ViewPager的碎片的看法时丢失ViewPager的母公司片段隐藏的则显示 [英] ViewPager's Fragment's view lost when ViewPager's parent Fragment hidden then shown

问题描述

我已经看到一些奇怪的行为与我ViewPager连同我自己FragmentStatePagerAdapter。

I've been seeing some strange behavior with my ViewPager along with my own FragmentStatePagerAdapter.

我视图层次结构是这样的：

My View hierarchy goes like this:

-> (1) Fragment root view (RelativeLayout)
 -> (2) ViewPager
  -> (3) ViewPager's current fragment view

在该片段，负责该片段根视图（1）获取隐藏（使用.hide（）的一个片段的事务），然后显示（与.show（）），该片段看法是当前显示的是ViewPager（3）变为零，虽然片段仍然存在。基本上，我ViewPager变得完全空白/透明。

When the Fragment that is responsible for the Fragment root view (1) gets hidden (using .hide() in a fragment transaction) and then shown (with .show()), the fragment view that was currently showing in the ViewPager (3) becomes null, although the fragment still exists. Basically, my ViewPager becomes completely blank/transparent.

我已经找到解决这个问题的唯一方法是调用

The only way I have found to fix this is to call

int current = myViewPager.getCurrentItem();
myViewPager.setAdapter(myAdapter);
myViewPager.setCurrentItem(current);

父片段见后。这在某种程度上触发意见重新创建，并显示在屏幕上。不幸的是，这偶尔会导致与寻呼机适配器调用 unregisterDataSetObserver（）两次的老观察员处理例外。

after the parent fragment is shown. This somehow triggers the views to be recreated and appear on screen. Unfortunately, this occasionally causes exceptions dealing with the pager adapter calling unregisterDataSetObserver() twice on an old observer.

有没有更好的方式来做到这一点？我想我所问的是：

Is there a better way to do this? I guess what I am asking is:

为什么在我的ViewPager我的片段观点被破坏掉了，当ViewPager的父片段是隐藏的？

更新：这也发生在应用程序最小化，然后选择恢复（由pressing家里动作键，然后返回）

Update: this also happens when the application is "minimized" and then "restored" (by pressing the home action key and then returning).

每个请求，这里是我的传呼机适配器类：

Per request, here's my pager adapter class:

public class MyInfoSlidePagerAdapter extends FragmentStatePagerAdapter {

    private ArrayList<MyInfo> infos = new ArrayList<MyInfo>();

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

    public MyInfoSlidePagerAdapter (FragmentManager fm, MyInfo[] newInfos) {
        super(fm);
        setInfos(newInfos);
    }

    @Override
    public int getItemPosition(Object object) {
        int position = infos.indexOf(((MyInfoDetailsFragment)object).getMyInfo());
        return position > 0 ? position : POSITION_NONE;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return infos.get(position).getName();
    }

    @Override
    public Fragment getItem(int i) {
        return infos.size() > 0 ? MyInfoDetailsFragment.getNewInstance(infos.get(i)) : null;
    }

    @Override
    public int getCount() {
        return infos.size();
    }

    public Location getMyInfoAtPosition(int i) {
        return infos.get(i);
    }

    public void setInfos(MyInfo[] newInfos) {
        infos = new ArrayList<MyInfo>(Arrays.asList(newInfos));
    }

    public int getPositionOfMyInfo(MyInfo info) {
        return infos.indexOf(info);
    }
}

我改名一些变量，但是除此之外，它正是我。

I've renamed some variables but other than that it is exactly what I have.

推荐答案

你不提供针对您的具体问题足够的信息，让我建立了一个示例项目，试图重现您的问题：应用程序有一个持有活动这种布局在一个相对布局及以下片段（ PagerFragment ）我有一个按钮，隐藏和放大器;显示上述 PagerFragment 。 PagerFragment 有一个 ViewPager ，并在寻呼机适配器每个片段只显示一个标签 - 该片段被命名为 DataFragment 。标签列表在父活动创造并传递给PagerFragment，然后通过转接器每个 DataFragment 。更改 PagerFragment 的知名度做没有问题，每一次它变得可见这又显示了previous所示的标签。

You're not providing enough info for your specific issue, so I built a sample project that tries to reproduce your issue: the app has an activity that holds a fragment (PagerFragment) within a relative layout and below this layout I have a button that hides & shows above PagerFragment. PagerFragment has a ViewPager and each fragment within pager adapter simply displays a label - this fragment is named DataFragment. The label list is created in parent activity and passed to PagerFragment and then through its adapter to each DataFragment. Changing the PagerFragment visibility is done with no issues and each time it's becoming visible again it shows the previous shown label.

问题的关键： 使用<一个href="http://developer.android.com/reference/android/support/v4/app/Fragment.html#getChildFragmentManager%28%29">Fragment#getChildFragmentManager()当你创建viewpager适配器，而不是getFragmentManager！

The key of the issue: Use Fragment#getChildFragmentManager() when you're creating the viewpager adapter and not getFragmentManager!

