core/res/res/anim/dream_activity_open_enter.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
/* Copyright 2020, 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.
*/
-->

<!-- During this animation we keep the previous activity on the screen
using a noop animation for it (dream_activity_open_exit). The duration of
those two has to be the same. -->
<alpha xmlns:android="http://schemas.android.com/apk/res/android"
    android:fromAlpha="0.0"
    android:toAlpha="1.0"
    android:duration="@integer/config_dreamOpenAnimationDuration" />