Question

每当我旋转设备时，应用程序崩溃，我无法弄清楚原因。这是LogCat信息：

07-26 10:11:48.260: E/AndroidRuntime(25775): FATAL EXCEPTION: main
07-26 10:11:48.260: E/AndroidRuntime(25775): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cleanlist/com.cleanlist.MainActivity}: java.lang.NullPointerException
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2088)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2113)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3554)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread.access$800(ActivityThread.java:139)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1230)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.os.Handler.dispatchMessage(Handler.java:99)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.os.Looper.loop(Looper.java:137)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread.main(ActivityThread.java:4918)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at java.lang.reflect.Method.invokeNative(Native Method)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at java.lang.reflect.Method.invoke(Method.java:511)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at dalvik.system.NativeStart.main(Native Method)
07-26 10:11:48.260: E/AndroidRuntime(25775): Caused by: java.lang.NullPointerException
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.widget.ListView.setAdapter(ListView.java:466)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at com.cleanlist.MainActivity$DummySectionFragment.onCreateView(MainActivity.java:307)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1070)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1861)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:547)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1178)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.Activity.performStart(Activity.java:5058)
07-26 10:11:48.260: E/AndroidRuntime(25775):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2061)
07-26 10:11:48.260: E/AndroidRuntime(25775):    ... 12 more

以下是问题所在的代码部分，它将问题指向listView.setAdapter（listadapter）;

public static class DummySectionFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        public transient ListObject list;
        public static final String ARG_SECTION_NUMBER = "section_number";
        private View thisView;
        private MainActivity mainActivity;
        private CustomListAdapter listadapter;


        public DummySectionFragment() {
        }

        public DummySectionFragment(MainActivity act, CustomListAdapter adp, ListObject thisList)
        {
            list = thisList;
            mainActivity = act;
            listadapter = adp;
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
        {
                View rootView = inflater.inflate(R.layout.list_layout, container, false);

                final int whichList = getArguments().getInt(ARG_SECTION_NUMBER);

                listadapter = new CustomListAdapter(getActivity(), R.layout.list_row, list);
                ListView listView = (ListView)rootView.findViewById(R.id.listView);
                if (listView != null)
                    listView.setAdapter(listadapter);
                else
                    Log.e("wbbug","ListView is NULL");
                listView.setSelection(1);
                listView.setOnItemClickListener(new AdapterView.OnItemClickListener() 
                {
                    @Override
                    public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) 
                    {
                      Log.d("wbbug","List item click: " + position + "List size: " + list.size());

                    }
                });

            thisView = rootView;
            return rootView;
        }

Answer 1

ArrayAdapter getCount方法中存在空指针异常。所以很可能你的列表已经变为空。轮换时，活动将被重新创建，并且您的列表可能无法正确初始化。

Android应用程序在轮换时崩溃

1 个答案: