效果展示

方式一直接新建新项目

AS3.1已经自带Kotlin插件，不需要额外安装

方式二 module中添加kotlin支持

project build.gradle

buildscript {
    ext.kotlin_version = '1.3.11'
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.4'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

module build.gradle

apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
android {
}

dependencies {
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
}

Activity

class TestActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        tvshow.text = "hello-kotlin"
    }
}

Activity-xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tvshow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>