ViewModel和ViewModelProvider

依赖

//ViewModel
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0'

创建ViewModel

class GameViewModel : ViewModel() {
   init {
       Log.i("GameViewModel", "GameViewModel created!")
   }
}

关联并初始化

声明

private lateinit var viewModel: GameViewModel

初始化

viewModel = ViewModelProvider(this).get(GameViewModel::class.java)

Important: Always use ViewModelProvider to create ViewModel objects rather than directly instantiating an instance of ViewModel.

使用ViewModelFactory

class ScoreViewModel(finalScore: Int) : ViewModel() {
   // The final score
   var score = finalScore
   init {
       Log.i("ScoreViewModel", "Final score is $finalScore")
   }
}

class ScoreViewModelFactory(private val finalScore: Int) : ViewModelProvider.Factory {
    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
        if (modelClass.isAssignableFrom(ScoreViewModel::class.java)) {
            return ScoreViewModel(finalScore) as T
        }
        throw IllegalArgumentException("Unknown ViewModel class")
    }
}