var value by remember { mutableStateOf(default) } 会产生错误，为什么？

Question

我指的是 https://developer.android.com/jetpack/compose/state 中的示例。 当我编码时

var expanded by remember { mutableStateOf(false) }

错误说明

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

下面的方法虽然有效

val expanded = remember { mutableStateOf(false) }

// OR

val (expanded, setExpanded) = remember { mutableStateOf(false) }

Answer 1

显然，我必须包含这些导入内容

import androidx.compose.runtime.getValue
import androidx.compose.runtime.setValue

自动导入不会在测试版中自动推荐它 Android Studio 4.2

如果您使用实时数据，请考虑以下导入

import androidx.compose.runtime.livedata.observeAsState