mutableStateOf for SharedPreferences

SharedPreferenceDelegates.kt

import android.content.SharedPreferences
import androidx.compose.runtime.MutableState
import androidx.compose.runtime.mutableStateOf
import androidx.core.content.edit
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty

fun SharedPreferences.mutableStateOf(
    key: String,
    defaultValue: String? = null,
): ReadWriteProperty<Any?, String?> = object : ReadWriteProperty<Any?, String?> {
    
    private val cached: MutableState<String?> = mutableStateOf(defaultValue)
    val onSharedPreferenceChangeListener = SharedPreferences.OnSharedPreferenceChangeListener { _, changedKey ->
        if (key == changedKey) {
            cached.value = getString(key, defaultValue)
        }
    }

    init {
        // don't pass onSharedPreferenceChangeListener as an anonymous lambda, it will be GC'd! 
        registerOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener)
    }

    override fun getValue(thisRef: Any?, property: KProperty<*>): String? =
        cached.value ?: getString(key, defaultValue).also { cached.value = it }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: String?) {
        cached.value = value
        edit(commit = false) { 
            putString(key, value)
        }
    }
}