car_product/car_ui_portrait/apps/CarUiPortraitSystemUI/res/drawable/nav_bar_button_background.xml

<!--
  ~ Copyright (C) 2021 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.
  -->
<selector xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:aapt="http://schemas.android.com/aapt">
    <item android:state_selected="true">
        <layer-list>
            <item>
                <ripple android:color="@color/car_ui_ripple_color">
                    <item>
                        <shape android:shape="rectangle">
                            <size android:width="@dimen/system_bar_button_size"
                                  android:height="@dimen/system_bar_button_size"/>
                            <corners
                                android:radius="@dimen/system_bar_button_corner_radius"/>
                            <solid
                                android:color="?android:attr/colorAccent"/>
                        </shape>
                    </item>
                </ripple>
            </item>
            <item android:drawable="@drawable/ic_minimize"
                  android:gravity="center"/>
        </layer-list>
    </item>
    <item>
        <layer-list>
            <item>
                <ripple android:color="@color/car_ui_ripple_color">
                    <item>
                        <shape android:shape="rectangle">
                            <size android:width="@dimen/system_bar_button_size"
                                  android:height="@dimen/system_bar_button_size"/>
                            <corners
                                android:radius="@dimen/system_bar_button_corner_radius"/>
                            <solid
                                android:color="@color/car_nav_icon_background_color"/>
                        </shape>
                    </item>
                </ripple>
            </item>
        </layer-list>
    </item>
</selector>