1、Cannot resolve symbol 'AppCompatActivity'
依赖时依赖库不对
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'androidx.appcompat:appcompat:1.1.0-alpha03'
2、gradle的阿里地址：
maven { url 'https://maven.aliyun.com/repository/public' }
maven { url 'https://maven.aliyun.com/repository/central' }
maven { url 'https://maven.aliyun.com/repository/google' }
maven { url 'https://maven.aliyun.com/repository/public' }
maven { url 'https://maven.aliyun.com/repository/gradle-plugin' }