1.第一步先在工程目录的build.gradle 添加这两行

buildscript {
    ext {
        kotlin_version = '1.5.21'
    }
  
    dependencies {
     
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

2.第二步在build.gradle(app)

头部加入 

apply plugin: 'kotlin-android'

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version" 
}