Android开发-kotlin基本使用(一)

1、RecyclerView列表布局

在item_view_linear_vertical.xml中:

在fragment_study.xml中:

在ui-->study-->StudyFragment中:

package com.dbc.bckotlinall.ui.study

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.dbc.bckotlinall.R
import kotlinx.android.synthetic.main.fragment_study.*
import kotlinx.android.synthetic.main.item_view_linear_vertical.view.*


class StudyFragment: Fragment(R.layout.fragment_study) {//关联布局
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        // 需要先安装扩展插件, 就可以直接通过id名访问控件了
        recycler_view.layoutManager = LinearLayoutManager(context,LinearLayoutManager.VERTICAL,false)
        recycler_view.adapter = StudyAdapter()
    }

    // inner 用于声明StudyAdapter是StudyFragment的内部类
    inner class StudyAdapter : RecyclerView.Adapter() {
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
            val itemView = LayoutInflater.from(context).inflate(R.layout.item_view_linear_vertical, parent, false)
            return StudyViewHolder(itemView)
        }

        override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
          
            /// 在代码中给image控件设置图片的三种方式:
            holder.itemView.item_image.setImageResource(R.drawable.ic_dashboard_black_24dp)//✅
            holder.itemView.item_image.setImageDrawable(
              ContextCompat.getDrawable(
                context!!,// !!表示说明此对象不为空
                R.drawable.icon_jetpack
              )
            )
            holder.itemView.item_image.setImageBitmap(BitmapFactory.decodeResource(context!!.resource, R.drawable.icon_jetpack))
          
            holder.itemView.item_title.text="标题$position"
            holder.itemView.item_message.text="内容${position} 能接收到分离焦虑世纪东方垃圾水电费拉伸点击分类计数法  打开了施法距离卡机士大夫撒的发生撒旦法阿斯顿发安达市 发"
        }

        override fun getItemCount(): Int {
            return 20
        }

        inner class StudyViewHolder(view: View):RecyclerView.ViewHolder(view){

        }

    }
}

2、GradLayoutManager网格布局

class HomeFragment : Fragment(R.layout.fragment_home){
  override fun onViewCreated(view: View, savedInstanceState: Bundle?){
    super.onViewCreated(View, savedInstanceState)
    
    recycler_view.layoutManager = LinearLayoutManager(context, 3)//3表示3列
    
    recycler_view.adapter = MyAdapter()
  }
  
  // inner: 声明MyAdapter为HomeFragment的内部类
  inner class MyAdapter: RecyclerView.Adapter(){
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyVIewHolder{
      //访问外部类的context对象
      val itemView = LayoutInflater.from(context)
        .inflate(R.layout.item_view_grid, parent, false)
      return MyViewHolder(itemView)
    }
    
    // 告诉列表有多少条数据
    override fun getItemCount(): Int{
      return 20
    }
    
    //数据绑定
    override fun onBindViewHolder(holder: MyViewHolder, position: Int){
      /// 在代码中给image控件设置图片的三种方式:
      holder.itemView.item_image.setImageResource(R.drawable.icon_jetpack)//✅
      holder.itemView.item_image.setImageDrawable(
        ContextCompat.getDrawable(
          context!!,// !!表示说明此对象不为空
          R.drawable.icon_jetpack
        )
      )
      holder.itemView.item_image.setImageBitmap(BitmapFactory.decodeResource(context!!.resource, R.drawable.icon_jetpack))
    }
  }
  
  class MyViewHolder(view: View): RecyclerView.ViewHolder(view){
    
  }
}

3、StaggeredGridLayoutManager瀑布流

recycleView.adapter = MyAdapter()

class HomeFragment : Fragment(R.layout.fragment_home){
  override fun onViewCreated(view: View, savedInstanceState: Bundle?){
    super.onViewCreated(View, savedInstanceState)
    
    recycler_view.layoutManager = StaggeredGridLayoutMananger(2, StaggeredGridLayoutMananger.VERTICAL)//2表示2列, VERTICAL表示纵向瀑布流
    
    recycler_view.adapter = MyAdapter()
  }
  
  // inner: 声明MyAdapter为HomeFragment的内部类
  inner class MyAdapter: RecyclerView.Adapter(){
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyVIewHolder{
      //访问外部类的context对象
      val itemView = LayoutInflater.from(context)
        .inflate(R.layout.item_view_grid, parent, false)
      return MyViewHolder(itemView)
    }
    
