使用方法

object AccountBiz{
    var username by defSP("")
    var mobil:String by defSP("mobil", "")
}

//取值
val name=AccountBiz.username
//存值
AccountBiz.username="aaaaa"

SPUtil實現

const val SPFileName = "Setting"
/**
 * 使用defSP的話key為""在SPUtil中key會賦值成變量名
 * 所以一般用這個
 */
inline fun <reified R, T> R.defSP(default: T) = defSP("", default)
/**
 * 指定key用這個
 */
inline fun <reified R, T> R.defSP(key: String, default: T) = SPUtil(key, default, R::class.java.name)

class SPUtil<T>(val key: String, val defValue: T, val fileName: String = SPFileName) : ReadWriteProperty<Any?, T> {
    val sp by lazy {
        appContext.getSharedPreferences(fileName, Context.MODE_PRIVATE)
    }

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        val temKey = if (key.isEmpty()) property.name else key
        return when (defValue) {
            is String -> sp.getString(temKey, defValue)
            is Boolean -> sp.getBoolean(temKey, defValue)
            is Int -> sp.getInt(temKey, defValue)
            is Float -> sp.getFloat(temKey, defValue)
            is Long -> sp.getLong(temKey, defValue)
            else -> throw IllegalArgumentException("類型錯誤")
        } as T
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        val temKey = if (key.isEmpty()) property.name else key
        with(sp.edit()) {
            when (value) {
                is String -> putString(temKey, value)
                is Boolean -> putBoolean(temKey, value)
                is Int -> putInt(temKey, value)
                is Float -> putFloat(temKey, value)
                is Long -> putLong(temKey, value)
                else -> throw IllegalArgumentException("類型錯誤")
            }
            commit()
        }
    }
}

fun cleanSP(fileName: String = SPFileName) {
    appContext.getSharedPreferences(fileName, Context.MODE_PRIVATE).edit().clear().commit()
}