Y.A.M の雑記帳: 12月 2022

ラベルと値が縦に並んでいる表があって、その値の start の位置を合わせたい。

ConstraintLayout で Barrier を使うか、自分で Layout を作ることになる。

Composableの順番で位置を指定する場合

content 内の Composable が「ラベル、値、区切り線、ラベル、値、区切り線、...」のようになっている前提の場合、このようなコードで実現できる。


@Composable
fun LabelValueTable(
    modifier: Modifier = Modifier,
    content: @Composable () -> Unit,
) {
    Layout(
        content = content,
        modifier = modifier
    ) { measurables, constraints ->
        val layoutWidth = constraints.maxWidth

        val labelMeasurables = mutableListOf<Measurable>()
        val valueMeasurables = mutableListOf<Measurable>()
        val dividerMeasurables = mutableListOf<Measurable>()

        measurables.forEachIndexed { index, measurable ->
            when (index % 3) {
                0 -> labelMeasurables.add(measurable)
                1 -> valueMeasurables.add(measurable)
                2 -> dividerMeasurables.add(measurable)
            }
        }

        val constraintsForLabel = constraints.copy(minWidth = 0, minHeight = 0)
        val labelPlaceables = labelMeasurables.map { it.measure(constraintsForLabel) }
        val widthOfLabel = labelPlaceables.maxOf { it.width }

        val constraintsForValue = constraintsForLabel.copy(maxWidth = layoutWidth - widthOfLabel)
        val valuePlaceables = valueMeasurables.map { it.measure(constraintsForValue) }

        val dividerPlaceables = dividerMeasurables.map { it.measure(constraintsForLabel) }

        val heights = labelPlaceables.mapIndexed { index, labelPlaceable ->
            val valuePlaceable = valuePlaceables.getOrNull(index)
            max(labelPlaceable.height, valuePlaceable?.height ?: 0)
        }

        layout(
            width = constraints.maxWidth,
            height = max(
                heights.sum() + dividerPlaceables.sumOf { it.height },
                constraints.minHeight
            ),
        ) {
            var top = 0

            labelPlaceables.forEachIndexed { index, labelPlaceable ->
                val rowHeight = heights[index]

                labelPlaceable.placeRelative(
                    x = 0,
                    y = top + (rowHeight - labelPlaceable.height) / 2
                )

                val valuePlaceable = valuePlaceables.getOrNull(index)
                valuePlaceable?.placeRelative(
                    x = widthOfLabel,
                    y = top + (rowHeight - valuePlaceable.height) / 2
                )

                val dividerPlaceable = dividerPlaceables.getOrNull(index)
                dividerPlaceable?.placeRelative(
                    x = 0,
                    y = top + rowHeight
                )

                top += rowHeight + (dividerPlaceable?.height ?: 0)
            }
        }
    }
}

まずラベル部分を measure して、全てのラベルから最大の width（= widthOfLabel）を計算する。

constraints.maxWidth から widthOfLabel を引いた値を maxWidth とした Constrains で値部分を measure する。

あとは、ラベル、値、区切り線を配置する。

値や区切り線に何も表示しないところは Spacer() をおけばいい。


LabelValueTable(
    modifier = modifier.fillMaxWidth()
) {
    Text(
        text = "名前",
        modifier = Modifier.padding(16.dp)
    )
    Text(
        text = "山田 太郎",
        modifier = Modifier.padding(16.dp)
    )
    Divider()

    Text(
        text = "bio",
        modifier = Modifier.padding(16.dp)
    )
    Text(
        text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam",
        modifier = Modifier.padding(16.dp)
    )
    Divider()

    Text(
        text = "label",
        modifier = Modifier.padding(16.dp)
    )
    Column(
        modifier = Modifier.padding(16.dp)
    ) {
        Text(
            text = "headline",
            style = MaterialTheme.typography.bodyLarge,
        )
        Text(
            text = "subtitle",
            style = MaterialTheme.typography.bodySmall,
            color = MaterialTheme.colorScheme.onSurfaceVariant,
        )
    }
    Divider(
        modifier = Modifier.padding(bottom = 24.dp)
    )

    Text(
        text = "生年月日",
        modifier = Modifier.padding(16.dp)
    )
    Row(
        modifier = Modifier.padding(16.dp),
        verticalAlignment = Alignment.CenterVertically,
    ) {
        Text(
            text = "1990-01-01",
            modifier = Modifier.weight(1f)
        )
        IconButton(onClick = { /*TODO*/ }) {
            Icon(imageVector = Icons.Default.Edit, contentDescription = "edit")
        }
    }
    Divider()

    Text(
        text = "性別",
        modifier = Modifier.padding(16.dp)
    )
    Text(
        text = "男性",
        modifier = Modifier.padding(16.dp)
    )
}