    // 告诉列表有多少条数据
    override fun getItemCount(): Int{
      return 20
    }
    
    //数据绑定
    override fun onBindViewHolder(holder: MyViewHolder, position: Int){
      /// 在代码中给image控件设置图片的三种方式:
      holder.itemView.item_image.setImageResource(R.drawable.icon_jetpack)//✅
      if(position == 0||position == 3||position == 4||position == 7||position == 9){
        holder.itemView.item_message.setSingleLine(false)//取消设置单行显示
      } else {
        holder.itemView.item_message.setSingleLine(true)//单行显示
      }
      holder.itemView.item_message.text = "xxxxx"
    }
  }
  
  class MyViewHolder(view: View): RecyclerView.ViewHolder(view){
    
  }
}

4、快速实现圆角阴影的组件

// 这一行代码, 放在顶部layout标签中声明
xmlns:app="http://schemas.android.com/apk/res-auto"


    
        
        ...
               

AndroidStudio配置阿里云镜像  2021.02.25 10:46 2020浏览
https://www.imooc.com/article/315290


Mac IDEA配置阿里云国内镜像 发布于 2020-07-30
https://segmentfault.com/a/1190000023086534


警告:You have JVM property “https.proxyHost“ set to “127.0.0.1“
https://www.jianshu.com/p/9cec82d9498e

5、网络请求框架OKHTTP--GET请求

在app->manifests->AndroidManifest.xml添加网络访问权限:

在app/build.gradle的dependencies中添加下面的依赖

dependencies {
  ...
  implementation("com.squareup.okhttp3:okhttp:4.9.0")
  // 网络请求日志打印
  implementation("com.squareup.okhttp3:logging-interceptor:4.9.0")
}

在http->HiOkHttp中

package com.dbc.bckotlinall.http

import android.util.Log
import okhttp3.Call
import okhttp3.OkHttpClient
import okhttp3.Request
import java.util.concurrent.TimeUnit

// 使用class需要创建实例对象
// 使用object的声明方式, 就没有必要构建它的实例对象了, 直接可以类.方法调用
object HiOkHttp {
    private val BASE_URL="http://123.56.232.18:8080/serverdemo"
    //全局中只有一份
    val client  = OkHttpClient.Builder()    //builder构造者设计模式
        .connectTimeout(10, TimeUnit.SECONDS) //连接超时时间
        .readTimeout(10, TimeUnit.SECONDS)    //读取超时
        .writeTimeout(10, TimeUnit.SECONDS)  //写超时，也就是请求超时
        .build();

    // Android分为主线程和子线程
    // 主线程就是APP一启动后, Android framework层会启动一个线程, 主线程(UI线程)
    // 子线程 -- 可以通过new Thread().start()创建

    //方式一: 同步GET请求
    fun get(url: String) {//网络请求接口
        Thread(Runnable {//开启子线程
            //构造请求体
            val request: Request = Request.Builder()
//                .url(url)
                .url("$BASE_URL/user/query?userId=1600932269")
                .build()
            //构造请求对象
            val call: Call = client.newCall(request)
            // 通过.execute()发起同步请求--同步执行
            val response = call.execute()
            val body = response.body?.string()
//            println("get response :${body}")
            Log.e("OKHTTP","get response :${body}")
        }).start()
    }
  
  //方式二: 异步GET请求
  fun getAsync(url: String) {//网络请求接口
        //构造请求体
        val request: Request = Request.Builder()
//                .url(url)
            .url("$BASE_URL/user/query?userId=1600932269")
            .build()
        //构造请求对象
        val call: Call = client.newCall(request)
        // 通过.enqueue()发起异步请求--异步执行
        call.enqueue(object: Callback {//异步请求没有返回值
            override fun onFailure(call: Call, e: IOException) {
                Log.e("OKHTTP","失败原因 :${e}")
            }

            override fun onResponse(call: Call, response: Response) {
                val body = response.body?.string()
                Log.e("OKHTTP","get response :${body}")
            }
        })
    }
}

