状態の保持と永続ストレージ
コレクションでコンテンツを整理
必要に応じて、コンテンツの保存と分類を行います。
Jetpack Compose
Jetpack Compose では通常、UI の状態の管理には
remember
および
rememberSaveable
。
しばらく
rememberSaveable
構成変更後も自動的に状態を保持します。組み込みの
使用できるオブジェクトは、プリミティブ データ型と、
Parcelable
または
Serializable
。
複雑なネストされた構造とプロパティを含む可能性がある Brush
などのカスタム オブジェクトの場合、明示的なシリアル化とシリアル化解除のメカニズムが必要です。カスタムの状態セーバーは
役立ちます。カスタム
Saver
:
Brush
オブジェクト。
上の例で示した例の brushStateSaver
を使用して、
Converters
クラスを使用すると、
構成が変更されてもブラシの基本属性が保持される
発生しません
fun brushStateSaver(converters: Converters): Saver<MutableState<Brush>, String> = Saver(
save = { state ->
converters.brushToString(state.value)
},
restore = { jsonString ->
val brush = converters.stringToBrush(jsonString)
mutableStateOf(brush)
}
)
その後、カスタムの
Saver
~
以下のようにして、ユーザーが選択したブラシの状態を保持します。
val converters = Converters()
val currentBrush = rememberSaveable(saver = brushStateSaver(converters)) { mutableStateOf(defaultBrush) }
永続ストレージ
ドキュメントの保存、読み込み、リアルタイムのコラボレーションなどの機能を有効にするには、ストロークと関連データをシリアル化された形式で保存します。Ink API の場合は、手動でシリアル化とシリアル化解除を行う必要があります。
ストロークを正確に復元するには、その Brush
と [StrokeInputBatch
] を保存します。
基本的なシリアル化
Ink ライブラリ オブジェクトをミラーリングするシリアル化オブジェクト構造を定義します。
Gson、Moshi、Protobuf などの任意のフレームワークを使用してシリアル化されたデータをエンコードし、圧縮を使用して最適化します。
data class SerializedStroke(
val inputs: SerializedStrokeInputBatch,
val brush: SerializedBrush
)
data class SerializedBrush(
val size: Float,
val color: Long,
val epsilon: Float,
val stockBrush: SerializedStockBrush
)
enum class SerializedStockBrush {
MARKER_V1,
PRESSURE_PEN_V1,
HIGHLIGHTER_V1
}
data class SerializedStrokeInputBatch(
val toolType: SerializedToolType,
val strokeUnitLengthCm: Float,
val inputs: List<SerializedStrokeInput>
)
data class SerializedStrokeInput(
val x: Float,
val y: Float,
val timeMillis: Float,
val pressure: Float,
val tiltRadians: Float,
val orientationRadians: Float,
val strokeUnitLengthCm: Float
)
enum class SerializedToolType {
STYLUS,
TOUCH,
MOUSE,
UNKNOWN
}
class Converters {
private val gson: Gson = GsonBuilder().create()
companion object {
private val stockBrushToEnumValues =
mapOf(
StockBrushes.markerV1 to SerializedStockBrush.MARKER_V1,
StockBrushes.pressurePenV1 to SerializedStockBrush.PRESSURE_PEN_V1,
StockBrushes.highlighterV1 to SerializedStockBrush.HIGHLIGHTER_V1,
)
private val enumToStockBrush =
stockBrushToEnumValues.entries.associate { (key, value) -> value to key }
}
private fun serializeBrush(brush: Brush): SerializedBrush {
return SerializedBrush(
size = brush.size,
color = brush.colorLong,
epsilon = brush.epsilon,
stockBrush = stockBrushToEnumValues[brush.family] ?: SerializedStockBrush.MARKER_V1,
)
}
private fun serializeStrokeInputBatch(inputs: StrokeInputBatch): SerializedStrokeInputBatch {
val serializedInputs = mutableListOf<SerializedStrokeInput>()
val scratchInput = StrokeInput()
for (i in 0 until inputs.size) {
inputs.populate(i, scratchInput)
serializedInputs.add(
SerializedStrokeInput(
x = scratchInput.x,
y = scratchInput.y,
timeMillis = scratchInput.elapsedTimeMillis.toFloat(),
pressure = scratchInput.pressure,
tiltRadians = scratchInput.tiltRadians,
orientationRadians = scratchInput.orientationRadians,
strokeUnitLengthCm = scratchInput.strokeUnitLengthCm,
)
)
}
val toolType =
when (inputs.getToolType()) {
InputToolType.STYLUS -> SerializedToolType.STYLUS
InputToolType.TOUCH -> SerializedToolType.TOUCH
InputToolType.MOUSE -> SerializedToolType.MOUSE
else -> SerializedToolType.UNKNOWN
}
return SerializedStrokeInputBatch(
toolType = toolType,
strokeUnitLengthCm = inputs.getStrokeUnitLengthCm(),
inputs = serializedInputs,
)
}
private fun deserializeStroke(serializedStroke: SerializedStroke): Stroke? {
val inputs = deserializeStrokeInputBatch(serializedStroke.inputs) ?: return null
