android - 属性委托(delegate)必须有一个 'getValue(Nothing?, KProperty*>)' 方法

Question

我正在尝试根据用户的选择来设置我的应用程序的主题。它可以是深色主题或浅色主题。

我将 viewModel 创建为:

class ThemeViewModel(application: Application) : AndroidViewModel(application) {
    private val _darkMode = MutableLiveData<Boolean>(true)
    val darkMode : LiveData<Boolean>
        get() = _darkMode


    fun setDarkMode(isDarkMode:Boolean){
        _darkMode.value = isDarkMode
    }

    fun getDarkMode():Boolean = _darkMode.value!!

}

我将主题创建为:

@Composable
fun VoodleeTheme(
    darkTheme: Boolean,
    content: @Composable () -> Unit
) {
    MaterialTheme(
        colors = if (darkTheme) DarkColors else LightColors,
        content = content
    )

我将 setContent 用作:

setContent {
  MyApp {
    val doDark: Boolean by 
    themeViewModel.darkMode.observeAsState(Boolean) //this line gives error

    VoodleeTheme(darkTheme = doDark) {
    ProgressNavigation(themeViewModel)
        }
    }
}

请帮助我解决这个问题。

Answer 1

添加，

import androidx.compose.runtime.getValue

这是 MutableState<T> 的扩展函数实现使用 by 的要求在val .