在MainActivity.kt中使用:

HiOkHttp.get()

6、网络请求框架OKHTTP--POST请求

http://123.56.232.18:8080/serverdemo/swagger-ui.html#/tag-list-controller/toggleTagFollowUsingPOST

/// 同步表达提交
fun post(){
    val body = FormBody.Builder()
        .add("userId","1600932269")
        .add("tagId","71")
        .build()
    val request = Request.Builder().url("$BASE_URL/tag/toggleTagFollow")
        .post(body)
        .build()
    val call = client.newCall(request)
    Thread(Runnable {
        val response = call.execute()
        Log.e("OKHTTP","post response: ${response.body?.string()}")
    }).start()
}

/// 异步表单提交
fun postAsync(){
    val body = FormBody.Builder()
        .add("userId","1600932269")
        .add("tagId","71")
        .build()
    val request = Request.Builder().url("$BASE_URL/tag/toggleTagFollow")
        .post(body)
        .build()
    val call = client.newCall(request)
    call.enqueue(object :Callback{
        override fun onFailure(call: Call, e: IOException) {
            Log.e("OKHTTP","失败原因 :${e}")
        }

        override fun onResponse(call: Call, response: Response) {
            val body = response.body?.string()
            Log.e("OKHTTP","post response :${body}")
        }
    })
}

/// 异步多表单文件上传, 在Android6.0以后, 读取外部存储卡文件都是需要动态申请权限的
fun postAsyncMultipart(context: Context) {

    val file = File(Environment.getExternalStorageDirectory(), "1.png")// 文件目录, 文件名称
    if (!file.exists()) {
        Toast.makeText(context, "文件不存在", Toast.LENGTH_SHORT).show()
        return
    }
    val body = MultipartBody.Builder()
        .addFormDataPart("key","value")
        .addFormDataPart("key1","value1")
        .addFormDataPart(
            "file",
            "1.png",
            RequestBody.create("application/octet-stream".toMediaType(), file)
        )
        .build()

    val request = Request.Builder().url("接口是需要支持文件上传才可以使用的")
        .post(body)
        .build()

    val  call = client.newCall(request)
    call.enqueue( object : Callback{
        override fun onFailure(call: Call, e: IOException) {
            Log.e("OKHTTP","失败原因 :${e}")
        }

        override fun onResponse(call: Call, response: Response) {
            val body = response.body?.string()
            Log.e("OKHTTP","postAsyncMultipart response :${body}")
        }
    })
}

/// 异步POST请求---提交字符串
fun postString(){
    ///可以是JSON字符串, 也可以是纯文本字符串

    //纯文本
//        val textPlain = "text/plain;charset=utf-8".toMediaType()
//        val textObj = "{username:admin, password:admin}"
//        val body = RequestBody.create(textPlain,textObj)

    //Json字符串
    val jsonObj = JSONObject()
    jsonObj.put("key1","value1")
    jsonObj.put("key2",100)
    val applicationJson = "application/json;charset=utf-8".toMediaType()

    val body = RequestBody.create(applicationJson,jsonObj.toString())

    val request = Request.Builder().url("$BASE_URL")
        .post(body)
        .build()

    val  call = client.newCall(request)
    call.enqueue( object : Callback{
        override fun onFailure(call: Call, e: IOException) {
            Log.e("OKHTTP","失败原因 :${e}")
        }

        override fun onResponse(call: Call, response: Response) {
            val body = response.body?.string()
            Log.e("OKHTTP","postString response :${body}")
        }
    })
}

