我正在实现MethodChannel，将值从Flutter端传递到KotlinAndroid本地代码。我遵循了这两个教程，它们的操作与我复制的完全相同：和
我在main.dart [Flutter]中的MethodChannel实现如下：

class _MyHomePageState extends State<MyHomePage> {
  static const frequencyChannel =
      MethodChannel('com.somdipdey.eoptomizer/frequency');
...
...
Future setFrequencyLevelCPU0Max() async {
    var sendMapMaxCPUFreq = <String, String>{
      "LITTLECPUMaxFreq": _LITTLECPUFreq.text.toString()
    };
    final String frequencyLevelCPU0Max = await frequencyChannel.invokeMethod(
        'setFrequencyLevelCPU0Max', sendMapMaxCPUFreq);
  }
}

在Kotlin端的MainActivity.kt中，MethodChannel实现的代码如下所示：

class MainActivity: FlutterActivity() {

    private val OPTIMIZATION_CHANNEL = "com.somdipdey.eoptomizer/frequency"
    private lateinit var channel: MethodChannel

    override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        channel = MethodChannel(flutterEngine.dartExecutor.binaryMessenger, OPTIMIZATION_CHANNEL)
        channel.setMethodCallHandler { call, result ->
            if (call.method == "setFrequencyLevelCPU0Max" || call.method == "setFrequencyLevelCPU0Min" || call.method == "setFrequencyLevelCPU4Min") {
                var arguments = call.arguments() as Map<String,String>
                var LITTLECPUMaxFreq = arguments["LITTLECPUMaxFreq"].toString() ?: "1766400"
                setFrequencyLevelCPU0Max(LITTLECPUMaxFreq)
                result.success("Optimizing frequencies on CPU0")
            }
        }
    }
}

当我尝试构建/运行项目时，我在Kotlin端收到以下错误：
MainActivity.kt:（27，38）：类型不匹配：推断的类型为Map〈String，String〉？但应为Map〈String，String〉
下列程式码行会发生这个错误：

var arguments = call.arguments() as Map<String,String>

如何解决此问题？