android - 当方向改变时处理来自 ViewPager 的 fragment

Question

从今天早上开始，我一直在尝试使用 viewpager 来处理屏幕旋转，我尝试了很多方法，我阅读了几乎所有关于此问题的帖子，但我无法找到我的问题。

问题

1. 当我更改方向时，它会删除 3 或 4 个页面，我必须向右滑动 3 或 4 次才能查看其他页面。从纵向更改为横向几乎每次都有效，没有页面被删除，但如果我从纵向变为横向，页面就会消失

我在一篇文章中读到，这是由于方向改变时 fragment 被破坏，我们需要使用 setRetainInstance(true);在创建里面修复这个问题，但它不起作用，我在这里遗漏了什么吗？

    public class SectionsPagerAdapter extends FragmentStatePagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        if (position <= (arraySize - 1)) {
            HashMap<String, String> data = computeQuestion(questoes[randomize.get(position)]);
            return PlaceholderFragment.newInstance(position + 1, data, tables[randomize.get(position)]);
        } else {
            return FragmentResultados.newInstance(position + 1);
        }
    }

    @Override
    public int getCount() {
        return arraySize + 1; // number of pages + ending page
    }

    @Override
    public CharSequence getPageTitle(int position) {
        switch (position) {
            case 0:
                return "SECTION 1";
            case 1:
                return "SECTION 2";
            case 2:
                return "SECTION 3";
            default:
                return String.valueOf(position);
        }
    }
    }

fragment

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

编辑

fragment

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

        mViewPager = (ViewPager) getActivity().findViewById(R.id.container);
        mSectionsPagerAdapter = new SectionsPagerAdapter(getChildFragmentManager());
        mViewPager.setAdapter(mSectionsPagerAdapter);
        return rootView;
    }

结果:IllegalStateException:FragmentManager 已在执行事务

Activity

 private static ViewPager mViewPager;
 private static FragmentStatePagerAdapter mSectionsPagerAdapter;  

      @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_exame2);
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);
    }

list

 <activity
        android:name=".Exame"
        android:label="@string/title_activity_exame"
        android:theme="@style/AppTheme"
        android:configChanges="keyboardHidden|orientation|screenSize"/>

activity_xml

<android.support.design.widget.CoordinatorLayout      xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="pt.condutorresponsavel.android.testescodigo.Exame">

<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v4.view.ViewPager
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

<ImageView
    android:id="@+id/arrowLeft"
    android:background="@color/colorPrimary"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/ic_first_page_white_24dp"
    android:paddingLeft="10dp"
    android:paddingTop="3dp"
    android:paddingRight="10dp"
    android:paddingBottom="3dp"
    android:onClick="toFirst"
   />

<ImageView
    android:background="@color/colorPrimary"
    android:onClick="toLast"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/ic_last_page_white_24dp"
    android:paddingLeft="10dp"
    android:paddingTop="3dp"
    android:paddingRight="10dp"
    android:paddingBottom="3dp"
    android:layout_alignParentRight="true"
    android:id="@+id/arrowRight" />

<TextView
    android:id="@+id/timeleft"
    android:textColor="#ffffff"
    android:background="@color/colorPrimary"
    android:paddingRight="10dp"
    android:paddingLeft="5dp"
    android:gravity="center"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="20:01"
    android:layout_alignBottom="@+id/arrowRight"
    android:layout_toLeftOf="@+id/arrowRight"
    android:layout_toStartOf="@+id/arrowRight"
    android:layout_alignParentTop="true" />

我将代码示例上传到 github

已修复

private void InitializeUI(){
    mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);

}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    setContentView(R.layout.activity_exame2);
    InitializeUI();
}

Answer 1

我在 list 文件中缺少 android:configChanges="orientation|screenSize" 。例如:

<activity
    android:name=".MyActivity"
    android:configChanges="orientation|screenSize" />