老师您好，我在学习4-5时，遇到如标题所示问题。视频中点击是有效果的（点击时颜色变深）。

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <!--在xml布局中，可以通过android:outlineProvider来指定轮廓的判定方式：

    none 即使设置了Z属性，也不会显示阴影
    background 会按照背景来设置阴影形状
    bounds 会按照View的大小来描绘阴影
    paddedBounds 和bounds类似，不过阴影会稍微向右偏移一点-->
    <!--tools:targetApi="lollipop" 忽略掉其上2属性 4.4以下-->
    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/appbar"
        android:elevation="@dimen/len_2"
        android:outlineProvider="bounds"
        tools:targetApi="lollipop"
        android:layout_width="match_parent"
        android:layout_height="@dimen/actionBarWithStatusBarSize"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toTopOf="parent">
        <!--framelayout占内存极少-->
        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginTop="@dimen/statusBarSize"
            android:paddingLeft="@dimen/len_4"
            android:paddingRight="@dimen/len_4">

            <com.huaying.common.widget.PortraitView
                android:id="@+id/pv_portrait"
                android:padding="@dimen/len_4"
                android:layout_width="@dimen/len_40"
                android:layout_height="@dimen/len_40"
                android:layout_margin="@dimen/len_4"
                android:foreground="@drawable/ic_touch_menu"
                android:clickable="true"
                android:src="@drawable/default_portrait"
                android:scaleType="centerCrop"/>

            <TextView
                android:id="@+id/tv_title"
                android:textColor="@color/white"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:gravity="center"
                android:layout_gravity="center"
                style="@style/TextAppearance.Title"
                android:text="@string/app_name"/>

            <ImageView
                android:scaleType="centerInside"
                android:id="@+id/iv_search"
                android:tint="?attr/toolbarMenuIconColor"
                android:padding="@dimen/len_10"
                android:layout_width="@dimen/len_40"
                android:layout_height="@dimen/len_40"
                android:contentDescription="@string/app_name"
                android:src="@drawable/ic_search"
                android:foreground="@drawable/ic_touch_menu"
                android:layout_gravity="end|center_vertical"/>
        </FrameLayout>

    </com.google.android.material.appbar.AppBarLayout>

    <FrameLayout
        android:id="@+id/fl_container"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        app:layout_constraintTop_toBottomOf="@id/appbar"
        app:layout_constraintBottom_toTopOf="@+id/navigation"/>

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="@dimen/len_52"
        android:layout_gravity="bottom"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:background="@color/grey_200"/>

    <net.qiujuer.genius.ui.widget.FloatActionButton
        android:id="@+id/fab_action"
        android:tint="@color/white"
        android:padding="@dimen/len_20"
        app:gBackgroundColor="@color/colorAccent"
        android:src="@drawable/ic_group_add"
        android:layout_width="@dimen/len_52"
        android:layout_height="@dimen/len_52"
        app:layout_anchor="@id/fl_container"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="@id/fl_container"
        app:layout_anchorGravity="bottom|end"
        android:layout_marginEnd="@dimen/len_16"
        android:layout_marginBottom="@dimen/len_16"/>
</androidx.constraintlayout.widget.ConstraintLayout>