最近在我的应用中，我一直在使用简单的导航组件参数传递。因为我已经添加了Hilt ViewModel，我遇到了一些叫做saveStateHandle的东西，显然我可以很容易地在屏幕之间传递参数。我怎么能做到呢?我实现的代码在我的HiltViewModel
@HiltViewModel
class ExerciseViewModel @Inject constructor(
private val repository: ExerciseRepository,
savedStateHandle: SavedStateHandle
) : ViewModel() {
val data: MutableState<DataOrException<List<Exercise>, Boolean, Exception>> =
mutableStateOf(
DataOrException(null, true, Exception(""))
)
val muscleGroup: String? = savedStateHandle[Constants.MUSCLE_GROUP_KEY]
private val _exerciseListFromDb = MutableStateFlow<List<Exercise>>(emptyList())
val exerciseListFromDb = _exerciseListFromDb.asStateFlow()
init {
getExercises()
viewModelScope.launch(Dispatchers.IO) {
repository.getAllExercisesFromDb().collect() {
_exerciseListFromDb.value = it
}
}
}
private fun getExercises() {
viewModelScope.launch {
data.value.loading = true
data.value = repository.getExercises()
if (data.value.data.toString().isNotEmpty())
data.value.loading = false
}
}
fun insertExerciseToDb(exercise: Exercise) = viewModelScope.launch {
repository.insertExerciseToDb(exercise)
}
fun deleteExerciseFromDb(exercise: Exercise) = viewModelScope.launch {
repository.deleteExerciseFromDb(exercise)
}
}
我想在屏幕之间传递muscleGroup参数主屏幕->SampleExercisesScreen。我如何发送参数从主屏幕到HiltViewModelExerciseViewModel，然后使用它在SampleExercisesScreen和其他屏幕?
@Composable
fun HomeScreen(navController: NavController) {
Surface(modifier = Modifier.fillMaxSize(),
color = AppColors.mBackground) {
Column {
Header()
Row(modifier = Modifier
.fillMaxWidth()
.padding(top = 50.dp)){
MuscleButton(modifier = Modifier.weight(1f), icon = R.drawable.body, muscleGroup = "Chest", navController)
MuscleButton(modifier = Modifier.weight(1f), icon = R.drawable.male, muscleGroup = "Back", navController)
MuscleButton(modifier = Modifier.weight(1f), icon = R.drawable.shoulder, muscleGroup = "Shoulders", navController)
}
Row(modifier = Modifier.fillMaxWidth()){
MuscleButton(modifier = Modifier.weight(1f), icon = R.drawable.muscle, muscleGroup = "Biceps", navController)
MuscleButton(modifier = Modifier.weight(1f), icon = R.drawable.triceps, muscleGroup = "Triceps", navController)
MuscleButton(modifier = Modifier.weight(1f), icon = R.drawable.leg, muscleGroup = "Legs", navController)
}
}
}
},
@Composable
fun SampleExerciseScreen(navController: NavController, muscleGroup: String, exerciseList: List<Exercise>?) {
val mExerciseList = exerciseList!!.filter { it.muscle == muscleGroup }
Log.d("TEST", "$mExerciseList, $muscleGroup")
Surface(modifier = Modifier.fillMaxSize(),
color = AppColors.mBackground) {
Column {
MyTopBar(navController = navController)
LazyColumn(Modifier.weight(1f)){
items(mExerciseList) {
ExerciseRow(exercise = it)
}
}
GoToButton(navController = navController, text = "YOUR EXERCISES", route = Screen.UserExercises.passMuscleGroup(muscleGroup))
}
}
}NavGraph
@Composable
fun SetupNavGraph(navController: NavHostController, viewModel: ExerciseViewModel) {
val exerciseList = viewModel.data.value.data?.toList()
val exerciseListFromDb = viewModel.exerciseListFromDb.collectAsState().value
val muscleGroup = viewModel.muscleGroup
NavHost(navController = navController, startDestination = Screen.Home.route) {
composable(
route = Screen.Home.route
) {
HomeScreen(navController = navController)
}
composable(
route = Screen.SampleExercise.route,
) {
SampleExerciseScreen(
navController = navController,
muscleGroup = muscleGroup.toString(),
exerciseList = exerciseList
)
}
composable(
route = Screen.UserExercises.route,
arguments = listOf(navArgument(MUSCLE_GROUP_KEY) {
type = NavType.StringType
})
) {
UserExercisesScreen(
navController = navController,
muscleGroup = it.arguments?.getString(MUSCLE_GROUP_KEY).toString(),
viewModel = viewModel,
exerciseListFromDb = exerciseListFromDb
)
}
composable(
route = Screen.Add.route,
arguments = listOf(navArgument(MUSCLE_GROUP_KEY) {
type = NavType.StringType
})
) {
AddScreen(
navController = navController, muscleGroup = it.arguments?.getString(MUSCLE_GROUP_KEY).toString(),
viewModel = viewModel
)
}
}
}
我在这里有一篇博客文章对此进行了解释:https://www.francescvilarino.com/passing-arguments-to-screens-in-jetpack-compose
但是基本上你必须从SavedStateHandle中检索视图模型中的参数，使用你在路由中为每个参数使用的key。
navController.navigate(buildTwoRoute(argument))
然后
@HiltViewModel
class TwoViewModel @Inject constructor(
savedStateHandle: SavedStateHandle,
) : ViewModel() {
init {
val argument = savedStateHandle.get<String>(DestinationOneArg).orEmpty()
}
}