apiService.getUserInfo().enqueue(object :Callback<User>{
    override fun onResponse(call: Call<User>, response: Response<User>) {
        val user = response.body()
        tvNickName.text = user?.nickName
        apiService.getUnReadMsgCount(user?.token).enqueue(object :Callback<Int>{
            override fun onResponse(call: Call<Int>, response: Response<Int>) {
                val tvUnReadMsgCount = response.body()
                tvMsgCount.text = tvUnReadMsgCount.toString()
            }
        })
    }
})

mainScope.launch {
    val user = apiService.getUserInfoSuspend() //IO線程請(qǐng)求數(shù)據(jù)
    tvNickName.text = user?.nickName //UI線程更新界面
    val unReadMsgCount = apiService.getUnReadMsgCountSuspend(user?.token) //IO線程請(qǐng)求數(shù)據(jù)
    tvMsgCount.text = unReadMsgCount.toString() //UI線程更新界面
}

suspend fun getUserInfoSuspend() :User? {
    return withContext(Dispatchers.IO){
        //模擬網(wǎng)絡(luò)請(qǐng)求耗時(shí)操作
        delay(10)
        User("asd123", "userName", "nickName")
    }
}
suspend fun getUnReadMsgCountSuspend(token:String?) :Int{
    return withContext(Dispatchers.IO){
        //模擬網(wǎng)絡(luò)請(qǐng)求耗時(shí)操作
        delay(10)
        10
    }
}

suspend fun getUserInfo() : User {
    val user = User("asd123", "userName", "nickName")
    return user
}

fun getUserInfo(callback: Callback<User>): Any? {
    val user = User("asd123", "userName", "nickName")
    callback.onSuccess(user)
    return Unit
}

fun getUserInfo(cont: Continuation<User>): Any? {
    val user = User("asd123", "userName", "nickName")
    cont.resume(user)
    return Unit
}

@Nullable
public final Object getUserInfo(@NotNull Continuation $completion) {
   User user = new User("asd123", "userName", "nickName");
   return user;
}

internal abstract class BaseContinuationImpl() : Continuation<Any?> {
    public final override fun resumeWith(result: Result<Any?>) {
        //省略好多代碼
        invokeSuspend()
        //省略好多代碼
    }
    protected abstract fun invokeSuspend(result: Result<Any?>): Any?
}
internal abstract class ContinuationImpl(
    completion: Continuation<Any?>?,
    private val _context: CoroutineContext?
) : BaseContinuationImpl(completion) {
protected abstract fun invokeSuspend(result: Result<Any?>): Any?

//invokeSuspend() 這個(gè)方法是恢復(fù)的關(guān)鍵一步

suspend fun testCoroutine() {
    val user = apiService.getUserInfoSuspend() //掛起函數(shù)  IO線程
    tvNickName.text = user?.nickName //UI線程更新界面
    val unReadMsgCount = apiService.getUnReadMsgCountSuspend(user?.token) //掛起函數(shù)  IO線程
    tvMsgCount.text = unReadMsgCount.toString() //UI線程更新界面
}

fun testCoroutine(completion: Continuation<Any?>): Any? {
    // TestContinuation本質(zhì)上是匿名內(nèi)部類
    class TestContinuation(completion: Continuation<Any?>?) : ContinuationImpl(completion) {
        // 表示協(xié)程狀態(tài)機(jī)當(dāng)前的狀態(tài)
        var label: Int = 0
        // 兩個(gè)變量，對(duì)應(yīng)原函數(shù)的2個(gè)變量
        lateinit var user: Any
        lateinit var unReadMsgCount: Int
        // result 接收協(xié)程的運(yùn)行結(jié)果
        var result = continuation.result
        // suspendReturn 接收掛起函數(shù)的返回值
        var suspendReturn: Any? = null
        // CoroutineSingletons 是個(gè)枚舉類
        // COROUTINE_SUSPENDED 代表當(dāng)前函數(shù)被掛起了
        val sFlag = CoroutineSingletons.COROUTINE_SUSPENDED
        // invokeSuspend 是協(xié)程的關(guān)鍵
        // 它最終會(huì)調(diào)用 testCoroutine(this) 開啟協(xié)程狀態(tài)機(jī)
        // 狀態(tài)機(jī)相關(guān)代碼就是后面的 when 語句
        // 協(xié)程的本質(zhì)，可以說就是 CPS + 狀態(tài)機(jī)
        override fun invokeSuspend(_result: Result<Any?>): Any? {
            result = _result
            label = label or Int.Companion.MIN_VALUE
            return testCoroutine(this)
        }
    }
    // ...
    val continuation = if (completion is TestContinuation) {
        completion
    } else {
        //                作為參數(shù)
        //                   ↓
        TestContinuation(completion)

loop = true
while(loop) {
when (continuation.label) {
    0 -> {
        // 檢測(cè)異常
        throwOnFailure(result)
        // 將 label 置為 1，準(zhǔn)備進(jìn)入下一次狀態(tài)
        continuation.label = 1
        // 執(zhí)行 getUserInfoSuspend（第一個(gè)掛起函數(shù)）
        suspendReturn = getUserInfoSuspend(continuation)
        // 判斷是否掛起
        if (suspendReturn == sFlag) {
            return suspendReturn
        } else {
            result = suspendReturn
            //go to next state
        }
    }
    1 -> {
        throwOnFailure(result)
        // 獲取 user 值
        user = result as Any
        // 準(zhǔn)備進(jìn)入下一個(gè)狀態(tài)
        continuation.label = 2
        // 執(zhí)行 getUnReadMsgCountSuspend
        suspendReturn = getUnReadMsgCountSuspend(user.token, continuation)


        // 判斷是否掛起
        if (suspendReturn == sFlag) {
            return suspendReturn
        } else {
            result = suspendReturn
            //go to next state
        }
    }
    2 -> {
        throwOnFailure(result)
        user = continuation.mUser as Any
        unReadMsgCount = continuation.unReadMsgCount as Int
        loop = false
}
}