Android Studio 报错：Could not find com.android.support:appcompat-v7:28.0.0-beta01.

报错内容如下，

Could not find com.android.support:appcompat-v7:28.0.0-beta01.
Searched in the following locations:
file:/D:/AndroidSDK/extras/m2repository/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.pom
file:/D:/AndroidSDK/extras/m2repository/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.jar
file:/D:/AndroidSDK/extras/google/m2repository/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.pom
file:/D:/AndroidSDK/extras/google/m2repository/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.jar
file:/D:/AndroidSDK/extras/android/m2repository/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.pom
file:/D:/AndroidSDK/extras/android/m2repository/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.jar
https://jcenter.bintray.com/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.pom
https://jcenter.bintray.com/com/android/support/appcompat-v7/28.0.0-beta01/appcompat-v7-28.0.0-beta01.jar
Required by:
project :app

Please install the Android Support Repository from the Android SDK Manager.
Open Android SDK Manager

首先想到的是换版本，在app->build.gradle中进行各种尝试，如

implementation 'com.android.support:appcompat-v7:27.1.1'

都不成功，最后把原来的项目拉出来，发现新项目project->build.gradle的repositories中都有google()，于是加上，问题解决。与app->build.gradle无关。

注意看全文，其中有两处必须都有google()，如下

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}