components/cronet/android/sample/res/layout/main_activity.xml

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

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragment_container"
        android:name="org.chromium.cronet_sample_apk.OptionsFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <!-- bottom navigation bar -->
    <LinearLayout
        android:id="@+id/nav_view"
        android:padding="10dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_alignParentBottom="true"
        android:background="?android:attr/windowBackground">
        <!--suppress HardcodedText -->
        <TextView
            android:id="@+id/navigation_home"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:drawableTop="@drawable/ic_action_home"
            android:text="Home"
            android:gravity="center_horizontal"
            android:layout_weight="1">
        </TextView>
        <!--suppress HardcodedText -->
        <TextView
            android:id="@+id/navigation_options_ui"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:drawableTop="@drawable/ic_flag"
            android:text="Options"
            android:gravity="center_horizontal"
            android:layout_weight="1">
        </TextView>
    </LinearLayout>
</RelativeLayout>