element-android/vector/src/main/res/layout/activity_call.xml

<?xml version="1.0" encoding="utf-8"?><!-- tools:ignore is needed because lint thinks this can be replaced with a merge. Replacing this
     with a merge causes the fullscreen SurfaceView not to be centered. -->
<androidx.constraintlayout.widget.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/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="?riotx_background"
    tools:ignore="MergeRootFrame">

    <org.webrtc.SurfaceViewRenderer
        android:id="@+id/fullscreen_video_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <org.webrtc.SurfaceViewRenderer
        android:id="@+id/pip_video_view"
        android:layout_width="wrap_content"
        android:layout_height="144dp"
        android:layout_gravity="bottom|end"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/participantNameText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/layout_horizontal_margin"
        android:layout_marginEnd="@dimen/layout_horizontal_margin"
        android:gravity="center"
        android:textColor="?riotx_text_primary"
        android:textSize="28sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toTopOf="@id/callTypeText"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        tools:text="@sample/matrix.json/data/displayName" />

    <TextView
        android:id="@+id/callTypeText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/layout_horizontal_margin"
        android:layout_marginEnd="@dimen/layout_horizontal_margin"
        android:layout_marginBottom="8dp"
        android:gravity="center"
        android:textColor="?riotx_text_secondary"
        android:textSize="22sp"
        app:layout_constraintBottom_toTopOf="@id/otherMemberAvatar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        tools:text="@string/action_video_call" />

    <ImageView
        android:id="@+id/otherMemberAvatar"
        android:layout_width="160dp"
        android:layout_height="160dp"
        android:contentDescription="@string/avatar"
        android:scaleType="centerCrop"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.3"
        tools:src="@tools:sample/avatars" />

    <TextView
        android:id="@+id/callStatusText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/layout_horizontal_margin"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="@dimen/layout_horizontal_margin"
        android:layout_marginBottom="8dp"
        android:gravity="center"
        android:textColor="?riotx_text_secondary"
        android:textSize="22sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/otherMemberAvatar"
        tools:text="@string/call_connecting" />

    <ProgressBar
        android:id="@+id/callConnectingProgress"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        android:visibility="gone"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/callStatusText"
        tools:visibility="visible" />

    <androidx.constraintlayout.widget.Group
        android:id="@+id/callInfoGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="visible"
        app:constraint_referenced_ids="participantNameText,callTypeText,otherMemberAvatar,callStatusText" />

    <androidx.constraintlayout.widget.Group
        android:id="@+id/callVideoGroup"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="visible"
        app:constraint_referenced_ids="pip_video_view, fullscreen_video_view"
        tools:visibility="invisible" />

    <im.vector.app.features.call.CallControlsView
        android:id="@+id/callControls"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent" />

    <FrameLayout
        android:id="@+id/hud_fragment_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout
            android:id="@+id/call_fragment_container"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </FrameLayout>

</androidx.constraintlayout.widget.ConstraintLayout>