examples/androidnativeapi/res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:padding="8dp"
  tools:context="org.webrtc.examples.androidnativeapi.MainActivity">

  <org.webrtc.SurfaceViewRenderer
    android:id="@+id/local_renderer"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:layout_margin="8dp"/>

  <org.webrtc.SurfaceViewRenderer
    android:id="@+id/remote_renderer"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:layout_margin="8dp"/>


  <LinearLayout
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="48dp"
    style="?android:attr/buttonBarStyle">

    <Button
      android:id="@+id/call_button"
      android:text="@string/call_button"
      style="?android:attr/buttonBarButtonStyle"
      android:layout_width="0dp"
      android:layout_height="48dp"
      android:layout_weight="1"
      android:layout_margin="8dp"/>

    <Button
      android:id="@+id/hangup_button"
      android:text="@string/hangup_button"
      style="?android:attr/buttonBarButtonStyle"
      android:layout_width="0dp"
      android:layout_height="48dp"
      android:layout_weight="1"
      android:layout_margin="8dp"/>

  </LinearLayout>

</LinearLayout>