7、拦截器LoggingInterceptor

使用OkHttp默认拦截器

object HiOkHttp {
    private val BASE_URL="http://123.56.232.18:8080/serverdemo"
    private  val client: OkHttpClient 

    init {
        val httpLoggingInterceptor = HttpLoggingInterceptor()
        httpLoggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY)
        client  = OkHttpClient.Builder()    //builder构造者设计模式
            .connectTimeout(10, TimeUnit.SECONDS) //连接超时时间
            .readTimeout(10, TimeUnit.SECONDS)    //读取超时
            .writeTimeout(10, TimeUnit.SECONDS)  //写超时，也就是请求超时
            .addInterceptor(httpLoggingInterceptor)//使用默认拦截器
            .build();
    }
    ....
}

使用自定义拦截器:

/// ①在LoggingInterceptor.kt中:

package com.dbc.bckotlinall.http

import android.util.Log
import okhttp3.Interceptor
import okhttp3.Response
import okhttp3.ResponseBody
import okio.Buffer

/// 拦截器要做的事: 打印拦截请求时的接口、携带哪些参数
class LoggingInterceptor: Interceptor {
    override fun intercept(chain: Interceptor.Chain): Response {
        val time_start = System.nanoTime()
        val request = chain.request() //获取request对象
        val response = chain.proceed(request)//获取response对象

        val buffer = Buffer()
        request.body?.writeTo(buffer)
        val requestBodyStr = buffer.readUtf8()//把request.body转换成字符串
        //打印请求前的: 地址 和 请求参数
        Log.e("OKHTTP",String.format("Sending request %s with params %s",request.url, requestBodyStr))

        val bussinessData = response.body?.string()?:"response body null" //读取输出流,获取接口返回的数据
        /*由于OKHTTP的工作原理: 一旦调用了response.body?.string()方法, 今后再也不能用response去读取它的响应流了.
        *
        * 这也就意味着: onResponse回调函数中,再次读取response.body?.string()就会报错. 这是OKHTTP的工作原理决定的.
        *
        * 对于Response响应流只能读取一次的解决办法是: 返回一个新的Response.
        * */
        val mediaType = response.body?.contentType()
        val newBody = ResponseBody.create(mediaType, bussinessData)
        val newResponse = response.newBuilder().body(newBody).build()

        val time_end = System.nanoTime()
        //打印请求后的结果
        Log.e("OKHTTP", String.format("Received response for %s in %.1fms >>> %s", request.url,(time_end-time_start)/1e6,bussinessData))

        return newResponse
    }
}

///②在HiOkHttp中使用:
object HiOkHttp {
    private val BASE_URL="http://123.56.232.18:8080/serverdemo"

    val client  = OkHttpClient.Builder()
        .connectTimeout(10, TimeUnit.SECONDS)
        .readTimeout(10, TimeUnit.SECONDS)
        .writeTimeout(10, TimeUnit.SECONDS)  
        .addInterceptor(LoggingInterceptor()) //添加自定义拦截器
        .build();
    ...
}

8、使用Gson来解析网络请求响应

在app/build.gradle中添加以下依赖配置

dependencies {
  implementation 'com.google.code.gson:gson:2.8.6'
}

在Account.kt中使用:

package com.dbc.bckotlinall.ui.study

import com.google.gson.Gson
import com.google.gson.reflect.TypeToken

fun main() {

    /// 把JSON转换成对象
    val json ="{\"uid\":\"00001\",\"userName\":\"Freeman\",\"telNumber\":\"13000000000\"}"
    val gson = Gson()//构建gson对象
    // 在kotlin中传入class类型, 需要xxx::class.java 格式
    val account:Account = gson.fromJson(json, Account::class.java)
    println("fromJson: ${account.toString()}")

    /// 把对象转换成JSON
    val accountJson = gson.toJson(account)
    println("toJson: ${accountJson}")

    /// 将JSON转换成集合
    val jsonList= "[{\"uid\":\"00001\",\"userName\":\"Freeman\",\"telNumber\":\"13000000000\"}]"
    val accountList: List = gson.fromJson(jsonList, object:TypeToken>(){}.type)
    println("fromJson to List:${accountList.size}")

    /// 将集合转化成JSON
    val accountJsonList = gson.toJson(accountList)
    println("list to json: ${accountJsonList}")
}

class Account {
    /// 在kotlin中必须指定初始值
    var uid:String=""
    var userName:String=""
    var password:String=""
    var telNumber:String=""

