片段Inflater中的空指针异常

时间：2013-12-26 18:37:45

标签： java android android-layout android-fragments layout-inflater

我是java新手，我已经构建了一个使用片段的应用程序。每个选项卡都将项目作为本地sqllite数据库中的列表打开。

数据库打开正常，但我收到了inflater的指针错误。

加载子片段类的Frament类

public class Fragment2 extends SherlockFragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.viewpager_main, container, false);
        // Locate the ViewPager in viewpager_main.xml
        ViewPager mViewPager = (ViewPager) view.findViewById(R.id.viewPager);
        // Set the ViewPagerAdapter into ViewPager
        mViewPager.setAdapter(new ViewPagerAdapter(getChildFragmentManager()));
        return view;
    }

    @Override
    public void onDetach() {
        super.onDetach();
        try {
            Field childFragmentManager = Fragment.class
                    .getDeclaredField("mChildFragmentManager");
            childFragmentManager.setAccessible(true);
            childFragmentManager.set(this, null);
        } catch (NoSuchFieldException e) {
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }
}

从我的子片段

获取数据的ListViewAdapter.java类 
public class ListViewAdapter extends SimpleCursorAdapter {

    // Declare Variables
    Context context;
    int rank;
    int[] flag;
    LayoutInflater inflater;

    public ListViewAdapter(Context context, int layout, Cursor cursor, String[] from, int[] to, int rank) {
        super(context, layout , cursor, from, to);
        this.rank = rank;
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {

        // Create the idno textview with background image
        TextView idno = (TextView) view.findViewById(R.id.rank);
        idno.setText(cursor.getString(3));

        // create the material textview
        TextView materials = (TextView) view.findViewById(R.id.country);
        materials.setText(cursor.getString(1));
    }
    public int getCount() {
        return rank;
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    public View getView(int position, View convertView, ViewGroup parent) {

        // Declare Variables
        TextView txtrank;
        TextView txtcountry;
        ImageView imgflag;

        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View itemView = inflater.inflate(R.layout.listview_item, parent, false);

        // Locate the TextViews in listview_item.xml
        txtrank = (TextView) itemView.findViewById(R.id.rank);
        txtcountry = (TextView) itemView.findViewById(R.id.country);


        return itemView;
    }
}

和我的FragmentTab.java类从db

获取数据 
public class FragmentTab1 extends SherlockFragment {
       private static final String DB_NAME = "animalsDB.sqllite3";
        //������� ��������� �������� ������� ���� ����� �� �����������
        private static final String TABLE_NAME = "animals";
        private static final String FRIEND_ID = "_id";
        private static final String FRIEND_NAME = "name";
        private static final String FRIEND_GAME = "type";
        public static final String[] ALL_KEYS = new String[] {FRIEND_ID, FRIEND_NAME, FRIEND_GAME};

        private SQLiteDatabase database;

    int rank;
    int[] flag;
    ListView list;
    ListViewAdapter adapter;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragmenttab1, container,
                false);

        ExternalDbOpenHelper dbOpenHelper = new ExternalDbOpenHelper(getActivity(), DB_NAME);
        database = dbOpenHelper.openDataBase();
        //���, ���� �������!
        rank = (int) count();
            Cursor cursor = getAllRows();

            // Allow activity to manage lifetime of the cursor.
            // DEPRECATED! Runs on the UI thread, OK for small/short queries.
            getActivity().startManagingCursor(cursor);

            // Setup mapping from cursor to view fields:
            String[] fromFieldNames = new String[] 
                    {FRIEND_ID, FRIEND_NAME, FRIEND_GAME };
            int[] toViewIDs = new int[]
                    {    R.id.item_icon,   R.id.item_name,        R.id.item_game};

            list = (ListView) rootView.findViewById(R.id.listview);
            adapter = new ListViewAdapter(getActivity(), R.layout.fragmenttab1, cursor, fromFieldNames, toViewIDs, rank);
            // Binds the Adapter to the ListView
            list.setAdapter(adapter);       

            list.setOnItemClickListener(new OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView<?> parent, View view,
                        int position, long id) {
                        // Send single item click data to SingleItemView Class
                        Intent i = new Intent(getActivity(), SingleItemView.class);
                        // Pass all data rank
                        i.putExtra("rank", FRIEND_NAME);
                        // Pass all data country
                        i.putExtra("country", FRIEND_GAME);
                        // Pass a single position
                        i.putExtra("position", position);
                        // Open SingleItemView.java Activity
                        startActivity(i);

                }});
            return rootView;


    }


        public Cursor getAllRows() {
            String where = null;
            Cursor c =  database.query(true, TABLE_NAME, ALL_KEYS, 
                                where, null, null, null, null, null);
            if (c != null) {
                c.moveToFirst();
            }
            return c;
        }

        public long count() {
            return DatabaseUtils.queryNumEntries(database,"animals");
        }
    }

我得到的错误是在我的ListViewAdapter.java课程中

inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

错误日志：

12-26 13:32:07.056: E/AndroidRuntime(1389): FATAL EXCEPTION: main
12-26 13:32:07.056: E/AndroidRuntime(1389): java.lang.NullPointerException
12-26 13:32:07.056: E/AndroidRuntime(1389):     at kf.kaunozoo.ListViewAdapter.getView(ListViewAdapter.java:64)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.AbsListView.obtainView(AbsListView.java:2177)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.ListView.makeAndAddView(ListView.java:1840)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.ListView.fillDown(ListView.java:675)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.ListView.fillFromTop(ListView.java:736)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.ListView.layoutChildren(ListView.java:1655)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.AbsListView.onLayout(AbsListView.java:2012)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1589)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:678)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:349)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.View.layout(View.java:14289)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewGroup.layout(ViewGroup.java:4562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1976)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1730)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.Choreographer.doCallbacks(Choreographer.java:562)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.Choreographer.doFrame(Choreographer.java:532)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.os.Handler.handleCallback(Handler.java:730)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.os.Looper.loop(Looper.java:137)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at android.app.ActivityThread.main(ActivityThread.java:5103)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at java.lang.reflect.Method.invokeNative(Native Method)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at java.lang.reflect.Method.invoke(Method.java:525)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-26 13:32:07.056: E/AndroidRuntime(1389):     at dalvik.system.NativeStart.main(Native Method)

1 个答案:

答案 0 :(得分：2)

Context context永远不会在Adapter类中初始化。因此，您得到NullPointerException。

将其初始化为

Context context;
    int rank;
    int[] flag;
    LayoutInflater inflater;

    public ListViewAdapter(Context context, int layout, Cursor cursor, String[] from, int[] to, int rank) {
        super(context, layout , cursor, from, to);
        this.rank = rank;
        this.context = context; //missing
    }
相关问题
最新问题