A prototype of a loading indicator utilizing repeated gradients. See https://twitter.com/crafty/status/914830571196571648

avd_loading_bar.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright 2017 Google Inc.

  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.
  -->

<animated-vector
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:aapt="http://schemas.android.com/aapt"
    android:drawable="@drawable/loading_bar">
    <target android:name="loading_bar">
        <aapt:attr name="android:animation">
            <!-- translate left by 2 stripes -->
            <objectAnimator
                android:propertyName="translateX"
                android:duration="700"
                android:interpolator="@android:interpolator/linear"
                android:valueFrom="0"
                android:valueTo="-64"
                android:repeatCount="-1" />
        </aapt:attr>
    </target>
</animated-vector>

loading_bar.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  Copyright 2017 Google Inc.

  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.
  -->

<vector
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:aapt="http://schemas.android.com/aapt"
    android:width="360dp"
    android:height="32dp"
    android:viewportWidth="360"
    android:viewportHeight="32">
    <clip-path android:pathData="M8,0L352,0A8,8 0,0 1,360 8L360,24A8,8 0,0 1,352 32L8,32A8,8 0,0 1,0 24L0,8A8,8 0,0 1,8 0z" />
    <group android:name="loading_bar">
        <!-- note: this shape draws beyond the right edge of the viewport as it will be animated leftward -->
        <path android:pathData="M0,0 L424,0 L424,32 L0,32 Z">
            <aapt:attr name="android:fillColor">
                <gradient
                    android:endX="32"
                    android:endY="32"
                    android:startX="0"
                    android:startY="0"
                    android:tileMode="repeat"
                    android:type="linear">
                    <item
                        android:color="#c12124"
                        android:offset="0.0" />
                    <item
                        android:color="#c12124"
                        android:offset="0.5" />
                    <item
                        android:color="#ffffff"
                        android:offset="0.5" />
                    <item
                        android:color="#ffffff"
                        android:offset="1.0" />
                </gradient>
            </aapt:attr>
        </path>
    </group>

    <!-- sheen -->
    <path
        android:fillAlpha=".2"
        android:fillColor="#FFF"
        android:pathData="M8,2L352,2A6,6 0,0 1,358 8L358,8A6,6 0,0 1,352 14L8,14A6,6 0,0 1,2 8L2,8A6,6 0,0 1,8 2z" />
</vector>