res/layout/conversation_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
    Copyright (C) 2015 The Android Open Source Project

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

         http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
-->
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:weightSum="1.0">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:orientation="vertical">
        <!-- This FrameLayout will take all available height (excluding media picker)
        but setting height to 0dp causes it not to shrink properly in KK, so a height of match_parent
        works equally well -->
        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1" >
            <!-- Message list -->
            <androidx.recyclerview.widget.RecyclerView
                android:id="@android:id/list"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:listSelector="@android:color/transparent"
                android:paddingTop="@dimen/action_bar_height"
                android:clipToPadding="false" />

            <View
                android:id="@+id/conversation_compose_divider"
                android:layout_width="match_parent"
                android:layout_height="4dp"
                android:layout_gravity="bottom"
                android:background="@drawable/conversation_compose_divider_gradient"
                android:alpha="0"
                android:importantForAccessibility="no" />

            <include layout="@layout/sim_selector_view"
                android:id="@+id/sim_selector"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:visibility="gone" />
        </FrameLayout>

        <!-- Attachments to send, compose message view, media picker. -->
        <include layout="@layout/compose_message_view"
            android:id="@+id/message_compose_view_container"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>

</LinearLayout>