也许你可以与你所拥有的这个简单的项目进行比较，检查哪里的差异。所以在这里不用（自上而下）：

Maybe you can compare this simple project with what you have and check where are the differences. So here goes (top-down):

PagerActivity （在项目中唯一的活动）：

PagerActivity (the only activity in the project):

public class PagerActivity extends FragmentActivity {

    private static final String PAGER_TAG = "PagerActivity.PAGER_TAG";

    @Override
    protected void onCreate(Bundle savedInstance) {
        super.onCreate(savedInstance);
        setContentView(R.layout.pager_activity);
        if (savedInstance == null) {
            PagerFragment frag = PagerFragment.newInstance(buildPagerData());
            FragmentManager fm = getSupportFragmentManager();
            fm.beginTransaction().add(R.id.layout_fragments, frag, PAGER_TAG).commit();
        }
        findViewById(R.id.btnFragments).setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                changeFragmentVisibility();
            }
        });
    }

    private List<String> buildPagerData() {
        ArrayList<String> pagerData = new ArrayList<String>();
        pagerData.add("Robert de Niro");
        pagerData.add("John Smith");
        pagerData.add("Valerie Irons");
        pagerData.add("Metallica");
        pagerData.add("Rammstein");
        pagerData.add("Zinedine Zidane");
        pagerData.add("Ronaldo da Lima");
        return pagerData;
    }

    protected void changeFragmentVisibility() {
        Fragment frag = getSupportFragmentManager().findFragmentByTag(PAGER_TAG);
        if (frag == null) {
            Toast.makeText(this, "No PAGER fragment found", Toast.LENGTH_SHORT).show();
            return;
        }
        boolean visible = frag.isVisible();
        Log.d("APSampler", "Pager fragment visibility: " + visible);
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        if (visible) {
            ft.hide(frag);
        } else {
            ft.show(frag);
        }
        ft.commit();
        getSupportFragmentManager().executePendingTransactions();
    }
}

其布局文件的 pager_activity.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="4dp" >

    <Button
        android:id="@+id/btnFragments"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Hide/Show fragments" />

    <RelativeLayout
        android:id="@+id/layout_fragments"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/btnFragments"
        android:layout_marginBottom="4dp" >
    </RelativeLayout>

</RelativeLayout>

注意，我加入 PagerFragment 活动时首先显示的是 - 和 PagerFragment 类：

Observe that I am adding the PagerFragment when the activity is first shown - and the PagerFragment class:

public class PagerFragment extends Fragment {

    private static final String DATA_ARGS_KEY = "PagerFragment.DATA_ARGS_KEY";

    private List<String> data;

    private ViewPager pagerData;

    public static PagerFragment newInstance(List<String> data) {
        PagerFragment pagerFragment = new PagerFragment();
        Bundle args = new Bundle();
        ArrayList<String> argsValue = new ArrayList<String>(data);
        args.putStringArrayList(DATA_ARGS_KEY, argsValue);
        pagerFragment.setArguments(args);
        return pagerFragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        data = getArguments().getStringArrayList(DATA_ARGS_KEY);
    }

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

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        pagerData = (ViewPager) view.findViewById(R.id.pager_data);
        setupPagerData();
    }

    private void setupPagerData() {
        PagerAdapter adapter = new LocalPagerAdapter(getChildFragmentManager(), data);
        pagerData.setAdapter(adapter);
    }

}

其布局（只有ViewPager这需要全尺寸）：

its layout (only the ViewPager that takes full size):

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

和它的适配器：

public class LocalPagerAdapter extends FragmentStatePagerAdapter {
    private List<String> pagerData;

    public LocalPagerAdapter(FragmentManager fm, List<String> pagerData) {
        super(fm);
        this.pagerData = pagerData;
    }

    @Override
    public Fragment getItem(int position) {
        return DataFragment.newInstance(pagerData.get(position));
    }

    @Override
    public int getCount() {
        return pagerData.size();
    }
}

此适配器创建一个 DataFragment 的每一页：

This adapter creates a DataFragment for each page:

public class DataFragment extends Fragment {
    private static final String DATA_ARG_KEY = "DataFragment.DATA_ARG_KEY";

    private String localData;

    public static DataFragment newInstance(String data) {
        DataFragment df = new DataFragment();
        Bundle args = new Bundle();
        args.putString(DATA_ARG_KEY, data);
        df.setArguments(args);
        return df;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        localData = getArguments().getString(DATA_ARG_KEY);
    }

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

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        view.findViewById(R.id.btn_page_action).setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                Toast.makeText(getActivity(), localData, Toast.LENGTH_SHORT).show();
            }
        });
        ((TextView) view.findViewById(R.id.txt_label)).setText(localData);
    }
}

和 DataFragment 的布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="4dp" >

    <Button
        android:id="@+id/btn_page_action"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="Interogate" />

    <TextView
        android:id="@+id/txt_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

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