXmlFromUrl(URL); // getting XML
doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
// looping through all item nodes <item>
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_NAME, parser.getValue(e, KEY_NAME));
// adding HashList to ArrayList
menuItems.add(map);
}
return null;
}
protected void onPostExecute(Void unused) {
// closing progress dialog
pDialog.dismiss();
// get listview current position - used to maintain scroll position
int currentPosition = lv.getFirstVisiblePosition();
// Appending new data to menuItems ArrayList
adapter = new ListViewAdapter(getActivity(),
menuItems);
lv.setAdapter(adapter);
// Setting new scroll position
lv.setSelectionFromTop(currentPosition + 1, 0);
}
}
}
这是log cat：
06-25 00:33:00.700: E/AndroidRuntime(895): FATAL EXCEPTION: AsyncTask #1
06-25 00:33:00.700: E/AndroidRuntime(895): Process: info.androidhive.slidingmenu, PID: 895
06-25 00:33:00.700: E/AndroidRuntime(895): java.lang.RuntimeException: An error occured while executing doInBackground()
06-25 00:33:00.700: E/AndroidRuntime(895): at android.os.AsyncTask$3.done(AsyncTask.java:300)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
06-25 00:33:00.700: E/AndroidRuntime(895): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.lang.Thread.run(Thread.java:841)
06-25 00:33:00.700: E/AndroidRuntime(895): Caused by: java.lang.NullPointerException
06-25 00:33:00.700: E/AndroidRuntime(895): at info.androidhive.slidingmenu.BeritaTerbaru$loadMoreListView.doInBackground(BeritaTerbaru.java:127)
06-25 00:33:00.700: E/AndroidRuntime(895): at info.androidhive.slidingmenu.BeritaTerbaru$loadMoreListView.doInBackground(BeritaTerbaru.java:1)
06-25 00:33:00.700: E/AndroidRuntime(895): at android.os.AsyncTask$2.call(AsyncTask.java:288)
06-25 00:33:00.700: E/AndroidRuntime(895): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
06-25 00:33:00.700: E/AndroidRuntime(895): ... 4 more
06-25 00:33:00.830: W/EGL_emulation(895): eglSurfaceAttrib not implemented
06-25 00:33:01.180: W/EGL_emulation(895): eglSurfaceAttrib not implemented
06-25 00:33:01.380: I/Choreographer(895): Skipped 37 frames! The application may be doing too much work on its main thread.
06-25 00:33:02.270: I/Choreographer(895): Skipped 52 frames! The application may be doing too much work on its main thread.
06-25 00:33:02.940: E/WindowManager(895): android.view.WindowLeaked: Activity info.androidhive.slidingmenu.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b4fa1328 V.E..... R......D 0,0-383,96} that was originally added here
06-25 00:33:02.940: E/WindowManager(895): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:346)
06-25 00:33:02.940: E/WindowManager(895): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:248)
06-25 00:33:02.940: E/WindowManager(895): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
06-25 00:33:02.940: E/WindowManager(895): at android.app.Dialog.show(Dialog.java:286)
06-25 00:33:02.940: E/WindowManager(895): at info.androidhive.slidingmenu.BeritaTerbaru$loadMoreListView.onPreExecute(BeritaTerbaru.java:117)
06-25 00:33:02.940: E/WindowManager(895): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
06-25 00:33:02.940: E/WindowManager(895): at android.os.AsyncTask.execute(AsyncTask.java:535)
06-25 00:33:02.940: E/WindowManager(895): at info.androidhive.slidingmenu.BeritaTerbaru.onStart(BeritaTerbaru.java:49)
06-25 00:33:02.940: E/WindowManager(895): at android.app.Fragment.performStart(Fragment.java:1724)
06-25 00:33:02.940: E/WindowManager(895): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:918)
06-25 00:33:02.940: E/WindowManager(895): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
06-25 00:33:02.940: E/WindowManager(895): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1044)
06-25 00:33:02.940: E/WindowManager(895): at android.app.FragmentManagerImpl.dispatchStart(FragmentManager.java:1858)
06-25 00:33:02.940: E/WindowManager(895): at android.app.Activity.performStart(Activity.java:5259)
06-25 00:33:02.940: E/WindowManager(895): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2149)
06-25 00:33:02.940: E/WindowManager(895): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
06-25 00:33:02.940: E/WindowManager(895): at android.app.ActivityThread.access$700(ActivityThread.java:135)
06-25 00:33:02.940: E/WindowManager(895): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
06-25 00:33:02.940: E/WindowManager(895): at android.os.Handler.dispatchMessage(Handler.java:102)
06-25 00:33:02.940: E/WindowManager(895): at android.os.Looper.loop(Looper.java:137)
06-25 00:33:02.940: E/WindowManager(895): at android.app.ActivityThread.main(ActivityThread.java:4998)
06-25 00:33:02.940: E/WindowManager(895): at java.lang.reflect.Method.invokeNative(Native Method)
06-25 00:33:02.940: E/WindowManager(895): at java.lang.reflect.Method.invoke(Method.java:515)
06-25 00:33:02.940: E/WindowManager(895): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
06-25 00:33:02.940: E/WindowManager(895): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
06-25 00:33:02.940: E/WindowManager(895): at dalvik.system.NativeStart.main(Native Method)
我有另一个支持类，如XMLParser，ListViewAdapter，SingleListMenu和另一个片段类。但我认为我的错误在于这堂课。有人帮帮我吗？
答案 0 :(得分：0)
试试这个..
在onStart()内删除以下行
parser = new XMLParser();
xml = parser.getXmlFromUrl(URL); // getting XML
doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
// looping through all item nodes <item>
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)); // id not using any where
map.put(KEY_NAME, parser.getValue(e, KEY_NAME));
// adding HashList to ArrayList
menuItems.add(map);
}
并添加
new loadMoreListView().execute();
同时您无法在doInBackground内进行用户更新，如下所示更改AsyncTask
private class loadMoreListView extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Please wait..");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show();
}
protected Void doInBackground(Void... unused) {
// increment current page
current_page += 1;
// Next page request
URL = "http://api.androidhive.info/list_paging/?page=" + current_page;
parser = new XMLParser();
xml = parser.getXmlFromUrl(URL); // getting XML
doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_ITEM);
// looping through all item nodes <item>
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_NAME, parser.getValue(e, KEY_NAME));
// adding HashList to ArrayList
menuItems.add(map);
}
}
protected void onPostExecute(Void unused) {
// closing progress dialog
pDialog.dismiss();
// get listview current position - used to maintain scroll position
int currentPosition = lv.getFirstVisiblePosition();
// Appending new data to menuItems ArrayList
adapter = new ListViewAdapter(getActivity(),
menuItems);
lv.setAdapter(adapter);
// Setting new scroll position
lv.setSelectionFromTop(currentPosition + 1, 0);
}
}