build.gradle（module）

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28   //对应sdk版本
    buildToolsVersion "28.0.3"  //对应工具

    defaultConfig {
        applicationId "com.example.myfirstapp"  //包名
        minSdkVersion 21   //最小sdk
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {   //release 版本
            minifyEnabled false //打包apk是否优化，体积缩小
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies { //依赖
    compile fileTree(dir: 'libs', include: ['*.jar'])
    //compile  “Group” “name” "version"
}