尝试更改观察者内部的 MutableLiveData 值时应用程序没有响应

Question

在这个应用“猜一猜”游戏中，我试图检测当用户到达 wordList 末尾时游戏何时结束，在 GameViewModel 中 _eventGameFinish val 负责

GameViewModel

class GameViewModel : ViewModel() {


    // The current word
    private val _word = MutableLiveData<String>()
    val word: LiveData<String>
        get() = _word


    // The current score
    private val _score = MutableLiveData<Int>()
    val score: LiveData<Int>
        get() = _score


    private val _eventGameFinish = MutableLiveData<Boolean>()
    val eventGameFinish : LiveData<Boolean>
            get()= _eventGameFinish


    // The list of words - the front of the list is the next word to guess
    private lateinit var wordList: MutableList<String>

    init {
        Log.i("GameViewModel", "GameViewModel created!")
        resetList()
        nextWord()
        _score.value = 0
        _eventGameFinish.value = false
    }

    /**
     * Resets the list of words and randomizes the order
     */
    private fun resetList() {
        wordList = mutableListOf(
            "queen",
            "hospital",
            "basketball",
            "cat",
            "change",
            "snail",
            "soup",
            "calendar",
            "sad",
            "desk",
            "guitar",
            "home",
            "railway",
            "zebra",
            "jelly",
            "car",
            "crow",
            "trade",
            "bag",
            "roll",
            "bubble"
        )
        wordList.shuffle()
    }

    /**
     * Moves to the next word in the list
     */
    private fun nextWord() {
        //Select and remove a word from the list
        if (wordList.isEmpty()) {
            _eventGameFinish.value = true
        } else {
            _word.value = wordList.removeAt(0)
        }
    }

    /** Methods for buttons presses **/

    fun onSkip() {
        _score.value = score.value?.minus(1)
        nextWord()
    }

    fun onCorrect() {
        _score.value = score.value?.plus(1)
        nextWord()
    }

    fun onGameFinishComplete(){
        _eventGameFinish.value = false
    }

    override fun onCleared() {
        super.onCleared()
        Log.i("GameViewModel", "GameViewModel destroyed")
    }
}

在 GameFragment 中，我在 eventGameFinish 上观察，然后调用 gameViewModel.onGameFinishComplete() 以在片段中仅执行一次操作

这里是 GameFragment class

class GameFragment : Fragment() {

    private lateinit var gameViewModel: GameViewModel


    private lateinit var binding: GameFragmentBinding

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {

        // Inflate view and obtain an instance of the binding class
        binding = DataBindingUtil.inflate(
            inflater,
            R.layout.game_fragment,
            container,
            false
        )

        Log.i("GameViewModelOf", "GameViewModelOf")
        gameViewModel = ViewModelProvider(this).get(GameViewModel::class.java)



        binding.correctButton.setOnClickListener {

            gameViewModel.onCorrect()

        }
        binding.skipButton.setOnClickListener {
            gameViewModel.onSkip()

        }


        gameViewModel.score.observe(viewLifecycleOwner, Observer { newScore ->
            binding.scoreText.text = newScore.toString()
        })

        gameViewModel.word.observe(viewLifecycleOwner, Observer { newWord ->
            binding.wordText.text = newWord

        })

        gameViewModel.eventGameFinish.observe(viewLifecycleOwner, Observer { eventGameFinish ->
            if (eventGameFinish) this.gameFinished()
            gameViewModel.onGameFinishComplete()
        })

        return binding.root

    }


    /**
     * Called when the game is finished
     */
    private fun gameFinished() {
//        val action = GameFragmentDirections.actionGameToScore(gameViewModel.score.value ?: 0)
//        findNavController(this).navigate(action)
        Toast.makeText(this.activity, "Game finished", Toast.LENGTH_SHORT).show()
    }
}

问题出在这一行 gameViewModel.onGameFinishComplete() 当我在 Observer 块中调用方法时运行应用程序没有任何异常响应，如果我删除了这个方法调用，应用程序是工作正常，但我无法在到达 wordList

末尾时更改 eventGameFinish 的值

Answer 1

您正在观察“eventGameFinish”，如果它是真的，它将调用 gameFinished() 方法和 onGameFinishComplete() 代码将新值设置为 eventGameFinish.so 观察者将再次观察到新值。现在它是假的，它将一次又一次地调用 gameViewModel() 并设置 false.that 是你收到 ANR 的原因。

因此仅当实时数据值为 true.OR 时才调用方法，在游戏结束后使用单独的 MutableLiveData 数据设置值。

  if (eventGameFinish) 
{
    this.gameFinished()
    gameViewModel.onGameFinishComplete()
}

尝试更改观察者内部的 MutableLiveData 值时应用程序没有响应

The app not responding when try to change MutableLiveData value inside observer

android

mvvm

kotlin

android-livedata

android-viewmodel