关于android：从AndroidViewModel扩展时如何使用ViewModelProvider.Factory

How to use a ViewModelProvider.Factory when extends from AndroidViewModel

我想向我的ViewModel发送一个额外的参数，但这是从AndroidViewModel扩展过来的。
如何将此参数添加到ViewModelFactory类中？

ViewModel

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class ProjectViewModel(application: Application) : AndroidViewModel(application) {

// need a param for project id...
}

ViewModelFactory

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class ProjectViewModelFactory(val projectId: Int): ViewModelProvider.Factory {

override fun <T : ViewModel?> create(modelClass: Class< T >): T {
// need to send this...
return ProjectViewModel(projectId) as T
}
}

注意：我注意到在文档中它说：AndroidViewModel子类必须具有一个接受Application作为唯一参数的构造函数。

所以我不知道是否可以(或者很好)去做我想做的事情。

相关讨论

我引用了AndroidViewModelFactory类，并像这样使用它

1.AndroidViewModelFactory

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class AndroidViewModelFactory private constructor(
private val mApplication: Application,
private val mName: String
) : ViewModelProvider.NewInstanceFactory() {

override fun <T : ViewModel?> create(modelClass: Class< T >): T {
return if (AndroidViewModel::class.java.isAssignableFrom(modelClass)) {
try {
modelClass.getConstructor(
Application::class.java, String::class.java
).newInstance(mApplication, mName)
} catch (e: Exception) {
throw RuntimeException("Cannot create an instance of $modelClass", e)
}
} else super.create(modelClass)
}

companion object {
private var sInstance: AndroidViewModelFactory? = null
fun getInstance(
application: Application,
name: String
): AndroidViewModelFactory {
if (sInstance == null) {
sInstance = AndroidViewModelFactory(application, name)
}
return sInstance as AndroidViewModelFactory
}
}
}

2.ViewModelFactory

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object ViewModelFactory {

fun <T : ViewModel?> createViewModel(
activity: FragmentActivity,
application: Application,
name: String,
cls: Class< T >?
): T {
return ViewModelProvider(
activity,
AndroidViewModelFactory.getInstance(application, name)
).get(cls!!)
}
}

3.NameViewModel

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class NameViewModel(application: Application, name: String) : AndroidViewModel(application) {

val name = ObservableField<String>()

init {
this.name.set(name)
}
}

4.NameActivity

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class NameActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val binding =
DataBindingUtil.setContentView(this, R.layout.activity_name) as ActivityNameBinding
val viewModel = ViewModelFactory.createViewModel(
this,
application,
"AndroidViewModel",
NameViewModel::class.java
)
binding.viewModel = viewModel
}
}

5.activity_name

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