val brush = deserializeBrush(serializedStroke.brush) ?: return null
return Stroke(brush = brush, inputs = inputs)
}
private fun deserializeBrush(serializedBrush: SerializedBrush): Brush {
val stockBrushFamily = enumToStockBrush[serializedBrush.stockBrush] ?: StockBrushes.markerV1
return Brush.createWithColorLong(
family = stockBrushFamily,
colorLong = serializedBrush.color,
size = serializedBrush.size,
epsilon = serializedBrush.epsilon,
)
}
private fun deserializeStrokeInputBatch(
serializedBatch: SerializedStrokeInputBatch
): StrokeInputBatch {
val toolType =
when (serializedBatch.toolType) {
SerializedToolType.STYLUS -> InputToolType.STYLUS
SerializedToolType.TOUCH -> InputToolType.TOUCH
SerializedToolType.MOUSE -> InputToolType.MOUSE
else -> InputToolType.UNKNOWN
}
val batch = MutableStrokeInputBatch()
serializedBatch.inputs.forEach { input ->
batch.addOrThrow(
type = toolType,
x = input.x,
y = input.y,
elapsedTimeMillis = input.timeMillis.toLong(),
pressure = input.pressure,
tiltRadians = input.tiltRadians,
orientationRadians = input.orientationRadians,
)
}
return batch
}
fun serializeStrokeToEntity(stroke: Stroke): StrokeEntity {
val serializedBrush = serializeBrush(stroke.brush)
val serializedInputs = serializeStrokeInputBatch(stroke.inputs)
return StrokeEntity(
brushSize = serializedBrush.size,
brushColor = serializedBrush.color,
brushEpsilon = serializedBrush.epsilon,
stockBrush = serializedBrush.stockBrush,
strokeInputs = gson.toJson(serializedInputs),
)
}
fun deserializeEntityToStroke(entity: StrokeEntity): Stroke {
val serializedBrush =
SerializedBrush(
size = entity.brushSize,
color = entity.brushColor,
epsilon = entity.brushEpsilon,
stockBrush = entity.stockBrush,
)
val serializedInputs =
gson.fromJson(entity.strokeInputs, SerializedStrokeInputBatch::class.java)
val brush = deserializeBrush(serializedBrush)
val inputs = deserializeStrokeInputBatch(serializedInputs)
return Stroke(brush = brush, inputs = inputs)
}
fun brushToString(brush: Brush): String {
val serializedBrush = serializeBrush(brush)
return gson.toJson(serializedBrush)
}
fun stringToBrush(jsonString: String): Brush {
val serializedBrush = gson.fromJson(jsonString, SerializedBrush::class.java)
return deserializeBrush(serializedBrush)
}
}
このページのコンテンツやコードサンプルは、コンテンツ ライセンスに記載のライセンスに従います。Java および OpenJDK は Oracle および関連会社の商標または登録商標です。
最終更新日 2025-07-27 UTC。
[[["わかりやすい","easyToUnderstand","thumb-up"],["問題の解決に役立った","solvedMyProblem","thumb-up"],["その他","otherUp","thumb-up"]],[["必要な情報がない","missingTheInformationINeed","thumb-down"],["複雑すぎる / 手順が多すぎる","tooComplicatedTooManySteps","thumb-down"],["最新ではない","outOfDate","thumb-down"],["翻訳に関する問題","translationIssue","thumb-down"],["サンプル / コードに問題がある","samplesCodeIssue","thumb-down"],["その他","otherDown","thumb-down"]],["最終更新日 2025-07-27 UTC。"],[],[],null,["# State preservation and persistent storage\n\nJetpack Compose\n---------------\n\nIn Jetpack Compose, UI state is typically managed using\n[`remember`](/reference/kotlin/androidx/compose/runtime/package-summary#remember(kotlin.Function0))\nand\n[`rememberSaveable`](/reference/kotlin/androidx/compose/runtime/saveable/package-summary#rememberSaveable(kotlin.Array,androidx.compose.runtime.saveable.Saver,kotlin.String,kotlin.Function0)).\nWhile\n[`rememberSaveable`](/reference/kotlin/androidx/compose/runtime/saveable/package-summary#rememberSaveable(kotlin.Array,androidx.compose.runtime.saveable.Saver,kotlin.String,kotlin.Function0))\noffers automatic state preservation across configuration changes, its built-in\ncapabilities are limited to primitive data types and objects that implement\n[`Parcelable`](/reference/kotlin/android/os/Parcelable) or\n[`Serializable`](/reference/java/io/Serializable).