更改屏幕旋转时 ViewPager 片段消失

2022-01-19 00:00:00 android android-fragments android-viewpager java

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

I'm working on android application that contains ViewPager with Fragments, like this:

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

MainActivity(MainActivityFragment(screenSlideViewPager(Fragments))), which means:

Activity contains Fragment contains ViewPager contains 片段s

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

Now my problem is when rotate device or change screen rotation all Fragments in ViewPager are disappear.

有解决这个问题的想法吗?

any ideas to solve this issue?

编辑 1

MainActivity.java:

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:

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.

Obviously MainActivity and MainActivityFragment are loaded, and the proof is The ActionBar, notice also that ViewPager is loaded too, because you still can navigate between pages (the blue light means that the pager reached to last page) but you can't see its content.

推荐答案

看起来您的主要活动正在使用 getSupportFragmentManager()，而您的 Fragment 正在使用 getFragmentManager().

It looks like your main activity is using the getSupportFragmentManager() while your fragment is using 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.:)

Not sure if this is worthy of an answer post but my rating is too low to reply any other way. :)

我相信您可能还需要使用支持库扩展 FragmentActivity.

I believe you may also need to extend a FragmentActivity with the support library.

参见: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;
        }
    }
}

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