android fragment View 模型初始化失败

Question

我正在尝试使用 kotlin 在 android 中实现数据绑定(bind):

override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        mBinding = DataBindingUtil.inflate<ViewDataBinding>(
            inflater, R.layout.fragment_login, container, false
        ) as FragmentLoginBinding
        val view: View = mBinding.root
        mBinding.login?.invoke(viewModel)
        return view
    }

但它说 lateinit 属性 viewModel 尚未初始化 在运行时。我该如何解决这个问题？

在 fragment 中初始化将起作用

如果你们给我提供从父级初始化的 View 模型会更好，父级是一个 Activity

Answer 1

如果你想在Activity中初始化viewModel并在fragment中使用你可以这样:
主要 Activity .kt:

private lateinit var viewModel: MainActivityVM

override fun onCreate(savedInstanceState: Bundle?)
{
    viewModel = ViewModelProvider(this).get(MainActivityVM::class.java)

    super.onCreate(savedInstanceState)
}

你的 fragment .kt:

private lateinit var binding: YourFragmentBinding
private lateinit var viewModel: MainActivityVM

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View?
{
    binding = DataBindingUtil.inflate(
        inflater,
        R.layout.fragment_your, container, false
    )

    binding.lifecycleOwner = this

    viewModel = ViewModelProvider(requireActivity()).get(MainActivityVM::class.java)

    //here You can use Your viewModel

    return binding.root
}