Android 从活动共享视图模型以使用 hilt 组合函数

以docs为基数.

函数的作用是:返回现有的视图模型或creates a new one scoped to the current navigation graph present on the NavController back stack.该函数可以 Select 性地接受 NavBackStackEntry将视图模型的范围设置为父后台堆栈条目.

事实证明，当工厂是导航图的一部分时，它们会创建一个新的视图模型实例.但是，因为您已经发现要使它工作，您必须指定视图模型StoreOwner，所以我根据最近对这post的回答采取了一种方法，并创建了当前活动的CompostionLocal，因为它将Component活动扩展为视图模型StoreOwner本身.

这是我的简短try ，用可能的修复方法重现您的问题.

活动

@AndroidEntryPoint
class Hilt活动视图模型活动 : Component活动() {

    private val my视图模型: 活动Scoped视图模型 by viewModels()

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

        setContent {
                CompositionLocalProvider(Local活动 provides this@Hilt活动视图模型活动) {
                    Log.e("活动Scoped视图模型", "Hashcode: ${my视图模型.hashCode()} : 活动 Scope")
                    Hilt活动SampleNavHost()
            }
        }
    }
}

视图模型

@Hilt视图模型
class 活动Scoped视图模型 @Inject constructor(): 视图模型() {}

Local 活动 Composition

val Local活动 = staticCompositionLocalOf<Component活动> {
    error("Local活动 is not present")
}

简单导航图

enum class HiltSampleNavHostRoute {
    DES_A, DES_B
}

@Composable
fun Hilt活动SampleNavHost(
    modifier: Modifier = Modifier,
    navController: NavHostController = rememberNavController(),
    startDestination: String = HiltSampleNavHostRoute.DES_A.name
) {
    NavHost(
        modifier = modifier,
        navController = navController,
        startDestination = startDestination
    ) {

        composable(HiltSampleNavHostRoute.DES_A.name) {
            DestinationScreenA()
        }

        composable(HiltSampleNavHostRoute.DES_B.name) {
            DestinationScreenB()
        }
    }
}

屏风

// here you can use the Local 活动 as the 视图模型StoreOwner
@Composable
fun DestinationScreenA(
    my视图模型Param: 活动Scoped视图模型 = hilt视图模型(Local活动.current)
    // my视图模型Param: 活动Scoped视图模型 = viewModel(Local活动.current)
) {
    Log.e("活动Scoped视图模型", "Hashcode: ${my视图模型Param.hashCode()} : Composable Scope")
}

@Composable
fun DestinationScreenB(
    modifier: Modifier = Modifier
) {}

Or better yet, like from this answer by Phil Dukhov, you can use Local视图模型StoreOwner as the parameter when you invoke the builder.

相同的导航主机

@Composable
fun Hilt活动SampleNavHost(
    ...
) {

    val viewModelStoreOwner = checkNotNull(Local视图模型StoreOwner.current) {
        "No 视图模型StoreOwner was provided via Local视图模型StoreOwner"
    }

    NavHost(
        modifier = modifier,
        navController = navController,
        startDestination = startDestination
    ) {

        composable(HiltSampleNavHostRoute.DES_A.name) {
            DestinationScreenA(
                my视图模型Param = viewModel(viewModelStoreOwner)
            )
        }

        ...
    }
}

来自活动的日志(log)和NAV图中的Composable都显示相同的哈希码

E/活动Scoped视图模型: Hashcode: 267094635 : 活动 Scope
E/活动Scoped视图模型: Hashcode: 267094635 : Composable Scope

Also have a look at Thracian's answer. It has a very detailed explanation about Component活动, and based from it I think my first proposed solution would probably work in your case.