ParentDataModifier で位置を指定する場合

ParentDataModifier を使って Cell の位置を指定する場合、このようなコードで実現できる。


@Composable
fun LabelValueTable(
    modifier: Modifier = Modifier,
    content: @Composable LabelValueTableScope.() -> Unit,
) {
    Layout(
        content = { LabelValueTableScopeInstance.content() },
        modifier = modifier
    ) { measurables, constraints ->
        val layoutWidth = constraints.maxWidth

        val labelMeasurables = mutableListOf<Measurable>()
        val valueMeasurables = mutableListOf<Measurable>()
        val dividerMeasurables = mutableListOf<Measurable>()

        measurables.forEach { measurable ->
            when (measurable.parentData) {
                is LabelIndex -> labelMeasurables.add(measurable)
                is ValueIndex -> valueMeasurables.add(measurable)
                is DividerIndex -> dividerMeasurables.add(measurable)
            }
        }

        val map = mutableMapOf<Int, Triple<Placeable?, Placeable?, Placeable?>>()

        val constraintsForLabel = constraints.copy(minWidth = 0, minHeight = 0)
        val labelPlaceables = labelMeasurables.map { it.measure(constraintsForLabel) }
        val widthOfLabel = labelPlaceables.maxOf { it.width }
        labelMeasurables.forEachIndexed { index, measurable ->
            val columnIndex = (measurable.parentData as LabelIndex).columnIndex
            map[columnIndex] = Triple(labelPlaceables[index], null, null)
        }

        val constraintsForValue = constraintsForLabel.copy(maxWidth = layoutWidth - widthOfLabel)
        val valuePlaceables = valueMeasurables.map { it.measure(constraintsForValue) }
        valueMeasurables.forEachIndexed { index, measurable ->
            val columnIndex = (measurable.parentData as ValueIndex).columnIndex
            map[columnIndex] = map.getOrDefault(columnIndex, Triple(null, null, null))
                .copy(second = valuePlaceables[index])
        }

        val dividerPlaceables = dividerMeasurables.map { it.measure(constraintsForLabel) }
        dividerMeasurables.forEachIndexed { index, measurable ->
            val columnIndex = (measurable.parentData as DividerIndex).columnIndex
            map[columnIndex] = map.getOrDefault(columnIndex, Triple(null, null, null))
                .copy(third = dividerPlaceables[index])
        }

        val list = map.toList()
            .sortedBy { it.first }
            .map { it.second }

        val heights = list.map {
            max(it.first?.height ?: 0, it.second?.height ?: 0)
        }

        layout(
            width = constraints.maxWidth,
            height = max(
                heights.sum() + dividerPlaceables.sumOf { it.height },
                constraints.minHeight
            ),
        ) {
            var top = 0

            list.forEachIndexed { index, triple ->
                val (labelPlaceable, valuePlaceable, dividerPlaceable) = triple
                val rowHeight = heights[index]

                labelPlaceable?.placeRelative(
                    x = 0,
                    y = top + (rowHeight - labelPlaceable.height) / 2
                )

                valuePlaceable?.placeRelative(
                    x = widthOfLabel,
                    y = top + (rowHeight - valuePlaceable.height) / 2
                )

                dividerPlaceable?.placeRelative(
                    x = 0,
                    y = top + rowHeight
                )

                top += rowHeight + (dividerPlaceable?.height ?: 0)
            }
        }
    }
}


@Immutable
interface LabelValueTableScope {
    @Stable
    fun Modifier.label(columnIndex: Int): Modifier

    @Stable
    fun Modifier.value(columnIndex: Int): Modifier

    @Stable
    fun Modifier.divider(columnIndex: Int): Modifier
}

internal object LabelValueTableScopeInstance : LabelValueTableScope {

    @Stable
    override fun Modifier.label(columnIndex: Int): Modifier {
        return this.then(LabelIndex(columnIndex))
    }

    @Stable
    override fun Modifier.value(columnIndex: Int): Modifier {
        return this.then(ValueIndex(columnIndex))
    }

    @Stable
    override fun Modifier.divider(columnIndex: Int): Modifier {
        return this.then(DividerIndex(columnIndex))
    }
}

@Immutable
private data class LabelIndex(val columnIndex: Int) : ParentDataModifier {
    override fun Density.modifyParentData(parentData: Any?): Any? {
        return this@LabelIndex
    }
}

@Immutable
private data class ValueIndex(val columnIndex: Int) : ParentDataModifier {
    override fun Density.modifyParentData(parentData: Any?): Any? {
        return this@ValueIndex
    }
}

