Why does the toolbar disappear when the background of the fragment is set to a certain color?

I'm working on a drawer layout. I want to replace the main activity screen with a fragment when I click a menu item, but it doesn't show a toolbar when I set the background of a fragment on some color app. Work done so far ...

<!-- activity_main.xml-->  

<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout
    android:id="@+id/drawer"
    tools:openDrawer="start"
    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">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        >
        <androidx.appcompat.widget.Toolbar
            android:background="#ff9100"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:title="News Time"
            android:id="@+id/toolbar"
            />
        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/replacer"
            />
    </RelativeLayout>

    <com.google.android.material.navigation.NavigationView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/navmenu"
        app:menu="@menu/menu"
        app:headerLayout="@layout/navheader"
        android:layout_gravity="start"
        android:background="#ffaa00"
        />
</androidx.drawerlayout.widget.DrawerLayout>

MainActivity.java

package com.example.newsapp;

import androidx.annotation.NonNull;
import androidx.appcompat.app.ActionBarDrawerToggle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.drawerlayout.widget.DrawerLayout;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentTransaction;

import android.os.Bundle;
import android.view.MenuItem;
import android.widget.Toast;

import com.google.android.material.navigation.NavigationView;

public class MainActivity extends AppCompatActivity {

    NavigationView nav;
    ActionBarDrawerToggle toggle;
    DrawerLayout drawerLayout;

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

        Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        nav = (NavigationView)findViewById(R.id.navmenu);
        drawerLayout = (DrawerLayout)findViewById(R.id.drawer);

        toggle = new ActionBarDrawerToggle(this,drawerLayout,toolbar,R.string.open,R.string.close);
        drawerLayout.addDrawerListener(toggle);
        toggle.syncState();

         final FragmentManager fragmentManager = getSupportFragmentManager();
         final FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();


        nav.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
                Fragment temp = null;
                switch (menuItem.getItemId())
                {
                    case R.id.sporticon:
                        Toast.makeText(getApplicationContext(),"This is sport section",Toast.LENGTH_SHORT).show();
                        temp = new sportfragment();
                        break;
                }
                fragmentTransaction.replace(R.id.replacer,temp);
                fragmentTransaction.commit();
                return true;
            }
        });

    }
}

This is fine when there is no background attribute but toolbar disappears when I add it

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".sportfragment"
    android:background="#00c3ff"
    >

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_gravity="center"
        android:textSize="30sp"
        android:textColor="@android:color/black"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="This is sport section"
   />
</FrameLayout>