如何实现 ViewModel 保存状态

Question

所以我尝试在我的应用程序上实现 viewModel，但它仍然以相同的方式运行。 我想保存我的游戏的当前视图，但是由于应该保存的部分是在一个保存视图的函数中，所以我无法移动它。

这是一些代码。

片段

class GamePlay1Fragment : Fragment() {

//    lateinit var front_anim: AnimatorSet
//    lateinit var back_anim: AnimatorSet

    private lateinit var viewModel: GP1ViewModel
    private lateinit var pieces: List<ImageView>



    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding: Gameplay1FragmentBinding = DataBindingUtil.inflate(
            inflater,
            R.layout.gameplay1_fragment,
            container, false)



        viewModel = ViewModelProvider(this).get(GP1ViewModel::class.java)


        binding.backButtonView.setOnClickListener { v: View ->
            v.findNavController().navigate(GamePlay1FragmentDirections.actionGamePlay1FragmentToLobbyFragment())
        }


        pieces = listOf(binding.card1back, binding.card2back, binding.card3back, binding.card4back,
            binding.card5back,binding.card6back, binding.card7back,
            binding.card8back, binding.card9back, binding.card10back, binding.card11back,
            binding.card12back)

        viewModel.gameCards = pieces.indices.map { index ->
            GameCard(viewModel.images[index])
        }


            pieces.forEachIndexed { index, piece ->
                piece.setOnClickListener {

                    viewModel.updatingModels(index)

                    updatingViews()
                }
            }



        return binding.root
    }

    private fun updatingViews() {
        viewModel.gameCards.forEachIndexed { index, gameCard ->
            val piece = pieces[index]
            piece.setImageResource(if (gameCard.isFacedUp) gameCard.id else allcardbacks)
        }
    }


}

视图模型

class GP1ViewModel() : ViewModel() {

        lateinit var gameCards: List<GameCard>
        private var indexOfSelectedPiece: Int? = null



    val images = mutableListOf(
        R.drawable.memorybatcardfront,
        R.drawable.memorycatcardfront,
        R.drawable.memorycowcardfront,
        R.drawable.memorydragonfront,
        R.drawable.memorygarbagemancardfront,
        R.drawable.memoryghostdogcardfront
    )

    init {
        images.addAll(images)
        images.shuffle()
        Log.e(TAG, "ViewModel Created:")
    }






     fun updatingModels(position: Int) {
        val gameCard = gameCards[position]

        if (gameCard.isFacedUp) return


        if (indexOfSelectedPiece == null) {
            restoreGameCards()
            indexOfSelectedPiece = position

        }
        else {
            checkingForMatch(indexOfSelectedPiece!!, position)
            indexOfSelectedPiece = null
        }
        gameCard.isFacedUp = !gameCard.isFacedUp
    }

    private fun restoreGameCards() {
        val handler = Handler()
        for (gameCard in gameCards) {
            if (!gameCard.isMatched) {
                handler.postDelayed(runnable, 1000)
                gameCard.isFacedUp = false

            }

        }
    }

    private fun checkingForMatch(position1: Int, position2: Int) {
        if (gameCards[position1].id == gameCards[position2].id) {
            gameCards[position1].isMatched = true
            gameCards[position2].isMatched = true
        }
    }

    private val runnable = Runnable(){
        kotlin.run {
        }
    }


}

我假设需要保存的部分是片段中的更新视图（），但我无法移动它，因为它还处理图像视图数组（S.O.C）。欢迎任何想法，谢谢。

Answer 1

您的 viewModel 正在使用片段引用。相反，它应该使用活动引用。

viewModel = ViewModelProvider(this).get(GP1ViewModel::class.java)

由于您使用的是片段引用，一旦片段被销毁，它将被销毁，因此数据不会被持久化。

需要注意的另一点是，如果您愿意，可以使用 SharedViewModel 方法在多个片段实例之间共享数据。