自定义CoordinatorLayout.Behavior在Framelayout片段下不起作用

Question

我正在尝试使用带有CollapsingToolbarLayout和自定义appBar标题的CoordinatorLayout来制作android应用。

所以我想使用自定义CoordinatorLayout.Behavior在片段内组织我的LinearLayout，以更改折叠工具栏上的布局。

我的activity.xml

<?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:layout_height="match_parent"
    android:layout_width="match_parent"
    android:fillViewport="true">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/categoryAppBar"
            android:layout_width="match_parent"
            android:layout_height="@dimen/app_bar_height"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

                <android.support.design.widget.CollapsingToolbarLayout
                    xmlns:android="http://schemas.android.com/apk/res/android"
                    xmlns:app="http://schemas.android.com/apk/res-auto"
                    android:id="@+id/categoryCollapsingToolbarLayout"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    app:contentScrim="?attr/colorPrimary"
                    app:layout_scrollFlags="scroll|exitUntilCollapsed">

                        <ImageView
                            xmlns:android="http://schemas.android.com/apk/res/android"
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:scaleType="centerCrop"
                            android:src="@drawable/thai_1024"
                            app:layout_collapseMode="parallax" />

                        <android.support.v7.widget.Toolbar
                            xmlns:app="http://schemas.android.com/apk/res-auto"
                            android:id="@+id/categoryToolbar"
                            android:layout_width="match_parent"
                            android:layout_height="?attr/actionBarSize"
                            android:minHeight="?attr/actionBarSize"
                            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
                            app:layout_collapseMode="pin" />

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

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

        <FrameLayout
            android:id="@+id/category_appbar_container"
            android:layout_width="match_parent"
            android:layout_height="@dimen/app_bar_height"
            android:elevation="@dimen/level_8">

        </FrameLayout>

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

活动分类

 @Override
 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_category);

        mtoolbar = (Toolbar) findViewById(R.id.categoryToolbar);
        setSupportActionBar(mtoolbar);

        String categoryId = intent.getExtras().getString("categoryId");
        CategoryViewModel categoryViewModel = ViewModelProviders.of(this, viewModelFactory).get(CategoryViewModel.class);
        categoryViewModel.init(categoryId);

        observeViewModel(categoryViewModel);
 }

private void startAppbarCategoryAppbarFragment() {
        categoryAppbarFragment = new CategoryAppbarFragment();

        FragmentManager fragmentManager = getSupportFragmentManager();
        fragmentManager.beginTransaction()
                .add(R.id.category_appbar_container, categoryAppbarFragment)
                .commit();

    }

    private void observeViewModel(final CategoryViewModel categoryViewModel) {
        // Observe Category Data
        categoryViewModel.getCategory().observe(this, new Observer<Category>() {
            @Override
            public void onChanged(@Nullable Category category) {
                // Update UI
                if (category != null) {
                    startAppbarCategoryAppbarFragment();
                } else {
                    Log.e(TAG, "Category Data is Null");
                }
            }
        });
    }

我的fragment_appbar.xml（我用于将布局充气到CategoryAppbarFragment中）

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="@dimen/app_bar_height"
    android:gravity="bottom"
    android:orientation="horizontal"
    app:layout_behavior="@string/collapsing_category_appbar_behavior">

    <ImageView
        android:id="@+id/appBarCategoryImage"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:layout_marginBottom="12dp"
        android:layout_marginLeft="12dp"
        android:layout_marginRight="12dp"
        android:background="@drawable/rounded_box"
        android:contentDescription="Category Image"/>

    <RelativeLayout
        android:id="@+id/appBarTextContainer"
        android:layout_width="wrap_content"
        android:layout_height="@dimen/app_bar_height"
        android:gravity="bottom"
        android:orientation="vertical">

        <TextView
            android:id="@+id/appBarCategoryTitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:text="Test CAt title"
            android:textColor="@color/colorAccent"
            android:textSize="18sp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/appBarCategorySubTitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:paddingBottom="12dp"
            android:text="fingerprint_icon_content_description" />
    </RelativeLayout>

</LinearLayout>

问题是，当我像这样使用collapsing_category_appbar_behavior时，它将无法正常工作。

但是，如果我将CategoryAppbarFragment取出并将<LinearLayout>直接放在activity.xml内，则效果很好。

那么如何使这种行为在片段<FrameLayout>中起作用？

谢谢！