5

我的ViewModelFactory：

class ViewModelFactory @Inject constructor(
    private val viewModelMap: MutableMap<Class<out ViewModel>, ViewModelAssistedFactory<out ViewModel>>,
    owner: SavedStateRegistryOwner,
    defaultArgs: Bundle?
) : AbstractSavedStateViewModelFactory(owner, defaultArgs) {

    @Throws(IllegalStateException::class)
    @Suppress("UNCHECKED_CAST")
    override fun <T : ViewModel?> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T {
        return viewModelMap[modelClass]?.create(handle) as? T ?: throw IllegalStateException("Unknown ViewModel class")
    }
}

活动：

@Inject
lateinit var viewModelFactory: ViewModelFactory
protected val viewModel: ViewModel by lazy { ViewModelProvider(this, viewModelFactory).get(getViewModelClass()) }

视图模型：

@AssistedInject.Factory
interface Factory : ViewModelAssistedFactory<SplashViewModel>

我想知道如何动态提供 defaultArgs 而不是：

活动模块

@Module
    companion object {
        @JvmStatic
        @Nullable
        @Provides
        fun provideDefaultArgs(): Bundle? {
            return null
        }
    }

这个想法是有可能向 ViewModel 发送一个参数，比方说一个 DetailActivity 的 ID。通常我使用“init”方法，但如果我可以使用StateHandle map会更好。像这样和这样的东西。

说得通？是否可以？

4

1 回答 1

5

我遇到了2个解决方案：

解决方案 A：

将我们的 ViewModelFactory 更改为：

class ViewModelFactory @Inject constructor(
    private val viewModelMap: MutableMap<Class<out ViewModel>, ViewModelAssistedFactory<out ViewModel>>
) {
    fun create(owner: SavedStateRegistryOwner, defaultArgs: Bundle? = null): AbstractSavedStateViewModelFactory {
        return object : AbstractSavedStateViewModelFactory(owner, defaultArgs) {
            @Suppress("UNCHECKED_CAST")
            override fun <T : ViewModel?> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T {
                return viewModelMap[modelClass]?.create(handle) as? T ?: throw IllegalStateException("Unknown ViewModel class")
            }
        }
    }
}

最后：

@Inject
lateinit var viewModelFactory: ViewModelFactory
protected val viewModel: ViewModel by lazy { ViewModelProvider(this, viewModelFactory.create(this, args).get(getViewModelClass()) }

此外，我们可以将 ActivityModule 简化为（示例）：

@AssistedModule
@Module(includes = [AssistedInject_SplashActivityModule::class])
abstract class SplashActivityModule{

    @Binds
    @IntoMap
    @ViewModelKey(SplashViewModel::class)
    abstract fun bindFactory(factory: SplashViewModel.Factory): ViewModelAssistedFactory<out ViewModel>
}

Tomáš Mlynarič的这篇文章帮助解决了这个问题。

解决方案 B：

创建一个Factory没有注入依赖项：

class ViewModelFactoryAlt<out V : ViewModel>(
    private val viewModelFactory: ViewModelAssistedFactory<V>,
    owner: SavedStateRegistryOwner,
    defaultArgs: Bundle? = null
) : AbstractSavedStateViewModelFactory(owner, defaultArgs) {

    @Suppress("UNCHECKED_CAST")
    override fun <T : ViewModel> create(key: String, modelClass: Class<T>, handle: SavedStateHandle): T {
        return viewModelFactory.create(handle) as T
    }
}

创建我们的ViewModelAssitedFactory喜欢：

class HelloWorldViewModelFactory @Inject constructor(
    private val dependencyA: DependencyA,
    ...
) : ViewModelAssistedFactory<HelloWorldViewModel> {
    override fun create(stateHandle: SavedStateHandle): HelloWorldViewModel {
        return HelloWorldViewModel(stateHandle, dependencyA, ...)
    }
}

最后：

@Inject
lateinit var factory: HelloWorldViewModelFactory
private val viewModel: HelloWorldViewModel by viewModels { ViewModelFactoryAlt(factory, this, intent.extras) }

Elye的这篇文章帮助解决了这个问题。

于 2020-04-21T21:15:19.547 回答