如何从iOS ViewController通信到KotlinComposable

Question

android

class CountdownViewModel : ViewModel() {
    private val totalTimeSeconds = 15 * 60 // 15 minutes in seconds
    private var remainingTime = totalTimeSeconds

    private val _time = MutableStateFlow(formatTime(remainingTime))
    val time: StateFlow<String> = _time.asStateFlow()

    private val _progress = MutableStateFlow(1f)
    val progress: StateFlow<Float> = _progress.asStateFlow()

    private val _isRunning = MutableStateFlow(false)
    val isRunning: StateFlow<Boolean> = _isRunning.asStateFlow()

    fun startTimer() {
        if (isRunning.value) return
        _isRunning.value = true
        viewModelScope.launch {
            while (remainingTime > 0 && isRunning.value) {
                delay(1000)
                remainingTime--
                _time.value = formatTime(remainingTime)
                _progress.value = remainingTime / totalTimeSeconds.toFloat()
            }
            _isRunning.value = false
        }
    }
    
    fun toggleTimer() {
        if (isRunning.value) stopTimer() else startTimer()
    }

    fun stopTimer() {
        _isRunning.value = false
        remainingTime = totalTimeSeconds
        _time.value = formatTime(remainingTime)
        _progress.value = 1f
    }

    private fun formatTime(seconds: Int): String {
        val minutes = seconds / 60
        val secs = seconds % 60
        return "%02d:%02d".format(minutes, secs)
    }
}

ios

class CountdownViewModel: ObservableObject {
    private let totalTimeSeconds = 10 * 60 // 10 minutes in seconds
    private var remainingTime: Int
    private var timer: Timer?

    u/Published var time: String
    @Published var progress: Float
    @Published var isRunning: Bool

    init() {
        self.remainingTime = totalTimeSeconds
        self.time = CountdownViewModel.formatTime(totalTimeSeconds)
        self.progress = 1.0
        self.isRunning = false
    }

    func startTimer() {
        if isRunning { return }
        isRunning = true
        timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { [weak self] _ in
            guard let self = self else { return }
            if self.remainingTime > 0 {
                self.remainingTime -= 1
                self.time = CountdownViewModel.formatTime(self.remainingTime)
                self.progress = Float(self.remainingTime) / Float(self.totalTimeSeconds)
            } else {
                self.stopTimer()
            }
        }
    }

    func toggleTimer() {
        if isRunning {
            stopTimer()
        } else {
            startTimer()
        }
    }

    func stopTimer() {
        isRunning = false
        timer?.invalidate()
        timer = nil
        remainingTime = totalTimeSeconds
        time = CountdownViewModel.formatTime(remainingTime)
        progress = 1.0
    }

    private static func formatTime(_ seconds: Int) -> String {
        let minutes = seconds / 60
        let secs = seconds % 60
        return String(format: "%02d:%02d", minutes, secs)
    }
}

androidui

class MainActivity : ComponentActivity() {
    private val viewModel by viewModels<CountdownViewModel>()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            val progress by viewModel.progress.collectAsStateWithLifecycle(initialValue = 0f)
            val time by viewModel.time.collectAsStateWithLifecycle()
            val isRunning by viewModel.isRunning.collectAsStateWithLifecycle()
        
            App(
                onButtonClicked = {
                    viewModel.toggleTimer()
                },
                progress = progress,
                time = time,
                isRunning = isRunning
            )
        }
    }
}

IOSUI

MainViewController.kt

fun FullMainViewController(
    time: String,
    progress: Float,
    isRunning: Boolean,
    toggleTimer: () -> Unit
) = ComposeUIViewController {
    App(
        onButtonClicked = toggleTimer,
        progress = progress,
        time = time,
        isRunning = isRunning
    )
}

ContentView.swift

struct ComposeView: UIViewControllerRepresentable {
    @ObservedObject var viewModel: CountdownViewModel

    func makeUIViewController(context: Context) -> UIViewController {
        return MainViewControllerKt.FullMainViewController(
            time: viewModel.time,
            progress: viewModel.progress,
            isRunning: viewModel.isRunning,
            toggleTimer: { viewModel.toggleTimer() }
        )
    }

    func updateUIViewController(
            _ uiViewController: UIViewController,
            context: Context
    ) {}
}

struct ContentView: View {
    @StateObject private var viewModel = CountdownViewModel()
    
    var body: some View {
        ComposeView(
            viewModel: viewModel
        )
        .ignoresSafeArea(.keyboard) // Compose has own keyboard handler
    }
}

问题

Android应用程序运行良好，但我无法找到一种使iOS上的合并更新的方法。我的意思是，我可以在ComposeView中添加一个

.id(viewModel.time)

，以便每次都被调用，但性能看起来很糟糕。还有其他方法可以从iOS中更新合并吗？

notes我知道你们中的一些人可能建议通过Kotlin共享相同的ViewModel，但我想避免这种情况。我正在考虑创建一个仅解决UI的解决方案，我希望能够将其作为UI库将其导入到Android和iOS中。

您必须将平台特定的代码放在数据层（

Https：//developer.android.com/topic/architecture#recommend--app-arch-）。

数据层

makeUIViewController

UI层

expect fun createTimer(): Timer

Answer 1

val timer = createTimer()