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="@color/bg_call_screen_blur"
    tools:ignore="MergeRootFrame">

    <ImageView
        android:id="@+id/bgCallView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:importantForAccessibility="no"
        android:scaleType="centerCrop"
        tools:src="@tools:sample/avatars" />

    <org.webrtc.SurfaceViewRenderer
        android:id="@+id/fullscreenRenderer"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/pipContainer"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@id/callControlsView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/callToolbar">

        <com.google.android.material.card.MaterialCardView
            android:id="@+id/pipRendererWrapper"
            android:layout_width="@dimen/call_pip_width"
            android:layout_height="@dimen/call_pip_height"
            android:layout_marginEnd="16dp"
            app:layout_goneMarginEnd="0dp"
            app:cardCornerRadius="@dimen/call_pip_radius"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent">

            <org.webrtc.SurfaceViewRenderer
                android:id="@+id/pipRenderer"
                android:layout_width="@dimen/call_pip_width"
                android:layout_height="@dimen/call_pip_height"
                android:visibility="gone"
                tools:visibility="visible" />

        </com.google.android.material.card.MaterialCardView>

        <com.google.android.material.card.MaterialCardView
            android:id="@+id/otherKnownCallLayout"
            android:layout_width="@dimen/call_pip_width"
            android:layout_height="@dimen/call_pip_height"
            android:layout_marginStart="16dp"
            android:layout_marginEnd="16dp"
            android:background="@color/element_background_light"
            android:foreground="?attr/selectableItemBackground"
            android:visibility="gone"
            app:cardBackgroundColor="@color/bg_call_screen"
            app:cardCornerRadius="@dimen/call_pip_radius"
            app:cardElevation="4dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@id/pipRendererWrapper"
            tools:visibility="visible">

            <ImageView
                android:id="@+id/otherKnownCallAvatarView"
                android:layout_width="64dp"
                android:layout_height="64dp"
                android:layout_gravity="center"
                android:importantForAccessibility="no"
                android:scaleType="centerCrop"
                tools:src="@tools:sample/avatars" />

            <ImageView
                android:id="@+id/otherSmallIsHeldIcon"
                android:layout_width="20dp"
                android:layout_height="20dp"
                android:layout_gravity="center"
                android:importantForAccessibility="no"
                android:src="@drawable/ic_call_small_pause" />

        </com.google.android.material.card.MaterialCardView>

    </androidx.constraintlayout.widget.ConstraintLayout>

    <com.google.android.material.appbar.MaterialToolbar
        android:id="@+id/callToolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        android:fitsSystemWindows="true"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navigationIcon="@drawable/ic_back_24dp"
        app:navigationIconTint="@color/element_background_light"
        app:subtitle="3:10"
        app:subtitleTextAppearance="@style/TextAppearance.Vector.Caption"
        app:subtitleTextColor="@color/element_background_light"
        app:title="Video call"
        app:titleMarginTop="16dp"
        app:titleTextAppearance="@style/TextAppearance.Vector.Body.Medium"
        app:titleTextColor="@color/element_background_light" />

    <ImageView
        android:id="@+id/otherMemberAvatar"
        android:layout_width="120dp"
        android:layout_height="120dp"
        android:contentDescription="@string/avatar"
        android:importantForAccessibility="no"
        android:scaleType="centerCrop"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        tools:src="@sample/user_round_avatars" />

    <ImageView
        android:id="@+id/smallIsHeldIcon"
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:importantForAccessibility="no"
        android:src="@drawable/ic_call_small_pause"
        app:layout_constraintBottom_toBottomOf="@id/otherMemberAvatar"
        app:layout_constraintEnd_toEndOf="@id/otherMemberAvatar"
        app:layout_constraintStart_toStartOf="@id/otherMemberAvatar"
        app:layout_constraintTop_toTopOf="@id/otherMemberAvatar" />

    <TextView
        android:id="@+id/participantNameText"
        style="@style/Widget.Vector.TextView.Title"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/layout_horizontal_margin"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="@dimen/layout_horizontal_margin"
        android:gravity="center"
        android:textColor="@android:color/white"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/otherMemberAvatar"
        tools:text="@sample/users.json/data/displayName" />

    <Button
        android:id="@+id/callActionText"
        style="@style/Widget.Vector.Button.Text"
        android:layout_width="wrap_content"
        android:layout_height="48dp"
        android:layout_margin="8dp"
        android:gravity="center"
        android:textColor="?colorSecondary"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/participantNameText"
        tools:text="@string/call_resume_action" />

    <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, otherMemberAvatar" />

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

</androidx.constraintlayout.widget.ConstraintLayout>