android - ViewModel 中未触发 Activity 中的生命周期

Question

每当调用 Activity 的 onCreate 时，我都试图在 viewModel 中执行一个方法（有趣的 onCreateViewModel()）。但是该方法没有被执行。

视图模型

class MainActivityViewModel(startingCount : Int) : ViewModel(), LifecycleObserver {
    var count = 0

    init {
        count = startingCount
    }

    fun getCurrentCount(): Int{
        return count
    }

    fun getUpdatedCount(): Int {
        count ++
        return count
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
    public fun onCreateViewModel(){
        Log.i("Jts","   ViewModel created")
    }
}

活动

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding
    private var user = User("Jeffin T", "26")
    private lateinit var mainActivityViewModel: MainActivityViewModel
    private lateinit var mainActivityViewModelFactory: MainActivityViewModelFactory


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
//        mainActivityViewModel = ViewModelProviders.of()
        mainActivityViewModelFactory = MainActivityViewModelFactory(123)
        mainActivityViewModel = ViewModelProviders.of(this, mainActivityViewModelFactory)
            .get(MainActivityViewModel::class.java)
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        binding.tvName.text = mainActivityViewModel.getCurrentCount().toString()
        binding.user = user
        binding.btnName.setOnClickListener {
            binding.tvName.text = mainActivityViewModel.getUpdatedCount().toString()
        }
    }

    private fun displayGreeting() {
        binding.apply { tvName.setText("Hello! " + user?.name) }
    }
}

标签： androidkotlinandroid-jetpackandroid-viewmodel

Answer 1

您必须将视图模型添加为活动生命周期的观察者。你需要在你的活动中添加这个

getLifecycle().addObserver(viewModel)

更多信息在这里