Android Jetpack Compose + OKHttp

Question

在尝试将 Jetpack Compose 与 OKHttp 结合使用时，我正在发出一个 HTTP 请求，当它返回时（如果成功）我想启动一个新活动，否则向用户显示一条 toast 错误消息。

但是，我不确定实际上如何

startActivity

。我收到以下错误：

fun performLogin(loginViewModel: LoginViewModel, context: Context) {
    try {
        val email = loginViewModel.email.value
        val password = loginViewModel.password.value

        val client = OkHttpClient()

        val serverUri = SystemService.getAPIUri()
        val loginUri = "$serverUri/login"

        val data = """
            "email": "$email",
            "password": "$password"
            """.trimIndent()

        val formBody = FormBody.Builder()
            .add("email", email.toString())
            .add("password", password.toString())
            .build()

        val body = data.toRequestBody("application/json; charset=utf-8".toMediaTypeOrNull())

        val request = Request.Builder()
            .url(loginUri)
            .post(formBody)
            .build()

        val call = client.newCall(request)

        call.enqueue(object: Callback {
            override fun onFailure(call: Call, e: IOException) {
                e.printStackTrace()
            }

            override fun onResponse(call: Call, response: Response) {
                response.use {
                    if (!response.isSuccessful) throw IOException("Unexpected code $response")

                    for ((name, value) in response.headers) {
                        println("$name: $value")
                    }

                    println(response.body!!.string())

                    Looper.prepare()

                    // Gives an error here
                    loginCallback()

                    Looper.loop()

                }
            }

        })
    } catch (e: Exception) {
        println("Login Error: ")
        println(e)

        val toast = Toast.makeText(context, "Error Logging In", Toast.LENGTH_LONG)
        toast.show()
    }
}

@Composable
fun loginCallback() {
    val context = LocalContext.current

    context.startActivity(Intent(context, MainActivity::class.java))
}

如果出现 HTTP 错误，toast 将会崩溃，提示我必须在主线程中运行它。

并且调用 loginCallback() 不起作用，正如它所说的

@Composable invocations can only happen from the context of a @Composable function

Answer 1

由于 onResponse 不在可组合范围内，因此在 .enqueue(...) 之外声明

val coroutineScope = rememberCoroutineScope()

并在

coroutineScope.launch { }

内启动所需的代码，Toast.makeText(...) 也是如此。

Answer 2

尝试在 Kotlin 中使用函数作为参数，将 ViewModel 中的 toast 函数传递给 OKhttp 客户端，并在 onResponse 或 onFailure 中使用该函数作为回调

fun toast(msg:String){
displayToast(msg)
}

fun performLogin(loginViewModel: LoginViewModel, context: Context, displayToast: 
    (String) -> Unit) {
       ....

    override fun onResponse(call: Call, response: Response) {
        displayToast("Msg you want to display")
    }

}