anotherim/src/main/res/layout/activity_rtp_session.xml

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="?color_background_secondary">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/app_bar_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:visibility="visible">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
                app:popupTheme="?popupOverlayStyle" />

            <TextView
                android:id="@+id/with"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@id/status"
                android:layout_marginLeft="16dp"
                android:layout_marginTop="0dp"
                android:layout_marginRight="16dp"
                android:layout_marginBottom="32dp"
                android:textAppearance="@style/TextAppearance.Conversations.Display2"
                android:textColor="@color/white"
                tools:text="Juliet Capulet" />

        </android.support.design.widget.AppBarLayout>

        <org.webrtc.SurfaceViewRenderer
            app:elevation="4dp"
            android:id="@+id/local_video"
            android:layout_width="@dimen/local_video_preview_width"
            android:layout_height="@dimen/local_video_preview_height"
            android:layout_below="@+id/app_bar_layout"
            android:layout_alignParentEnd="true"
            android:layout_alignParentRight="true"
            android:layout_marginTop="24dp"
            android:layout_marginEnd="24dp"
            android:layout_marginRight="24dp"
            android:visibility="gone" />

        <org.webrtc.SurfaceViewRenderer
            android:id="@+id/remote_video"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_below="@+id/app_bar_layout"
            android:layout_alignParentStart="true"
            android:layout_alignParentLeft="true"
            android:layout_alignParentBottom="true"
            android:visibility="gone" />


        <RelativeLayout
            android:layout_width="288dp"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true"
            android:layout_marginBottom="24dp">

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/reject_call"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentStart="true"
                android:layout_alignParentLeft="true"
                android:layout_centerVertical="true"
                android:layout_margin="16dp"
                android:src="@drawable/ic_call_end_white_48dp"
                android:visibility="gone"
                app:backgroundTint="@color/red700"
                app:elevation="4dp"
                app:fabCustomSize="72dp"
                app:maxImageSize="36dp"
                tools:visibility="visible" />

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/in_call_action_left"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:layout_margin="16dp"
                android:layout_toStartOf="@+id/end_call"
                android:layout_toLeftOf="@+id/end_call"
                android:visibility="gone"
                app:backgroundTint="?color_background_primary"
                app:elevation="4dp"
                app:fabSize="mini"
                app:tint="?attr/icon_tint" />

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/end_call"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerInParent="true"
                android:layout_margin="16dp"
                android:src="@drawable/ic_call_end_white_48dp"
                android:visibility="visible"
                app:backgroundTint="@color/red700"
                app:elevation="4dp"
                app:fabCustomSize="72dp"
                app:maxImageSize="36dp" />

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/in_call_action_right"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:layout_margin="16dp"
                android:layout_toEndOf="@+id/end_call"
                android:layout_toRightOf="@+id/end_call"
                android:visibility="gone"
                app:backgroundTint="?color_background_primary"
                app:elevation="4dp"
                app:fabSize="mini"
                app:tint="?attr/icon_tint" />


            <android.support.design.widget.FloatingActionButton
                android:id="@+id/accept_call"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentEnd="true"
                android:layout_alignParentRight="true"
                android:layout_centerVertical="true"
                android:layout_margin="16dp"
                android:src="@drawable/ic_call_white_48dp"
                android:visibility="gone"
                app:backgroundTint="@color/green700"
                app:elevation="4dp"
                app:fabCustomSize="72dp"
                app:maxImageSize="36dp"
                tools:visibility="visible" />
        </RelativeLayout>

    </RelativeLayout>
</layout>