kotlin pref convient

SharedPreferenceDelegate.kt

private class SharedPreferenceDelegate<T>(
        private val context: Context,
        private val defaultValue: T,
        private val getter: SharedPreferences.(String, T) -> T,
        private val setter: Editor.(String, T) -> Editor,
        private val key: String
) : ReadWriteProperty<Any, T> {
 
    private val safeContext: Context by lazyFast { context.safeContext() }
 
    private val sharedPreferences: SharedPreferences by lazyFast {
        PreferenceManager.getDefaultSharedPreferences(safeContext)
    }
 
    override fun getValue(thisRef: Any, property: KProperty<*>) =
            sharedPreferences
                    .getter(key, defaultValue)
 
    override fun setValue(thisRef: Any, property: KProperty<*>, value: T) =
            sharedPreferences
                    .edit()
                    .setter(key, value)
                    .apply()
}
 
@Suppress("UNCHECKED_CAST")
fun <T> bindSharedPreference(context: Context, key: String, defaultValue: T): ReadWriteProperty<Any, T> =
        when (defaultValue) {
            is Boolean ->
                SharedPreferenceDelegate(context, defaultValue, SharedPreferences::getBoolean, Editor::putBoolean, key)
            is Int ->
                SharedPreferenceDelegate(context, defaultValue, SharedPreferences::getInt, Editor::putInt, key)
            is Long ->
                SharedPreferenceDelegate(context, defaultValue, SharedPreferences::getLong, Editor::putLong, key)
            is Float ->
                SharedPreferenceDelegate(context, defaultValue, SharedPreferences::getFloat, Editor::putFloat, key)
            is String ->
                SharedPreferenceDelegate(context, defaultValue, SharedPreferences::getString, Editor::putString, key)
            else -> throw IllegalArgumentException()
        } as ReadWriteProperty<Any, T>