如何在折叠的工具栏布局内隐藏工具栏？

Question

使用折叠的工具栏布局，使用图像模式实现了灵活的空间。我遇到的问题是工具栏无论处于折叠状态还是保持固定在顶部的状态。

    <?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <data>

    </data>

    <android.support.design.widget.CoordinatorLayout
        android:id="@+id/event_management_coordinator_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fitsSystemWindows="true"
        tools:context="com.butterflyinnovations.collpoll.postmanagement.share.event.eventManagement.EventManagementActivity">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/event_management_appbar"
            android:layout_width="match_parent"
            android:layout_height="200dp"
            android:theme="@style/AppTheme.AppBarOverlay">

            <android.support.design.widget.CollapsingToolbarLayout
                android:id="@+id/event_management_collapsing_toolbar"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fitsSystemWindows="true"
                app:contentScrim="?attr/colorPrimary"
                app:expandedTitleMarginEnd="64dp"
                app:expandedTitleMarginStart="48dp"
                app:layout_scrollFlags="scroll|enterAlways|exitUntilCollapsed"
                app:toolbarId="@id/toolbar">

                <ImageView
                    android:id="@+id/event_management_collapsing_image"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:contentDescription="@string/default_content_description"
                    android:fitsSystemWindows="true"
                    android:scaleType="centerCrop"
                    app:layout_collapseMode="parallax"
                    android:src="@color/blue"/>

                <android.support.v7.widget.Toolbar
                    android:id="@+id/toolbar"
                    android:layout_width="match_parent"
                    android:layout_height="?android:attr/actionBarSize"
                    app:contentInsetStartWithNavigation="0dp"
                    app:layout_collapseMode="pin"
                    app:layout_scrollFlags="scroll|enterAlways"
                    app:popupTheme="@style/AppTheme.PopupOverlay" />

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

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

        <FrameLayout
            android:id="@+id/event_management_frame_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

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

附加屏幕截图：添加的屏幕截图是上述xml的设计 Attached Screenshot of added XML

浏览了各种代码和教程。却找不到确切的担心原因。

更新

使用以下类作为侦听器：

public abstract class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {

public enum State {
    EXPANDED,
    COLLAPSED,
    IDLE
}

private State mCurrentState = State.IDLE;

@Override
public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
    if (i == 0) {
        if (mCurrentState != State.EXPANDED) {
            onStateChanged(appBarLayout, State.EXPANDED);
        }
        mCurrentState = State.EXPANDED;
    } else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
        if (mCurrentState != State.COLLAPSED) {
            onStateChanged(appBarLayout, State.COLLAPSED);
        }
        mCurrentState = State.COLLAPSED;
    } else {
        if (mCurrentState != State.IDLE) {
            onStateChanged(appBarLayout, State.IDLE);
        }
        mCurrentState = State.IDLE;
    }
}

public abstract void onStateChanged(AppBarLayout appBarLayout, State state);

}

并进行如下操作：

 activityEventManagementBinding.eventManagementAppbar.addOnOffsetChangedListener(object : AppBarStateChangeListener() {
        override fun onStateChanged(appBarLayout: AppBarLayout, state: AppBarStateChangeListener.State) {
            if (state == State.COLLAPSED) {
                supportActionBar!!.setBackgroundDrawable(ContextCompat.getDrawable(this@EventManagementActivity, R.color.primary_color))
            } else {
                supportActionBar!!.setBackgroundDrawable(ContextCompat.getDrawable(this@EventManagementActivity, R.color.caldroid_transparent))
            }
        }
    })