Android片段stackoverflow

时间：2013-10-07 07:21:59

标签： android android-fragments nullpointerexception android-viewpager

当我实例化这个片段时，我得到一个stackoverflow错误。我正在尝试使用我的主要活动类中定义的导航抽屉选择此片段。

public class MyFragment extends Fragment {

    public static MyFragment newInstance() {
        return new MyFragment();
    }

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

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.page_meet, container, false);
    }

    public void onViewCreated(View view, Bundle savedInstanceState) {
        ViewPager mViewPager = (ViewPager) view.findViewById(R.id.pager);
        MyFragmentPagerAdapter mViewPagerAdapter = new MyFragmentPagerAdapter(getChildFragmentManager());
        mViewPager.setAdapter(mViewPagerAdapter);
    }

    public class MyFragmentPagerAdapter extends FragmentPagerAdapter {

        public MyFragmentPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            return newInstance();
        }

        @Override
        public int getCount() {
            return 2;
        }
    }
}

这是XML文件page_meet.xml：

<android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout 
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:background="#00FF00" >


</LinearLayout>

</android.support.v4.view.ViewPager>

Logcat的信息量不大：

10-07 03:19:27.910: E/AndroidRuntime(27875): FATAL EXCEPTION: main
10-07 03:19:27.910: E/AndroidRuntime(27875): java.lang.StackOverflowError
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11890)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirection(View.java:11892)
10-07 03:19:27.910: E/AndroidRuntime(27875):    at android.view.View.canResolveLayoutDirec

2 个答案:

答案 0 :(得分：0)

我写了我的回答，却没有发现你在ViewPager的XML中有Fragment。你是否打算MyFragment包含其他Fragment？如果没有，那么这种设计是不正确的。 ViewPager属于Activity中使用的布局。如果您确实想在Fragment中展示其他MyFragment，请参阅here。

原始答案： 您的问题是，您要在MyFragmentPagerAdapter本身的onViewCreated中创建新的Fragment。寻呼机适配器不应该是Fragment的内部类。寻呼机适配器与Activity中的视图寻呼机配合使用，以确定在任何给定时间应显示哪种类型的Fragment。

编辑： 仅仅因为我看到您对其他答案的评论，getItem应该返回Fragment的新实例。这不是潜在的问题。

答案 1 :(得分：0)

感谢您的回答。我确实希望MyFragment包含一个填充了其他两个片段的ViewPager。堆栈溢出错误是因为我在没有意识到的情况下递归调用了MyFragment.newInstance（）。我尝试使用它自己的片段类填充视图分页器。我通过嵌套另一个片段类并在getItem（）中调用其newInstance（）方法来解决问题。

完成工作代码：

public class MyFragment extends Fragment {

    public static final MyFragment newInstance() {
        return new MyFragment();
    }

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.page_meet, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        ViewPager mViewPager = (ViewPager) view.findViewById(R.id.pager);
        MyFragmentPagerAdapter mViewPagerAdapter = new MyFragmentPagerAdapter(getChildFragmentManager());
        mViewPager.setAdapter(mViewPagerAdapter);
    }

    public class MyFragmentPagerAdapter extends FragmentPagerAdapter {

        public MyFragmentPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            return MeetFragment.newInstance(position);
        }

        @Override
        public int getCount() {
            return 2;
        }
    }

    public static class MeetFragment extends Fragment {
        public static final String ARG_POSITION = "position";

        public static final MeetFragment newInstance(int position) {
            MeetFragment fragment = new MeetFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_POSITION, position);
            fragment.setArguments(args);
            return fragment;
        }

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

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View rootView;
            int position = getArguments().getInt(ARG_POSITION);
            switch(position) {
            case 0:
                rootView = inflater.inflate(R.layout.page_meet_0, container, false);
                break;
            case 1:
                rootView = inflater.inflate(R.layout.page_meet_1, container, false);
                break;
            default:
                rootView = null;
                break;
            }
            return rootView;
        }
    }
}
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