我可以消除 Android 片段中的视图模型和视图绑定样板代码吗?

Can I eliminiate viewmodel and viewbinding boilerplate code in my Android Fragments?

我发现自己为我创建的每个新片段编写样板代码。 这包括设置 viewmodel 和 viewbinding,这是我的代码的两个不同部分,彼此不依赖,因此其中一个的解决方案仍然很棒。

片段代码示例:

class MyFragment : Fragment() {

    // View binding
    private var _binding: FragmentMyBinding? = null

    // View model
    private lateinit var model : MyViewModel

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Model init
        model = ViewModelProvider(this).get(MyViewModel::class.java)

        //binding init
        _binding = FragmentMyBinding.inflate(inflater, container, false)

        return _binding!!.root
    }

}

class MyViewModel : ViewModel()

正如 ViewModel documentation page, Kotlin code should not use ViewModelProvider(this), but instead use by viewModels() 上所见,它是 fragment-ktx 依赖项的一部分。这取代了 lateinit var model 用法并且必须在 onCreateView() 中执行任何操作,这意味着您的片段变为:

class MyFragment : Fragment() {

    // View binding
    private var _binding: FragmentMyBinding? = null

    // View model
    private val model: MyViewModel by viewModels()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        //binding init
        _binding = FragmentMyBinding.inflate(inflater, container, false)

        return _binding!!.root
    }
}

您可以采用 this one 之类的方法,完全避免绑定。这种方法意味着您的片段将是:

class MyFragment : Fragment(R.layout.my_fragment) {

    // View model
    private val model: MyViewModel by viewModels()

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        val binding = FragmentMyBinding.bind(view)
        // Now use the binding and your ViewModel
    }
}

另一种选择是将 AutoClearedValue 复制到您的项目中并使用它,这会使它看起来像:

class MyFragment : Fragment() {

    // View binding
    private var binding by autoCleared<FragmentMyBinding>()

    // View model
    private val model: MyViewModel by viewModels()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentMyBinding.inflate(inflater, container, false)
        // Now use the binding and your ViewModel

        return binding.root
    }
}

此时,无论使用哪种解决方案,您都最多使用 3 行共享代码,所有这些代码行都不相同,因此尝试构建基本片段并处理泛型会使事情变得更加复杂。我不会建议这样做。