一、方式一

android{
    repositories {
        flatDir {
            dirs 'libs'
        }
    }
}
dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation (name: 'barcode_scanner_library_v2.3.2.0', ext: 'aar')
}

二、方式二

android{
   //不用写
   /* repositories {
        flatDir {
            dirs 'libs'
        }
    }*/
}
dependencies {
　    将
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     改为
     implementation fileTree(dir: 'libs', include: ['*.jar','*.aar'])
}