输入“状态<列表<用户>?"没有方法“getValue(Nothing?, KProperty<*>)"，因此它不能作为委托 [英] Type &#39;State&lt;List&lt;User&gt;?&gt;&#39; has no method &#39;getValue(Nothing?, KProperty&lt;*&gt;)&#39; and thus it cannot serve as a delegate

问题描述

我正在尝试使用 jetpack compose 中的 observeAsState 从 LiveData 获取值，但我收到一个奇怪的错误

I'm trying to get a value from LiveData with observeAsState in jetpack compose, but I get a weird error

输入状态<列表?>"没有方法 'getValue(Nothing?,KProperty<*>)'，因此它不能作为委托

Type 'State<List?>' has no method 'getValue(Nothing?, KProperty<*>)' and thus it cannot serve as a delegate

代码

@Composable
fun UserScreen(userViewModel:UserViewModel){
    val items: List<User> by userViewModel.fetchUserList.observeAsState()
    UserList(userList = items)
}

class UserViewModel: ViewModel() {

    private val dataSource = UserDataSource()
    val fetchUserList = liveData {
        emit(dataSource.dummyUserList)
    }
}

推荐答案

如果您收到未定义observeAsState 或 getValue 的编译器错误，请确保您有以下导入:

If you get a compiler error that observeAsState or getValue are not defined make sure you have the following imports:

import androidx.compose.runtime.getValue

import androidx.compose.runtime.livedata.observeAsState

此信息来自在 Jetpack Compose 中使用状态"代码实验室.

This information is from Step #4 in the "Using State in Jetpack Compose" codelab.

这篇关于输入“状态<列表<用户>?"没有方法“getValue(Nothing?, KProperty<*>)"，因此它不能作为委托的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！