我在我的android应用程序中实现了一个底部导航视图。有五个碎片。然而，我有一个问题，每次我改变片段的内容重叠的工具栏。
底部导航视图的布局

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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=".DashboardActivity">
    <include layout="@layout/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </include>
    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_above="@+id/navigationView"
        android:layout_height="match_parent"
       />
    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigationView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="0dp"
        android:layout_marginStart="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:itemBackground="@android:color/white"
        app:itemIconTint="@color/cardview_dark_background"
        app:itemTextColor="@android:color/black"
        app:menu="@menu/navigation_menu"
        />
</android.support.constraint.ConstraintLayout>

其中一个片段布局的示例

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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:id="@+id/frameLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".AttendanceFragment">
    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.7" />
    <android.support.v7.widget.CardView
        android:id="@+id/cardView2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toTopOf="@+id/barrier3"
        app:layout_constraintEnd_toStartOf="@+id/guideline"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">
        <Spinner
            android:id="@+id/spinner_courses"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:paddingBottom="4dp"
            android:paddingTop="4dp"
            app:layout_constraintEnd_toStartOf="@+id/guideline"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
    </android.support.v7.widget.CardView>
    <TextView
        android:id="@+id/tv_time"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="12sp"
        app:layout_constraintBottom_toTopOf="@+id/barrier3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/guideline"
        app:layout_constraintTop_toTopOf="parent"
        tools:text="Date" />
    <android.support.design.widget.FloatingActionButton
        android:id="@+id/add_fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:layout_margin="16dp"
        android:src="@drawable/ic_add_icon"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"/>
    <!--<android.support.design.widget.FloatingActionButton
        android:id="@+id/floatingActionButton"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_marginBottom="4dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="4dp"
        android:clickable="true"
        app:srcCompat="@drawable/ic_more_vert_black_24dp"
        app:fabSize="mini"
        app:layout_constraintBottom_toBottomOf="@+id/textView3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/spinner"
        app:layout_constraintTop_toTopOf="parent"
        android:focusable="true" />-->
    <android.support.constraint.Barrier
        android:id="@+id/barrier3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="bottom"
        app:constraint_referenced_ids="cardView2,tv_time"
        tools:layout_editor_absoluteY="511dp" />
    <android.support.v7.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginTop="4dp"
        app:cardBackgroundColor="@color/colorMainBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/barrier3">
        <android.support.v7.widget.RecyclerView
            android:id="@+id/rv_register"
            android:layout_width="match_parent"
            android:layout_height="match_parent">
        </android.support.v7.widget.RecyclerView>
    </android.support.v7.widget.CardView>
</android.support.constraint.ConstraintLayout>

这是屏幕上重叠内容的样子