ListView在片段中不起作用

Fragment.java

public class Fragment_Main extends Fragment{ 
ArrayAdapter<String> categoryAdapter; 
ArrayList<String> categoryList = new ArrayList<String>(); 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
    Bundle savedInstanceState) { 
    View View = inflater.inflate(R.layout.fragment_main, container, false); 
    ListView list = (ListView) getView().findViewById(R.id.listView1); 
    categoryAdapter=new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, categoryList); 
    list.setAdapter(categoryAdapter); 
    showCategoryTask task=new showCategoryTask(); 
    task.execute(); 
     return View; 
} 

class showCategoryTask extends AsyncTask<Void, Void, Void> { 
     @Override 
     protected Void doInBackground(Void... params) { 
      try { 
       URL url = new URL("http://garyhui86.er-webs.com/index.xml"); 
       HttpURLConnection urlConn = 
            (HttpURLConnection)url.openConnection(); 
       if (urlConn.getResponseCode() == HttpURLConnection.HTTP_OK) { 
        DocumentBuilder builder = DocumentBuilderFactory 
          .newInstance().newDocumentBuilder(); 
        Document document = builder.parse(urlConn.getInputStream()); 
        NodeList nodeList = document.getElementsByTagName("Info"); 
        for (int i = 0; i < nodeList.getLength(); i++) { 
         NamedNodeMap attributes=nodeList.item(i).getAttributes(); 
         String category=attributes.getNamedItem("categoryName").getNodeValue(); 
         Log.i("ttt", category); 
         categoryList.add(category); 
        } 
       } 
       urlConn.disconnect(); 
      } catch (Exception e) { 
       e.printStackTrace(); 
      } 
      return null; 
     } 
     @Override 
     protected void onPostExecute(Void result) { 
      super.onPostExecute(result); 
      categoryAdapter.notifyDataSetChanged(); 
     } 
    } 
}

Error Log: 
04-27 15:39:02.568: E/AndroidRuntime(7826): FATAL EXCEPTION: main 
04-27 15:39:02.568: E/AndroidRuntime(7826): java.lang.RuntimeException: Unable to start activity ComponentInfo{hkpro.shopdada.com.summonboardinfo/hkpro.shopdada.com.summonboardinfo.MainActivity}: java.lang.NullPointerException 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.os.Handler.dispatchMessage(Handler.java:99) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.os.Looper.loop(Looper.java:137) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at java.lang.reflect.Method.invoke(Method.java:511) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at dalvik.system.NativeStart.main(Native Method) 
04-27 15:39:02.568: E/AndroidRuntime(7826): Caused by: java.lang.NullPointerException 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at hkpro.shopdada.com.summonboardinfo.Fragment_Main.onCreateView(Fragment_Main.java:39) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:938) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1115) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1478) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1164) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.Activity.performStart(Activity.java:5114) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2153) 
04-27 15:39:02.568: E/AndroidRuntime(7826):  ... 11 more

来源

2014-04-27 user3578548

Fragment_Main.java中的第39行是什么？ – Saggy

您也可以在ListFragment中查看一下 - http://developer.android.com/reference/android/app/ListFragment.html; D – MatheusJardimB

此行引起麻烦我想：

View View = inflater.inflate(R.layout.fragment_main, container, false); 
ListView list = (ListView) getView().findViewById(R.id.listView1);

不要使用getView()方法，通过ID查找视图。使用膨胀布局来代替：

View root = inflater.inflate(R.layout.fragment_main, container, false); 
ListView list = (ListView) root.findViewById(R.id.listView1);

这样做的原因是getView()只返回碎片查看是否onCreateView返回。

来源

2014-04-27 15:52:18

tbank you very much〜it's work – user3578548

使用膨胀的对象来查找'ListView'。

做这样的：

'的ListView列表=（ListView控件）inflated_layout_object.findViewById（R.id.listView1）;'

在这里为你inflated_layout_object是查看（你已经创建）。

来源

2014-04-27 16:13:37 Saggy

ListView在片段中不起作用

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