如果您之前学习 Android MVP ，很可能是从 AndroidMVPSample(https://github.com/WuXiaolong/AndroidMVPSample)开始的，此Sample最初是 Android MVP 示例，后来融合 Retrofit 和 RxJava，分别演示了普通写法(Retrofit)、普通写法(Retrofit+Rxjava)、MVP+Retrofit+Rxjava，跟它一样，我写了 Kotlin 版 Retrofit +RxJava 来练手，还是以天气示例。

依赖

build.gradle

buildscript {
    ext.kotlin_version = '1.1.2-4'
    ext.retrofit_version = '2.0.2'
    ext.rxkotlin_version = '0.60.0'
    ext.rxandroid_version = '1.2.1'

    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.1'
        //编译 Kotlin 源代码和模块.
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }}

app/build.gradle

 apply plugin: 'com.android.application'apply plugin: 'kotlin-android'android {
    //……}dependencies {
    
    //针对 JDK 7 或 JDK 8
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    
    //Retrofit
    compile "com.squareup.retrofit2:retrofit:$retrofit_version"
    compile "com.squareup.okhttp3:logging-interceptor:$logging_interceptor_version"
    compile "com.squareup.retrofit2:converter-gson:$retrofit_version"
    compile "com.squareup.retrofit2:adapter-rxjava:$retrofit_version"
   
    //RxJava
    compile "io.reactivex:rxkotlin:$rxkotlin_version"
    compile "io.reactivex:rxandroid:$rxandroid_version"}

网络权限

AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />

WeatherinfoModel

天气接口：http://www.weather.com.cn/adat/sk/101190201.html当我们使用 Gson 来解析 json 到我们的类中，这些属性的名字必须要与json中的名字一样，哎，我又忘记这点，因此浪费了很多时间排错。

data class WeatherinfoModel constructor(val weatherinfo: WeatherinfoBean) {

    data class WeatherinfoBean(
            val city: String,
            val cityid: String
    )}

ApiStores

网络请求 url 都放这里:

interface ApiStores {
    companion object {
        //baseUrl
        val API_SERVER_URL = "http://www.weather.com.cn/"
    }

    //加载天气
    @GET("adat/sk/{cityId}.html")
    fun loadData(@Path("cityId") cityId: String): Observable<WeatherinfoModel>}

ApiClient

Retrofit 初始化、配置：

//object声明单例模式
object ApiClient {
    fun retrofit(): ApiStores {
        val builder = OkHttpClient.Builder()

        if (BuildConfig.DEBUG) {
            // Log信息拦截器
            val loggingInterceptor = HttpLoggingInterceptor()
            loggingInterceptor.level = HttpLoggingInterceptor.Level.BODY
            //设置 Debug Log 模式
            builder.addInterceptor(loggingInterceptor)
        }
        val okHttpClient = builder.build()
        val retrofit = Retrofit.Builder()
                .baseUrl(ApiStores.API_SERVER_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .client(okHttpClient)
                .build()
        //ApiStores::class.java取得对象的 Java 类
        return retrofit.create(ApiStores::class.java)
    }}

ApiCallback

还是做了回调：

abstract class ApiCallback<M> : Subscriber<M>() {
    abstract fun onSuccess(model: M)
    abstract fun onFailure(msg: String?)
    abstract fun onFinish()

    override fun onCompleted() {
        onFinish()
    }

    override fun onNext(m: M) {
        onSuccess(m)
    }

    override fun onError(e: Throwable?) {
        //这块应该可以优化 
        if (e is HttpException) {
            val httpException = e
            //httpException.response().errorBody().string()
            val code = httpException.code()
            var msg = httpException.message
            Log.d("wxl", "code=" + code)
            if (code == 504) {
                msg = "网络不给力"
            }
            if (code == 502 || code == 404) {
                msg = "服务器异常，请稍后再试"
            }
            onFailure(msg)
        } else {
            onFailure(e.toString())
        }
        onFinish()
    }}

BaseActivity

建了基类，可以把一些公用的方法放到这里，方便：

open class BaseActivity : AppCompatActivity() {
    val mCompositeSubscription: CompositeSubscription = CompositeSubscription()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }

    override fun onDestroy() {
        if (mCompositeSubscription.hasSubscriptions()) {
            //取消注册，以避免内存泄露
            mCompositeSubscription.unsubscribe()
        }
        super.onDestroy()
    }

    open fun <M> addSubscription(observable: Observable<M>, subscriber: Subscriber<M>) {
        mCompositeSubscription.add(
                observable.subscribeOn(Schedulers.io())
                        .observeOn(AndroidSchedulers.mainThread())
                        .subscribe(subscriber))
    }}

MainActivity

请求接口：

//冒号表示继承
class MainActivity : BaseActivity() {
    //问号表示该变量可以为空
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //object为对象表达式
        addSubscription(ApiClient.retrofit().loadData("101190201"), object : ApiCallback<WeatherinfoModel>() {
            override fun onSuccess(model: WeatherinfoModel) {
                Log.d("wxl", "city=" + model.weatherinfo.city + ",cityid=" + model.weatherinfo.cityid)//输出“city=无锡,cityid=101190201”
            }

            override fun onFailure(msg: String?) {
                Log.d("wxl", "onFailure=" + msg)
            }

            override fun onFinish() {
                Log.d("wxl", "onFinish")
            }
        })
    }}

参考

Keddit — Part 6: API — Retrofit & Kotlin

Kotlin for Android 实践

系列博客

Kotlin for Android（一）准备工作

Kotlin for Android（二）基础语法

Kotlin for Android（三）类和对象