无法从活动中观察视图模型中的livedata集

override fun onStart() {
    super.onStart()
    viewModel.liveData.observe(this, Observer { data ->
        // 更新UI
    })
}

viewModel.liveData.observe(this as LifecycleOwner, Observer { data ->
    // 更新UI
})

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="viewModel"
            type="com.example.app.ViewModel" />
    </data>
    <!-- 布局内容 -->
</layout>

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
    binding.viewModel = viewModel
    binding.lifecycleOwner = this
}

class MainActivity : AppCompatActivity() {
    private lateinit var viewModel: ViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewModel = ViewModelProvider(this).get(ViewModel::class.java)
        // 其他初始化代码
    }
}

class MainActivity : AppCompatActivity() {
    private lateinit var viewModel: ViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        viewModel = ViewModelProvider(this).get(ViewModel::class.java)
        binding.viewModel = viewModel
        binding.lifecycleOwner = this
    }
}

class ViewModel : ViewModel() {
    val liveData = MutableLiveData<List<String>>()

    init {
        // 模拟数据更新
        liveData.value = listOf("Item 1", "Item 2", "Item 3")
    }
}