Fragment类，MVVM，视图模型中的未解析参考（vars）

Question

我正在学习有关使用Kotlin开发Android应用程序的UDACITY免费课程，而我实际上是在本课程的Viewmodel / MVVM部分，即实现Viewmodel类以更好地分离关注点。所以无论如何，我现在就封锁了。我正在进行的练习是关于创建Viewmodel类并将变量和函数从Fragment类传递到这个新创建的类的。我逐步按照教程进行操作，检查所提供的git diff的正确答案，但仍然发现自己被未解决的参考错误所阻止。

更改代码之前，我必须更新Gradle模块文件以使用ViewModel

//ViewModel
implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'

然后我必须在Fragment类中声明Viewmodel对象

gameViewModel = ViewModelProviders.of(this).get(GameViewModel::class.java)

不推荐使用ViewModelProviders，以前的课程，在搜索后，我不得不将其更改为

gameViewModel = ViewModelProvider(this).get(GameViewModel::class.java)

这似乎是正确的方法，但是我仍然对变量word（gameViewModel。word）和得分（gameViewModel。score] >）在Fragment类中，无法编译。我不知道我是否正确声明了Viewmodel对象，或者是否缺少其他内容...

我没有ViewModel类函数（即gameViewModel.onCorrect（）和gameViewModel.onSkip（）的问题，未解决的参考）。它们似乎在Fragment类中已正确声明和调用，这使我对变量，单词和分数产生了疑问...

我的片段类

package com.example.android.guesstheword.screens.game

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import androidx.lifecycle.ViewModelProvider
import androidx.navigation.fragment.NavHostFragment.findNavController
import com.example.android.guesstheword.R
import com.example.android.guesstheword.databinding.GameFragmentBinding
import timber.log.Timber

class GameFragment : Fragment() {

private lateinit var binding: GameFragmentBinding

private lateinit var gameViewModel: GameViewModel



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
    )

    Timber.i("onCreateView  GameFragment called")
    gameViewModel = ViewModelProvider(this).get(GameViewModel::class.java)
    Timber.i("ViewModelProvider is called")

    binding.correctButton.setOnClickListener {
        gameViewModel.onCorrect()
        updateScoreText()
        updateWordText()
    }
    binding.skipButton.setOnClickListener {
        gameViewModel.onSkip()
        updateScoreText()
        updateWordText()
    }
    updateScoreText()
    updateWordText()
    return binding.root

}

/**
 * Called when the game is finished
 */
fun gameFinished() {
    val action = GameFragmentDirections.actionGameToScore(gameViewModel.score)
    findNavController(this).navigate(action)
}

/** Methods for updating the UI **/

private fun updateWordText() {
    binding.wordText.text = gameViewModel.word
}

private fun updateScoreText() {
    binding.scoreText.text = gameViewModel.score.toString()
}

override fun onDestroyView() {
    super.onDestroyView()
    Timber.i("onDestroyView GameFragment called")
}
}
我的ViewModel类

package com.example.android.guesstheword.screens.game

import androidx.lifecycle.ViewModel
import timber.log.Timber

var word = ""
var score = 0

private lateinit var wordList: MutableList<String>

class GameViewModel: ViewModel() {
init {
    Timber.i("GameViewModel is created")
    resetList()
    nextWord()
}

override fun onCleared() {
    super.onCleared()
    Timber.i("GameViewModel is cleared")
}
/**
 * Resets the list of words and randomizes the order
 */


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()) {
        //gameFinished()
    } else {
        word = wordList.removeAt(0)
    }
}
/** Methods for buttons presses **/

fun onSkip() {
    score--
    nextWord()
}

fun onCorrect() {
    score++
    nextWord()
}
}
我在哪里弄糟的？

[我正在学习有关用Kotlin开发Android应用程序的UDACITY免费课程，而我实际上是在本课程的Viewmodel / MVVM部分，即实现Viewmodel类以更好地分离...

Answer 1

您尝试访问的变量不在同一范围内：