\n\nFor custom objects such as\n[`Brush`](/reference/kotlin/androidx/ink/brush/Brush), which may encompass\nintricate nested structures and properties, explicit serialization and\ndeserialization mechanisms are necessary. This is where a custom state saver\nbecomes useful. By defining a custom\n[`Saver`](/reference/kotlin/androidx/compose/runtime/saveable/Saver) for\nthe `Brush` object, as\ndemonstrated in the provided example with `brushStateSaver`using the example\n`Converters`class, you can guarantee the\npreservation of the brush's essential attributes even when configuration changes\noccur. \n\n fun brushStateSaver(converters: Converters): Saver\u003cMutableState\u003cBrush\u003e, String\u003e = Saver(\n save = { state -\u003e\n converters.brushToString(state.value)\n },\n restore = { jsonString -\u003e\n val brush = converters.stringToBrush(jsonString)\n mutableStateOf(brush)\n }\n )\n\nYou can then use the custom\n[`Saver`](/reference/kotlin/androidx/compose/runtime/saveable/Saver) to\npreserve a user's selected brush state like so: \n\n val converters = Converters()\n val currentBrush = rememberSaveable(saver = brushStateSaver(converters)) { mutableStateOf(defaultBrush) }\n\n### Persistent storage\n\nTo enable features such as document saving, loading, and potential real-time\ncollaboration, store strokes and associated data in a serialized format. For the\nInk API, manual serialization and deserialization are necessary.\n\nTo accurately restore a stroke, save its`Brush` and \\[`StrokeInputBatch`\\].\n\n- [**`Brush`**](/reference/kotlin/androidx/ink/brush/Brush): Includes numeric fields (size, epsilon), color, and [`BrushFamily`](/reference/kotlin/androidx/ink/brush/BrushFamily).\n- [**`StrokeInputBatch`**](/reference/kotlin/androidx/ink/strokes/StrokeInputBatch): Essentially a list of input points with numeric fields.\n\n#### Basic serialization\n\nDefine a serialization object structure that mirrors the Ink library objects.\n\nEncode the serialized data using your preferred framework like Gson, Moshi,\nProtobuf, and others, and use compression for optimization. \n\n data class SerializedStroke(\n val inputs: SerializedStrokeInputBatch,\n val brush: SerializedBrush\n )\n\n data class SerializedBrush(\n val size: Float,\n val color: Long,\n val epsilon: Float,\n val stockBrush: SerializedStockBrush\n )\n\n enum class SerializedStockBrush {\n MARKER_V1,\n PRESSURE_PEN_V1,\n HIGHLIGHTER_V1\n }\n\n data class SerializedStrokeInputBatch(\n val toolType: SerializedToolType,\n val strokeUnitLengthCm: Float,\n val inputs: List\u003cSerializedStrokeInput\u003e\n )\n\n data class SerializedStrokeInput(\n val x: Float,\n val y: Float,\n val timeMillis: Float,\n val pressure: Float,\n val tiltRadians: Float,\n val orientationRadians: Float,\n val strokeUnitLengthCm: Float\n )\n\n enum class SerializedToolType {\n STYLUS,\n TOUCH,\n MOUSE,\n UNKNOWN\n }\n\n class Converters {\n\n private val gson: Gson = GsonBuilder().create()\n\n companion object {\n private val stockBrushToEnumValues =\n mapOf(\n StockBrushes.markerV1 to SerializedStockBrush.MARKER_V1,\n StockBrushes.pressurePenV1 to SerializedStockBrush.PRESSURE_PEN_V1,\n StockBrushes.highlighterV1 to SerializedStockBrush.HIGHLIGHTER_V1,\n )\n\n private val enumToStockBrush =\n stockBrushToEnumValues.entries.associate { (key, value) -\u003e value to key }\n }\n\n private fun serializeBrush(brush: Brush): SerializedBrush {\n return SerializedBrush(\n size = brush.size,\n color = brush.colorLong,\n epsilon = brush.epsilon,\n stockBrush = stockBrushToEnumValues[brush.family] ?: SerializedStockBrush.MARKER_V1,\n )\n }\n\n private fun serializeStrokeInputBatch(inputs: StrokeInputBatch): SerializedStrokeInputBatch {\n val serializedInputs = mutableListOf\u003cSerializedStrokeInput\u003e()\n val scratchInput = StrokeInput()\n\n for (i in 0 until inputs.size) {\n inputs.populate(i, scratchInput)\n serializedInputs.add(\n SerializedStrokeInput(\n x = scratchInput.x,\n y = scratchInput.y,\n timeMillis = scratchInput.elapsedTimeMillis.toFloat(),\n pressure = scratchInput.pressure,\n tiltRadians = scratchInput.tiltRadians,\n orientationRadians = scratchInput.orientationRadians,\n strokeUnitLengthCm = scratchInput.strokeUnitLengthCm,\n )\n )\n }\n\n val toolType =\n when (inputs.getToolType()) {\n InputToolType.STYLUS -\u003e SerializedToolType.STYLUS\n InputToolType.TOUCH -\u003e SerializedToolType.TOUCH\n InputToolType.MOUSE -\u003e SerializedToolType.MOUSE\n else -\u003e SerializedToolType.UNKNOWN\n }\n\n return SerializedStrokeInputBatch(\n toolType = toolType,\n strokeUnitLengthCm = inputs.getStrokeUnitLengthCm(),\n inputs = serializedInputs,\n )\n }\n\n private fun deserializeStroke(serializedStroke: SerializedStroke): Stroke? {\n val inputs = deserializeStrokeInputBatch(serializedStroke.inputs) ?: return null\n val brush = deserializeBrush(serializedStroke.brush) ?: return null\n return Stroke(brush = brush, inputs = inputs)\n }\n\n private fun deserializeBrush(serializedBrush: SerializedBrush): Brush {\n val stockBrushFamily = enumToStockBrush[serializedBrush.stockBrush] ?: StockBrushes.markerV1\n\n return Brush.createWithColorLong(\n family = stockBrushFamily,\n colorLong = serializedBrush.color,\n size = serializedBrush.size,\n epsilon = serializedBrush.epsilon,\n )\n }\n\n private fun deserializeStrokeInputBatch(\n serializedBatch: SerializedStrokeInputBatch\n ): StrokeInputBatch {\n val toolType =\n when (serializedBatch.toolType) {\n SerializedToolType.STYLUS -\u003e InputToolType.STYLUS\n SerializedToolType.TOUCH -\u003e InputToolType.TOUCH\n SerializedToolType.MOUSE -\u003e InputToolType.MOUSE\n else -\u003e InputToolType.UNKNOWN\n }\n\n val batch = MutableStrokeInputBatch()\n\n serializedBatch.inputs.forEach { input -\u003e\n batch.addOrThrow(\n type = toolType,\n x = input.x,\n y = input.y,\n elapsedTimeMillis = input.timeMillis.toLong(),\n pressure = input.pressure,\n tiltRadians = input.tiltRadians,\n orientationRadians = input.orientationRadians,\n )\n }\n\n return batch\n }\n\n fun serializeStrokeToEntity(stroke: Stroke): StrokeEntity {\n val serializedBrush = serializeBrush(stroke.brush)\n val serializedInputs = serializeStrokeInputBatch(stroke.inputs)\n return StrokeEntity(\n brushSize = serializedBrush.size,\n brushColor = serializedBrush.color,\n brushEpsilon = serializedBrush.epsilon,\n stockBrush = serializedBrush.stockBrush,\n strokeInputs = gson.toJson(serializedInputs),\n )\n }\n\n fun deserializeEntityToStroke(entity: StrokeEntity): Stroke {\n val serializedBrush =\n SerializedBrush(\n size = entity.brushSize,\n color = entity.brushColor,\n epsilon = entity.brushEpsilon,\n stockBrush = entity.stockBrush,\n )\n\n val serializedInputs =\n gson.fromJson(entity.strokeInputs, SerializedStrokeInputBatch::class.java)\n\n val brush = deserializeBrush(serializedBrush)\n val inputs = deserializeStrokeInputBatch(serializedInputs)\n\n return Stroke(brush = brush, inputs = inputs)\n }\n\n fun brushToString(brush: Brush): String {\n val serializedBrush = serializeBrush(brush)\n return gson.toJson(serializedBrush)\n }\n\n fun stringToBrush(jsonString: String): Brush {\n val serializedBrush = gson.fromJson(jsonString, SerializedBrush::class.java)\n return deserializeBrush(serializedBrush)\n }\n\n }"]]