折叠工具栏未显示标题文本

Question

我面临与折叠工具栏相关的奇怪问题。旋转屏幕时，折叠工具栏会在合同折叠工具栏时隐藏工具栏标题。

折叠工具栏展开时显示工具栏标题

请在此处屏蔽截图：https://imgur.com/a/99msG

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:expandedTitleMarginEnd="@dimen/collapsing_toolbar_title_margin_end"
            app:expandedTitleMarginStart="@dimen/collapsing_toolbar_title_margin_start"
            app:expandedTitleTextAppearance="@style/CollapsedAppBarTextAppearance"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <ImageView
                android:id="@+id/image"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:fitsSystemWindows="true"
                android:scaleType="centerCrop"
                android:src="@drawable/world_image"
                app:layout_collapseMode="parallax" />

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:minHeight="?android:attr/actionBarSize"
                app:layout_collapseMode="pin"/>

        </android.support.design.widget.CollapsingToolbarLayout>

    </android.support.design.widget.AppBarLayout>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/list_countries"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/background_color"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</android.support.design.widget.CoordinatorLayout>

Java代码：

public class CountryListFragment extends Fragment {

    @BindView(R.id.list_countries)
    RecyclerView mCountriesListRecyclerView;

    @BindView(R.id.toolbar)
    Toolbar mToolbar;

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

        //must bind for View Injection
        ButterKnife.bind(this, view);

        // register event bus to receive events
        EventBus.getDefault().register(this);

        ((AppCompatActivity) getActivity()).setSupportActionBar(mToolbar);

        initRecyclerView();
        populateRecyclerViewAdapter();
        return view;
    }

}

从外观上看，折叠工具栏会对设备的方向感到困惑，并向下设置工具栏的动画，而不是向上设置动画。