Composable传递ViewModel时实例化失败的原因排查

我跟着Android官方教程实现Unscramble应用，创建了GameViewModel并在GameScreen Composable中用viewModel()注入，但始终遇到**「Failed to instantiate a ViewModel」**错误，预览无法渲染且模拟器中应用持续崩溃。已确认写法和官方示例一致，ViewModel相关依赖也配置完整。

通过排查发现，只要注释掉GameViewModel中resetGame方法内的两行代码，ViewModel就能正常实例化；取消注释任意一行，就会触发实例化失败问题。

相关代码 #

GameScreen Composable #

@Composable
fun GameScreen(
    gameViewModel: GameViewModel = viewModel()
) {
    val gameUiState by gameViewModel.uiState.collectAsState()
    /*
    rest of composable
    */
}

GameViewModel类 #

package com.example.unscramble.ui

import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
import androidx.lifecycle.ViewModel
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asStateFlow
import com.example.unscramble.data.allWords

class GameViewModel : ViewModel() {

    // Game UI state
    private val _uiState = MutableStateFlow(GameUiState())
    var userGuess by mutableStateOf("")
        private set
    // Backing property to avoid state updates from other classes
    val uiState: StateFlow<GameUiState> = _uiState.asStateFlow()
    
    init {
        resetGame()
    }
    
    fun resetGame() {
        usedWords.clear()
        _uiState.value = GameUiState(currentScrambledWord = pickRandomWordAndShuffle())
    }

    private lateinit var currentWord: String

    // Set of words used in the game
    private var usedWords: MutableSet<String> = mutableSetOf()
    
    private fun pickRandomWordAndShuffle(): String {
        // Continue picking up a new random word until you get one that hasn't been used before
        currentWord = allWords.random()
        if (usedWords.contains(currentWord)) {
            return pickRandomWordAndShuffle()
        } else {
            usedWords.add(currentWord)
            return shuffleCurrentWord(currentWord)
        }
    }
    
    private fun shuffleCurrentWord(word: String): String {
        val tempWord = word.toCharArray()
        // Scramble the word
        tempWord.shuffle()
        while (String(tempWord).equals(word)) {
            tempWord.shuffle()
        }
        return String(tempWord)
    }
}

依赖配置 #

dependencies {
    implementation(platform("androidx.compose:compose-bom:2023.08.00"))
    implementation("androidx.activity:activity-compose:1.8.0")
    implementation("androidx.compose.material3:material3")
    implementation("androidx.compose.ui:ui")
    implementation("androidx.compose.ui:ui-graphics")
    implementation("androidx.compose.ui:ui-tooling-preview")
    implementation("androidx.core:core-ktx:1.12.0")
    implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.7.0")
    implementation("androidx.lifecycle:lifecycle-viewmodel-compose:2.7.0")
    implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:2.7.0")
    implementation("androidx.lifecycle:lifecycle-viewmodel-savedstate:2.7.0")
}

核心疑问 #

为什么resetGame()里的usedWords.clear()或者_uiState.value = GameUiState(...)这两行代码会导致ViewModel实例化失败？需要恢复这部分功能，该如何解决？

内容的提问来源于stack exchange，提问作者devel_dizzie