    //✅快速生成toString: 首先选中这几个字段-->右键"Generate"-->选择"toString()"-->全选
    override fun toString(): String {
        return "Account(uid='$uid', userName='$userName', password='$password', telNumber='$telNumber')"
    }
}

如果对象模型使用data class, 就可以不用指定初始值了:

data class Account(
    var uid:String = "111",
    var userName:String,
    var password:String,
    var telNumber:String
)

使用插件快速生成复杂的数据模型 -- JsonToKotlin插件:

sp1.在网站 https://github.com/wuseal/JsonToKotlinClass/releases/  下载最新版本zip包
sp2.在AS-->Preferences-->Plugins-->点击"设置"按钮, 选择"install Plugin from Disk..."--->选择下载的包,点击"OK", 重启IDE

使用插件:
在空白的地方, 右键选择"Generate"-->选择"Kotlin data classes from JSON"-->将JSON字符串拷贝到这里-->点击"Format", 输入"Class Name: xxx", 选择"Generate" --> 就生成了xxx对象模型

val userModelJson = "{ ... }"
val userResponse:UserResponse! =  gson.fromJson(userModelJson, UserResponse::class.java)
println("userResponse: $userResponse")

9、RESTFUL网络请求框架Retrofit

retrofit注解驱动型上层网络请求框架, 使用注解来简化请求, 大体分为以下几类:

• 用于标注网络请求的注解
• 标记网络请求参数的注解
• 用于标记网络请求和响应格式的注解

添加依赖:

implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0' //json转换

在HiRetrofit.kt中, 封装Retrofit&定义接口:

package com.dbc.bckotlinall.http

import okhttp3.OkHttpClient
import retrofit2.Call
import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.http.GET
import retrofit2.http.Query
import java.util.concurrent.TimeUnit

object HiRetrofit {

    // https://www.cnblogs.com/hanma/p/14942740.html

    private val client  = OkHttpClient.Builder()    //builder构造者设计模式
        .connectTimeout(10, TimeUnit.SECONDS) //连接超时时间
        .readTimeout(10, TimeUnit.SECONDS)    //读取超时
        .writeTimeout(10, TimeUnit.SECONDS)  //写超时，也就是请求超时
        .addInterceptor(LoggingInterceptor())
        .build();

    private val retrofit = Retrofit.Builder()
        .client(client)//配置OKHTTP网络请求的一个对象
        .baseUrl("http://123.56.232.18:8080/serverdemo/")//配置网络请求的域名
        .addConverterFactory(GsonConverterFactory.create())//数据转换器: 自动转换成数据模型
        .build();

    ///定义一个泛型方法
    fun  create(clazz: Class): T {
        return retrofit.create(clazz)
    }
}

/// 定义一个接口文件, 编写网络请求方法
interface APIService{
    @GET(value="user/query")
    fun queryUser(@Query(value="userId",encoded = true) userId: String):Call
  //UserResponse: 要转换的数据模型对象类
}

在MainActivity.kt中使用:

val apiService = HiRetrofit.create(APIService::class.java)
// 此时onFailure 和 onResponse的回调都是在主线程的; 但OKHTTP的回调是在子线程的,如果UI操作还需要回到主线程.
apiService.queryUser("1600932269").enqueue(object: Callback{
    override fun onFailure(call: Call, t: Throwable) {
        Log.e("Retrofit","失败原因 :${t.message}")
    }

    override fun onResponse(call: Call, response: Response) {
        val body = response.body?.string()
        Log.e("Retrofit","get response :${body}")
    }
})

10、网络图片的加载

在app/build.gradle中添加以下配置。使用Glide加载图片

plugins {
    ...
    id 'kotlin-kapt'
}

dependencies {
    ...
    implementation 'com.github.bumptech.glide:glide:4.9.0'
    kapt 'com.github.bumptech.glide:compiler:4.9.0'
}

