2020/10/25: kotlinx.serialization 1.0.0 の変更に対応しました
Kotlin の委譲プロパティを使って、Android SharedPreferences を無駄なくシンプルに扱えるようにします。
以下の記事の kotlinx.serialization 版です。説明は以下の記事を参照してください。
SharedPreferencesExtension.kt
import android.content.SharedPreferences
import kotlinx.serialization.KSerializer
import kotlinx.serialization.decodeFromString
import kotlinx.serialization.encodeToString
import kotlinx.serialization.json.Json
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty
/**
* Boolean Read Write Delegate
*/
fun SharedPreferences.boolean(defaultValue: Boolean = false, key: String? = null): ReadWriteProperty<Any, Boolean> =
delegate(defaultValue, key, SharedPreferences::getBoolean, SharedPreferences.Editor::putBoolean)
/**
* Nullable Boolean Read Write Delegate
*/
fun SharedPreferences.nullableBoolean(key: String? = null): ReadWriteProperty<Any, Boolean?> =
nullableDelegate(false, key, SharedPreferences::getBoolean, SharedPreferences.Editor::putBoolean)
/**
* Float Read Write Delegate
*/
fun SharedPreferences.float(defaultValue: Float = 0f, key: String? = null): ReadWriteProperty<Any, Float> =
delegate(defaultValue, key, SharedPreferences::getFloat, SharedPreferences.Editor::putFloat)
/**
* Nullable Float Read Write Delegate
*/
fun SharedPreferences.nullableFloat(key: String? = null): ReadWriteProperty<Any, Float?> =
nullableDelegate(0f, key, SharedPreferences::getFloat, SharedPreferences.Editor::putFloat)
/**
* Int Read Write Delegate
*/
fun SharedPreferences.int(defaultValue: Int = 0, key: String? = null): ReadWriteProperty<Any, Int> =
delegate(defaultValue, key, SharedPreferences::getInt, SharedPreferences.Editor::putInt)
/**
* Nullable Int Read Write Delegate
*/
fun SharedPreferences.nullableInt(key: String? = null): ReadWriteProperty<Any, Int?> =
nullableDelegate(0, key, SharedPreferences::getInt, SharedPreferences.Editor::putInt)
/**
* Long Read Write Delegate
*/
fun SharedPreferences.long(defaultValue: Long = 0, key: String? = null): ReadWriteProperty<Any, Long> =
delegate(defaultValue, key, SharedPreferences::getLong, SharedPreferences.Editor::putLong)
/**
* Nullable Long Read Write Delegate
*/
fun SharedPreferences.nullableLong(key: String? = null): ReadWriteProperty<Any, Long?> =
nullableDelegate(0, key, SharedPreferences::getLong, SharedPreferences.Editor::putLong)
/**
* String Read Write Delegate
*/
fun SharedPreferences.string(defaultValue: String = "", key: String? = null): ReadWriteProperty<Any, String> =
delegate(defaultValue, key, SharedPreferences::getString, SharedPreferences.Editor::putString)
/**
* Nullable String Read Write Delegate
*/
fun SharedPreferences.nullableString(key: String? = null): ReadWriteProperty<Any, String?> =
nullableDelegate("", key, SharedPreferences::getString, SharedPreferences.Editor::putString)
/**
* Enum Read Write Delegate
*/
fun <T : Enum<T>> SharedPreferences.enum(valueOf: (String) -> T, defaultValue: Lazy<T>, key: String? = null) =
object : ReadWriteProperty<Any, T> {
override fun getValue(thisRef: Any, property: KProperty<*>): T {
return getString(key ?: property.name, null)?.let { valueOf(it) } ?: defaultValue.value
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T) {
edit().putString(key ?: property.name, value.name).apply()
}
}
/**
* Nullable Enum Read Write Delegate
*/
fun <T : Enum<T>> SharedPreferences.nullableEnum(valueOf: (String) -> T, key: String? = null) =
object : ReadWriteProperty<Any, T?> {
override fun getValue(thisRef: Any, property: KProperty<*>): T? {
return getString(key ?: property.name, null)?.let { valueOf(it) }
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T?) {
edit().putString(key ?: property.name, value?.name).apply()
}
}
/**
* Kotlinx.Serialization Json String Read Write Delegate
*/
inline fun <reified T : Any> SharedPreferences.json(json: Json, defaultValue: Lazy<T>, key: String? = null) =
object : ReadWriteProperty<Any, T> {
override fun getValue(thisRef: Any, property: KProperty<*>): T {
return getString(key ?: property.name, null)?.let { json.decodeFromString<T>(it) } ?: defaultValue.value
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T) {
edit().putString(key ?: property.name, json.encodeToString(value)).apply()
}
}
/**
* Nullable Kotlinx.Serialization Json String Read Write Delegate
*/
inline fun <reified T : Any> SharedPreferences.nullableJson(json: Json, key: String? = null): ReadWriteProperty<Any, T?> =
object : ReadWriteProperty<Any, T?> {
override fun getValue(thisRef: Any, property: KProperty<*>): T? {
return getString(key ?: property.name, null)?.let { json.decodeFromString(it) }
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T?) {
edit().putString(key ?: property.name, value?.let { json.encodeToString(value) }).apply()
}
}
/**
* Kotlinx.Serialization Json String Read Write Delegate
*/
fun <T : Any> SharedPreferences.json(json: Json, serializer: KSerializer<T>, defaultValue: Lazy<T>, key: String? = null) =
object : ReadWriteProperty<Any, T> {
override fun getValue(thisRef: Any, property: KProperty<*>): T {
return getString(key ?: property.name, null)?.let { json.decodeFromString(serializer, it) } ?: defaultValue.value
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T) {
edit().putString(key ?: property.name, json.encodeToString(serializer, value)).apply()
}
}
/**
* Nullable Kotlinx.Serialization Json String Read Write Delegate
*/
fun <T : Any> SharedPreferences.nullableJson(json: Json, serializer: KSerializer<T>, key: String? = null) =
object : ReadWriteProperty<Any, T?> {
override fun getValue(thisRef: Any, property: KProperty<*>): T? {
return getString(key ?: property.name, null)?.let { json.decodeFromString(serializer, it) }
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T?) {
edit().putString(key ?: property.name, value?.let { json.encodeToString(serializer, it) }).apply()
}
}
private inline fun <T : Any> SharedPreferences.delegate(
defaultValue: T, key: String?,
crossinline getter: SharedPreferences.(key: String, defaultValue: T) -> T?,
crossinline setter: SharedPreferences.Editor.(key: String, value: T) -> SharedPreferences.Editor
) = object : ReadWriteProperty<Any, T> {
override fun getValue(thisRef: Any, property: KProperty<*>) = getter(key ?: property.name, defaultValue) ?: defaultValue
override fun setValue(thisRef: Any, property: KProperty<*>, value: T) =
edit().setter(key ?: property.name, value).apply()
}
private inline fun <T : Any> SharedPreferences.nullableDelegate(
dummy: T, key: String?,
crossinline getter: SharedPreferences.(key: String, defaultValue: T) -> T?,
crossinline setter: SharedPreferences.Editor.(key: String, value: T) -> SharedPreferences.Editor
) = object : ReadWriteProperty<Any, T?> {
override fun getValue(thisRef: Any, property: KProperty<*>): T? {
val target = key ?: property.name
return if (contains(target)) getter(target, dummy) else null
}
override fun setValue(thisRef: Any, property: KProperty<*>, value: T?) {
val target = key ?: property.name
if (value == null) {
edit().remove(target).apply()
} else {
edit().setter(target, value).apply()
}
}
}