ViewPager fragments of nested data blank page abnormal problem analysis

         开题思考：Fragment放ViewPager,ViewPager里面是fragment.第一次进入没问题,再次进入ViewPager的fragment时里面内容就没了,A data blank page exception occurs.

          描述：activityPut two inFragment,Pages to be reviewed respectively、Added page;which is pending reviewfragment中利用viewpager放了三个fragment,All respectively、审核加入、Audit exit,The second switch is pending review、已加入fragment时,will be found pending reviewfragment中ViewPager承载的FragmentData blank pages will appear.如下图所示：

         It feels like it is based on experienceFragmentManager出了问题,因为FragmentManagerThe responsibility is to be responsible for managementFragment,包括对Fragment栈中的Fragement进行添加,删除,替换等操作,Since there is a blank page,肯定是FragmentManager在进行FragmentNot working properly when replacing,查看Fragment以及FragmentActivityThere are three types of source code foundFragmentManager,分别为getFragmentManager、getSupportFragmentManager、getChildFragmentManager;其中getFragmentManager跟getChildFragmentManager在Fragment类中,而getSupportFragmentManager位于FragmentActivity中,而getFragmentManager虽然在Fragment中,But it is mentioned at the end of the official note,如果当前Fragment是另外一个Fragment的子类,则当前FragmentManager属于父类,这就意味着,Although the three are similar, the objects of management are different.

The source code of the three is as follows：

getFragmentManager:

    /**
     * Return the FragmentManager for interacting with fragments associated
     * with this fragment's activity.  Note that this will be non-null slightly
     * before {@link #getActivity()}, during the time from when the fragment is
     * placed in a {@link FragmentTransaction} until it is committed and
     * attached to its activity.
     *
     * <p>If this Fragment is a child of another Fragment, the FragmentManager
     * returned here will be the parent's {@link #getChildFragmentManager()}.
     */
    final public FragmentManager getFragmentManager() {
        return mFragmentManager;
    }

getSupportFragmentManager:

    /**
     * Return the FragmentManager for interacting with fragments associated
     * with this activity.
     */
    public FragmentManager getSupportFragmentManager() {
        return mFragments.getSupportFragmentManager();
    }

getChildFragmentManager:

    /**
     * Return a private FragmentManager for placing and managing Fragments
     * inside of this Fragment.
     */
    final public FragmentManager getChildFragmentManager() {
        if (mChildFragmentManager == null) {
            instantiateChildFragmentManager();
            if (mState >= RESUMED) {
                mChildFragmentManager.dispatchResume();
            } else if (mState >= STARTED) {
                mChildFragmentManager.dispatchStart();
            } else if (mState >= ACTIVITY_CREATED) {
                mChildFragmentManager.dispatchActivityCreated();
            } else if (mState >= CREATED) {
                mChildFragmentManager.dispatchCreate();
            }
        }
        return mChildFragmentManager;
    }

       根据google官方的描述（PS：EnglishSelf-translation is out of the question）,大意为getFragmentManager、跟getSupportFragmentManagerIs to get manageable and currentActivity有关联的Fragment的FragmentManager,That is to say, the two belong to each otherActivity的,再来看下getChildFragment的官方注释

    /**
     * Return a private FragmentManager for placing and managing Fragments
     * inside of this Fragment.
     */
    final public FragmentManager getChildFragmentManager() {
   

As mentioned in the title of the articleViewPager设置Adapter：

 viewPager.setAdapter(new ManageFragmentPagerAdapter(getFragmentManager(), list));

 viewPager.setAdapter(new ManageFragmentPagerAdapter(getChildFragmentManager(), list));