在 Android 中保存和检索数据

Question

private var highScore: Int = 0
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding = DataBindingUtil.setContentView(this, R.layout.activity_game)
    loadData()
    playGame()
}
override fun onDestroy() {
    super.onDestroy()
    saveData()
}
private fun saveData(){
    val sharedPreferences = getSharedPreferences("sharedPrefs", Context.MODE_PRIVATE)
    val editor = sharedPreferences.edit()
    editor.apply{
        putInt("INTEGER_KEY", highScore)
    }.apply()
}
private fun loadData(){
    val sharedPreferences = getSharedPreferences("sharedPrefs", Context.MODE_PRIVATE)
    val savedInt = sharedPreferences.getInt("INTEGER_KEY", 0)
    highScore = savedInt
    binding.highScore.text = "Highscore: $savedInt"
}

I've made a simple game and I need to store the the highscore value and retrieve the value when the app is relaunched. I've tried to use sharedPreferences in the given code. But the highscore data is lost when I close the app and relaunch it. How can I save and retrieve the value? PS: The highscore value is saved/retrieved properly when running the app in Android Studio's emulator. But it doesn't work when I run the app on my phone. It resets to 0 every time I relaunch it.

Answer 1

you are trying to save, when the app is destroyed. This might work sometimes, when onDestroy is actually called, but that does not happen for sure.

Apply is saving the data asynchronous to the disk, which won't happen as you are trying to do it when the app is destroyed. You have to use commit instead of apply to save the data synchronous.

I would recommend to save the data at another point of your app instead of in onDestroy, as this won't be called every time the app is closed/killed.