java - 更改屏幕旋转时 ViewPager fragment 消失

Question

我正在开发包含 ViewPager 和 Fragment 的 android 应用程序，如下所示:

MainActivity(MainActivityFragment(screenSlideViewPager(Fragments)))，意思是:

Activity contains Fragment contains ViewPager contains fragment s

现在我的问题是当旋转设备或更改屏幕旋转时，ViewPager 中的所有 fragment 都消失了。

有解决这个问题的想法吗？

编辑 1

MainActivity.java:

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

    if (getSupportFragmentManager().findFragmentByTag(TAG) == null) {
        final FragmentTransaction ft = getSupportFragmentManager()
                .beginTransaction();
        ft.add(android.R.id.content, new MainActivityFragment(), TAG);
        ft.commit();
    }
}

MainActivityFragment.java:

public class MainActivityFragment extends Fragment {
    private ViewPager mPager = null;
    private PagerAdapter mPageAdapter = null;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        final View reVal = inflater.inflate(R.layout.activity_main, container, false);
        mPager = (ViewPager) reVal.findViewById(R.id.pagerMainContent);
        mPageAdapter = new ScreenSlidePagerAdapter(getActivity().getFragmentManager());
        mPager.setAdapter(mPageAdapter);
        return reVal;
    }

    private MainGridViewFragment mainGridFragment;
    private AlphabetGridViewFragment alphabetGridFragment;

    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
        public ScreenSlidePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public android.app.Fragment getItem(int position) {
            switch (position) {
                case 1:
                    mainGridFragment = new MainGridViewFragment();
                    return mainGridFragment;
                case 0:
                    alphabetGridFragment = new AlphabetGridViewFragment();
                    return alphabetGridFragment;
                default:
                    return null;
            }
        }

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

编辑 2

显然MainActivity和MainActivityFragment都被加载了，证明是ActionBar，另请注意，ViewPager 也已加载，因为您仍然可以在页面之间导航(蓝灯表示寻呼机已到达最后一页)但您看不到其内容。

Answer 1

看起来您的主要 Activity 正在使用 getSupportFragmentManager()，而您的 Fragment 正在使用 getFragmentManager()。

不确定这是否值得回复，但我的评分太低，无法以其他方式回复。 :)

编辑:我相信您可能还需要使用支持库扩展 FragmentActivity。

见:https://stackoverflow.com/a/10609839/2640693

编辑 2:

public class MainActivityFragment extends FragmentActivity {
    private ViewPager mPager = null;
    private PagerAdapter mPageAdapter = null;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        final View reVal = inflater.inflate(R.layout.activity_main, container, false);
        mPager = (ViewPager) reVal.findViewById(R.id.pagerMainContent);
        mPageAdapter = new ScreenSlidePagerAdapter(getChildFragmentManager());
        mPager.setAdapter(mPageAdapter);
        return reVal;
    }

    private MainGridViewFragment mainGridFragment;
    private AlphabetGridViewFragment alphabetGridFragment;

    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
        public ScreenSlidePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 1:
                    mainGridFragment = new MainGridViewFragment();
                    return (Fragment)mainGridFragment;
                case 0:
                    alphabetGridFragment = new AlphabetGridViewFragment();
                    return (Fragment)alphabetGridFragment;
                default:
                    return null;
            }
        }

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