core/res/res/layout/notification_template_material_messaging.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  ~ Copyright (C) 2016 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
  -->
<com.android.internal.widget.MessagingLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/status_bar_latest_event_content"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:clipChildren="false"
    android:tag="messaging"
    >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:clipChildren="false"
        android:orientation="vertical"
        >


        <com.android.internal.widget.NotificationMaxHeightFrameLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:minHeight="@dimen/notification_min_height"
            android:clipChildren="false"
            >

            <ImageView
                android:id="@+id/left_icon"
                android:layout_width="@dimen/notification_left_icon_size"
                android:layout_height="@dimen/notification_left_icon_size"
                android:layout_gravity="center_vertical|start"
                android:layout_marginStart="@dimen/notification_left_icon_start"
                android:background="@drawable/notification_large_icon_outline"
                android:clipToOutline="true"
                android:importantForAccessibility="no"
                android:scaleType="centerCrop"
                android:visibility="gone"
                />

            <com.android.internal.widget.CachingIconView
                android:id="@+id/icon"
                android:layout_width="@dimen/notification_icon_circle_size"
                android:layout_height="@dimen/notification_icon_circle_size"
                android:layout_gravity="center_vertical|start"
                android:layout_marginStart="@dimen/notification_icon_circle_start"
                android:background="@drawable/notification_icon_circle"
                android:padding="@dimen/notification_icon_circle_padding"
                />

            <FrameLayout
                android:id="@+id/alternate_expand_target"
                android:layout_width="@dimen/notification_content_margin_start"
                android:layout_height="match_parent"
                android:layout_gravity="start"
                android:importantForAccessibility="no"
                />

            <!--
              NOTE: to make the expansion animation of id/notification_messaging happen vertically,
              its X positioning must be the left edge of the notification, so instead of putting the
              layout_marginStart on the id/notification_headerless_view_row, we put it on
              id/notification_top_line, making the layout here just a bit different from the base.
              -->
            <LinearLayout
                android:id="@+id/notification_headerless_view_row"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="horizontal"
                android:clipChildren="false"
                >

                <!--
                  NOTE: because messaging will always have 2 lines, this LinearLayout should NOT
                  have the id/notification_headerless_view_column, as that is used for modifying
                   vertical margins to accommodate the single-line state that base supports
                  -->
                <LinearLayout
                    android:layout_width="0px"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_vertical"
                    android:layout_weight="1"
                    android:layout_marginBottom="@dimen/notification_headerless_margin_twoline"
                    android:layout_marginTop="@dimen/notification_headerless_margin_twoline"
                    android:clipChildren="false"
                    android:orientation="vertical"
                    >

                    <NotificationTopLineView
                        android:id="@+id/notification_top_line"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:minHeight="@dimen/notification_headerless_line_height"
                        android:layout_marginStart="@dimen/notification_content_margin_start"
                        android:clipChildren="false"
                        android:theme="@style/Theme.DeviceDefault.Notification"
                        >

                        <!--
                        NOTE: The notification_top_line_views layout contains the app_name_text.
                        In order to include the title view at the beginning, the Notification.Builder
                        has logic to hide that view whenever this title view is to be visible.
                        -->

                        <TextView
                            android:id="@+id/title"
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_marginEnd="@dimen/notification_header_separating_margin"
                            android:ellipsize="end"
                            android:fadingEdge="horizontal"
                            android:singleLine="true"
                            android:textAlignment="viewStart"
                            android:textAppearance="@style/TextAppearance.DeviceDefault.Notification.Title"
                            />

                        <include layout="@layout/notification_top_line_views" />

                    </NotificationTopLineView>

                    <LinearLayout
                        android:id="@+id/notification_main_column"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:orientation="vertical"
                        android:clipChildren="false"
                        >
                        <com.android.internal.widget.MessagingLinearLayout
                            android:id="@+id/notification_messaging"
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:clipChildren="false"
                            android:spacing="@dimen/notification_messaging_spacing" />
                    </LinearLayout>

                </LinearLayout>

                <!-- Images -->
                <com.android.internal.widget.MessagingLinearLayout
                    android:id="@+id/conversation_image_message_container"
                    android:layout_width="@dimen/notification_right_icon_size"
                    android:layout_height="@dimen/notification_right_icon_size"
                    android:layout_gravity="center_vertical|end"
                    android:layout_marginTop="@dimen/notification_right_icon_headerless_margin"
                    android:layout_marginBottom="@dimen/notification_right_icon_headerless_margin"
                    android:layout_marginStart="@dimen/notification_right_icon_content_margin"
                    android:forceHasOverlappingRendering="false"
                    android:spacing="0dp"
                    android:clipChildren="false"
                    android:visibility="gone"
                    />

                <ImageView
                    android:id="@+id/right_icon"
                    android:layout_width="@dimen/notification_right_icon_size"
                    android:layout_height="@dimen/notification_right_icon_size"
                    android:layout_gravity="center_vertical|end"
                    android:layout_marginTop="@dimen/notification_right_icon_headerless_margin"
                    android:layout_marginBottom="@dimen/notification_right_icon_headerless_margin"
                    android:layout_marginStart="@dimen/notification_right_icon_content_margin"
                    android:background="@drawable/notification_large_icon_outline"
                    android:clipToOutline="true"
                    android:importantForAccessibility="no"
                    android:scaleType="centerCrop"
                    />

                <FrameLayout
                    android:id="@+id/expand_button_touch_container"
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:minWidth="@dimen/notification_content_margin_end"
                    >

                    <include layout="@layout/notification_expand_button"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_gravity="center_vertical|end"
                        />

                </FrameLayout>

            </LinearLayout>

        </com.android.internal.widget.NotificationMaxHeightFrameLayout>

    <LinearLayout
            android:id="@+id/notification_action_list_margin_target"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="-20dp"
            android:clipChildren="false"
            android:orientation="vertical">
        <include layout="@layout/notification_template_smart_reply_container"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="@dimen/notification_content_margin"
                android:layout_marginStart="@dimen/notification_content_margin_start"
                android:layout_marginEnd="@dimen/notification_content_margin_end" />
        <include layout="@layout/notification_material_action_list" />
    </LinearLayout>
</LinearLayout>
</com.android.internal.widget.MessagingLayout>