I wanna show ToolBar ahead of the fragment, however, it doesn’t show at runtime. Although I tried to remove the fragment, it doesn’t show ToolBar. I can’t find any information about this problem on the Internet.

The following codes are layout_content.xml and layout_content.xml.

1. layout_content.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layout_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.google.android.material.appbar.MaterialToolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="@android:color/white"
        android:elevation="4dp">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <ImageView
                android:id="@+id/image_drawer"
                android:layout_width="15dp"
                android:layout_height="15dp"
                android:layout_centerVertical="true"
                android:src="@drawable/ic_density_medium" />

            <TextView
                android:id="@+id/text_header"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:layout_marginStart="12dp"
                android:layout_toEndOf="@+id/image_drawer"
                android:text="Standard"
                android:textColor="@color/black"
                android:textSize="25sp"
                android:textStyle="bold" />

            <ImageView
                android:id="@+id/image_history"
                android:layout_width="25dp"
                android:layout_height="25dp"
                android:layout_alignParentEnd="true"
                android:layout_centerVertical="true"
                android:layout_marginEnd="12dp"
                android:contentDescription="To show the history"
                android:src="@drawable/ic_history" />
        </RelativeLayout>
    </com.google.android.material.appbar.MaterialToolbar>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/fragmentContainerView"
            android:name="com.example.calculator.standard.StandardFragment"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </LinearLayout>

</LinearLayout>

2. layout_content.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/white"
    tools:context=".MainActivity"
    tools:openDrawer="start">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <include
            android:id="@+id/content"
            layout="@layout/layout_content"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_alignParentTop="true" />
    </LinearLayout>

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/navigationView"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/drawer" />
</androidx.drawerlayout.widget.DrawerLayout>

I’m new in android so i don’t really understand the problem.