11、数据请求与绑定

class StudyFragment: Fragment(R.layout.fragment_study) {//关联布局
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val adapter = StudyAdapter()
        recycler_view.layoutManager = LinearLayoutManager(context,LinearLayoutManager.VERTICAL,false)
        recycler_view.adapter = adapter
      
        HiRetrofit.create(ApiService::class.java)
            .getStudy().enqueue(object: CallBack>{
            override fun onFailure(call: Call>, t: Throwable){
                Log.e("onFailure:", t.message ?: "unknown error")
            }

            override fun onResponse(
                call: Call>,
                response: Response>
            ){
                Log.e("onResponse:", response.body()?.toString() ?: "unknown error")
                response.body()?.let{
                    adapter.setDatas(it)//更新UI
                }
            }
        })
    }
  

    inner class StudyAdapter : RecyclerView.Adapter() {

        private  val  courses = mutableListOf()
        fun setDatas(datas: List) {
            if (datas.isNotEmpty()){
                courses.addAll(datas)
                notifyDataSetChanged() //这个命令会重新执行getItemCount和onBindViewHolder
            }
        }

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
            val itemView = LayoutInflater.from(context).inflate(R.layout.item_view_linear_vertical, parent, false)
            return StudyViewHolder(itemView)
        }

        // 重写执行这里才会刷新
        override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
            val course = courses[position]
//            holder.itemView.item_image.setImageResource(R.drawable.ic_dashboard_black_24dp)//本地图片
          
            //设置圆角
            val options = RequestOptions()
                .transform(RoundedCorners(10))//设置圆角
                        //添加网络图片
            Glide.with(context!!)
                .load(course.poster)//设置图片地址
                    .apply ( options )
                .into(holder.itemView.item_course_poster)//绑定控件
            holder.itemView.item_title.text = course.title
            holder.itemView.item_message.text="内容${position} "
        }

        override fun getItemCount(): Int {
            return courses.size
        }

        inner class StudyViewHolder(view: View):RecyclerView.ViewHolder(view){

        }
    }
}

12、列表的增删改查

class StudyFragment: Fragment(R.layout.fragment_study) {//关联布局
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val adapter = StudyAdapter()
        recycler_view.layoutManager = LinearLayoutManager(context,LinearLayoutManager.VERTICAL,false)
        recycler_view.adapter = adapter

        //点击增加按钮
        tab_add_course.setOnClickListener{
            val course = Course(
                label = "Android学习基础",
                poster = "https://www.songyubao.com/static/book/assets/icon-android.jpeg",
                progress = "100%",
                title = "Android RecyclerView基础学习"
            )
            adapter.addCourse(course)
            recycler_view.scrollToPosition(0)//滑动到第0个位置
        }
          //点击删除按钮
        tab_delete_course.setOnClickListener{
            adapter.deleteCourse(0)
        }
        //点击更新按钮
        tab_update_course.setOnClickListener{
            adapter.updateCourse(0, "80%")
        }
      ...
    }

    inner class StudyAdapter : RecyclerView.Adapter() {

        private  val  courses = mutableListOf()
        fun setDatas(datas: List) {
            if (datas.isNotEmpty()){
                courses.addAll(datas)
                notifyDataSetChanged() //这个命令会重新执行getItemCount和onBindViewHolder
            }
        }

        fun addCourse(course: Course){
//            courses.add(0, course)
//            notifyItemChanged(0)

            courses.add(course)
            //notifyDataSetChanged()//更新整个列表
            notifyItemChanged(courses.size - 1)
        }

        fun deleteCourse(position: Int){
            courses.removeAt(position)
            //notifyDataSetChanged()//更新整个列表
            notifyItemRemoved(position)
        }

        fun updateCourse(position: Int, progress:String){
            val course = courses[position]
            course.progress = progress
            //notifyDataSetChanged()//更新整个列表
            notifyItemChanged(position)
        }
      ...

AS操作小技巧

1. 查看Kotlin编译之后的字节码, 有助于我们深入理解kotlin语言, 有两种方式:
   • Shift键两次, 输入Show kotlin
   • Tools->Kotlin->Show Kotlin Bytecode