安卓开发学习---kotlin版---笔记（三）

网络

安卓主页的网络框架：OkHttp
在OkHttp的基础上进行封装的：Retrofit框架，更常使用

OkHttp学习

在使用网络请求的时候，先添加网络访问权限：
<uses-permission android:name="android.permission.INTERNET" />

类似还有其他：

    <!--网络权限-->
    <uses-permission android:name="android.permission.INTERNET" />
    <!--写文件权限-->
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <!--读文件权限-->
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

除此之外，还有添加两个依赖：
在app-build.gradle-dependencies下：

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")

在高版本下，需要满足HTTPS的要求，如果你调试使用的是HTTP的接口，要加上：
android:usesCleartextTraffic="true"

没有请求的接口？

这个网站可以模拟接口请求：点我
或者
使用 天气预报

Get请求

同步请求

	private val BaseUrl = "http://www.tianqiapi.com"

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

    //get方法
    fun get(url: String){
        //创建一个子线程
        Thread(Runnable {
            val string2 = BaseUrl + url
            println("string2 = ${string2}")
            val request: Request = Request.Builder()//build构造者设计模式
                .url(string2)//请求地址
                .build()
            //client对象 与 request产生关联，返回一个Call对象
            val call: Call = client.newCall(request)
            //执行，返回一个Response对象(execute()是同步请求)
            val response: Response = call.execute()
            //获取body
            val body:String? = response.body?.string()


            //结果打印
            Log.e("OKHTTP", "get response body = ${body}")
            println("get response body = ${body}")
        }).start()
    }

异步请求

	///异步get请求
    fun getAsync(url: String){
        val string2 = BaseUrl + url
        println("string2 = ${string2}")
        val request: Request = Request.Builder()//build构造者设计模式
            .url(string2)//请求地址
            .build()
        //client对象 与 request产生关联，返回一个Call对象
        val call: Call = client.newCall(request)
        //执行，返回一个Response对象(enqueue()是异步请求)
        val response: Unit = call.enqueue(object :Callback{
            override fun onFailure(call: Call, e: IOException) {
                Log.e("OKHTTP", "get response body = ${e.message}")
                println("error = ${e.message}")
            }

            override fun onResponse(call: Call, response: Response) {
                //获取body
                val body:String? = response.body?.string()
                //结果打印
                Log.e("OKHTTP", "get response body = ${body}")
                println("get response body = ${body}")
            }
        })
    }

Post请求

同步请求

	//post方法
    fun post(url: String){
        //创建一个子线程
        Thread(Runnable {
            //创建body
            val body2 = FormBody.Builder()
                .add("key", "value")//添加参数
                .add("key2", "value2")
                .build()

            val string2 = BaseUrl + url
            println("string2 = ${string2}")
            val request: Request = Request.Builder()//build构造者设计模式
                .url(string2)//请求地址
                .post(body2)//接口参数
                .build()
            //client对象 与 request产生关联，返回一个Call对象
            val call: Call = client.newCall(request)
            //执行，返回一个Response对象(execute()是同步请求)
            val response: Response = call.execute()
            //获取body
            val body:String? = response.body?.string()
            //结果打印
            Log.e("OKHTTP", "get response body = ${body}")
            println("get response body = ${body}")
        }).start()
    } 

异步请求

	//post异步方法
    fun postAsync(url: String){
        //创建body
        val body2 = FormBody.Builder()
            .add("key", "value")//添加参数
            .add("key2", "value2")
            .build()

        val string2 = BaseUrl + url
        println("string2 = ${string2}")
        val request: Request = Request.Builder()//build构造者设计模式
            .url(string2)//请求地址
            .post(body2)//接口参数
            .build()
        //client对象 与 request产生关联，返回一个Call对象
        val call: Call = client.newCall(request)
        //执行，返回一个Response对象(enqueue()是同步请求)
        val response: Unit = call.enqueue(object :Callback{
            override fun onFailure(call: Call, e: IOException) {
                TODO("Not yet implemented")
            }
            override fun onResponse(call: Call, response: Response) {
                //获取body
                val body:String? = response.body?.string()
                //结果打印
                Log.e("OKHTTP", "get response body = ${body}")
                println("get response body = ${body}")
            }
        })
    }

拦截器

LoggingInterceptor

//继承Interceptor
class LoggingInterceptor : Interceptor{
    //重写方法
    override fun intercept(chain: Interceptor.Chain): Response {
        //获取当前请求的时间戳
        val time_start = System.nanoTime()
        //获取请求对象
        var request = chain.request()
        //获取响应对象
        var response = chain.proceed(request)

        //获取body
        var buffer = okio.Buffer()
        request.body?.writeTo(buffer)

        var requestBodyString = buffer.readUtf8()
        //打印
        Log.e("OKHTTP", String.format("request: %s, params: %s", request.url, requestBodyString))

        val businessData: String = response.body?.string() ?: "空"
        Log.e("OKHTTP", businessData);

        //此处需要创建新的response并返回，非直接返回
        return response
    }

}

GSON解析

首先，添加依赖：
implementation 'com.google.code.gson:gson:2.8.6'

JSON转model

import com.google.gson.Gson

fun main(){
    //json串
    val json ="{\"uid\":\"00001\",\"userName\":\"Freeman\",\"telNumber\":\"13000000000\"}";
    
    //创建一个gson对象
    var gson = Gson()
    //json转model
    val account = gson.fromJson<Account>(json, Account::class.java);

    //打印某一个账号的名字
    println(account.userName)
    //打印所有属性
    println(account.toString())
    
}


class Account{
    var uid: String = "001"
    var userName: String = "jack"
    var password: String = "123456"
    var telNumber: String = "130000000"
    override fun toString(): String {
        return "Account(uid='$uid', userName='$userName', password='$password', telNumber='$telNumber')"
    }
}

model转JSON

//model转Json
println("model转Json ${gson.toJson(account)}")

JsonToKotlin插件：可以将json转化为模型定义属性

---

Fragment

fragment不能单独使用，要嵌在activity里面
fragment的生命周期，受宿主（activity）的生命周期的影响

fragment的生命周期：

//Activity
class FragmentStudyActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_fragment_study)

        //创建fragment对象
        val fragment = FragmentStudy()
        //传递数据
        //创建一个bundle
        val bundle = Bundle()
        bundle.putInt("key1", 22)
        bundle.putString("key2", "wwwwwwww")
        //赋值
        fragment.arguments = bundle

        //并联关系
        val beginTransaction = supportFragmentManager.beginTransaction()
        //将某个layout的id拿到，添加到fragment上
        beginTransaction.add(R.id.container, fragment)
        //添加到事务里面
        beginTransaction.commitAllowingStateLoss()
    }
}

//Fragment
class FragmentStudy :Fragment(){
    var key1 = 2
    var key2 = "qqqqq"

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

//        return inflater.inflate(R.layout.activity_third, container, false)

        //创建一个textView
        val textView = TextView(context)
        textView.text = key2
        textView.setTextSize(22F)
        textView.gravity = Gravity.CENTER
        return textView
    }


    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        key1 = arguments?.getInt("key1") ?: 3
        key2 = arguments?.getString("key2") ?: "pppp"

        println("key1 = ${key1}")
        println("key2 = ${key2}")

        //该view，就是上面创建的TextView
        val textView = view as TextView
        textView.text = key2
    }

}