@Immutable
private data class DividerIndex(val columnIndex: Int) : ParentDataModifier {
    override fun Density.modifyParentData(parentData: Any?): Any? {
        return this@DividerIndex
    }
}

measurable.parentData からラベル、値、区切り線のどれで、column index が何かを取得する。

measure と配置部分でやっていることは同じ。

使う側では Modifier.label(), Modifier.value(), Modifier.divider() を使って位置を指定する。


LabelValueTable(
    modifier = modifier.fillMaxWidth()
) {
    Text(
        text = "名前",
        modifier = Modifier
            .padding(16.dp)
            .label(0)
    )
    Text(
        text = "山田 太郎",
        modifier = Modifier
            .padding(16.dp)
            .value(0)
    )
    Divider(
        modifier = Modifier.divider(0)
    )

    Text(
        text = "bio",
        modifier = Modifier
            .padding(16.dp)
            .label(1)
    )
    Text(
        text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam",
        modifier = Modifier
            .padding(16.dp)
            .value(1)
    )
    Divider(
        modifier = Modifier.divider(1)
    )

    Text(
        text = "label",
        modifier = Modifier
            .padding(16.dp)
            .label(2)
    )
    Column(
        modifier = Modifier
            .padding(16.dp)
            .value(2)
    ) {
        Text(
            text = "headline",
            style = MaterialTheme.typography.bodyLarge,
        )
        Text(
            text = "subtitle",
            style = MaterialTheme.typography.bodySmall,
            color = MaterialTheme.colorScheme.onSurfaceVariant,
        )
    }
    Divider(
        modifier = Modifier
            .padding(bottom = 24.dp)
            .divider(2)
    )

    Text(
        text = "生年月日",
        modifier = Modifier
            .padding(16.dp)
            .label(3)
    )
    Row(
        verticalAlignment = Alignment.CenterVertically,
        modifier = Modifier
            .padding(16.dp)
            .value(3),
    ) {
        Text(
            text = "1990-01-01",
            modifier = Modifier.weight(1f)
        )
        IconButton(onClick = { /*TODO*/ }) {
            Icon(imageVector = Icons.Default.Edit, contentDescription = "edit")
        }
    }
    Divider(
        modifier = Modifier.divider(3)
    )

    Text(
        text = "性別",
        modifier = Modifier
            .padding(16.dp)
            .label(4)
    )
    Text(
        text = "男性",
        modifier = Modifier
            .padding(16.dp)
            .value(4)
    )
}

ParentDataModifier は、親の Layout にデータを提供するための Modifier です。
ParentDataModifier の Density.modifyParentData() で返したデータが IntrinsicMeasurable.parentData に格納されます。

Measureable が IntrinsicMeasurable を実装しているので、MeasurePolicy の MeasureScope.measure() でこのデータを利用できます。


Layout(
    content = content,
    modifier = modifier
) { measurables, constraints ->
    measurables.forEach {
        val parentData = measurable.parentData

        ...
    }


    ...
}

ParentDataModifier interface を実装している Modifier として

LayoutId
BoxChildData
LayoutWeightImpl
HorizontalAlignModifier
VerticalAlignModifier
SiblingsAlignedModifier

などがあります。

この中で LayoutId は自分の Layout でも使うことができます。


Layout(
    content = {
        Icon(
            imageVector = Icons.Default.Home,
            contentDescription = "home",
            modifier = Modifier.layoutId("icon")
        )
        Text(
            text = "home",
            modifier = Modifier.layoutId("text")
        )
    },
    modifier = modifier
) { measurables, constraints ->
    
    val iconMeasurable = measurables.first { it.layoutId == "icon" }
    val textMeasurable = measurables.first { it.layoutId == "text" }
    
    ...
}

Modifier.layoutId() は LayoutId を適用した Modifier を返すメソッドです。


@Stable
fun Modifier.layoutId(layoutId: Any) = this.then(
    LayoutId(
        layoutId = layoutId,
        inspectorInfo = debugInspectorInfo {
            name = "layoutId"
            value = layoutId
        }
    )
)

LayoutId は ParentDataModifier と LayoutIdParentData を実装した Modifier で、Density.modifyParentData() では LayoutId 自身を返します。


@Immutable
private class LayoutId(
    override val layoutId: Any,
    inspectorInfo: InspectorInfo.() -> Unit
) : ParentDataModifier, LayoutIdParentData, InspectorValueInfo(inspectorInfo) {
    override fun Density.modifyParentData(parentData: Any?): Any? {
        return this@LayoutId
    }

    ...
}
  
interface LayoutIdParentData {
    val layoutId: Any
}

Measurable.layoutId は parentData から Modifier.layoutId() で渡した layoutId を取得する便利メソッドです。


val Measurable.layoutId: Any?
    get() = (parentData as? LayoutIdParentData)?.layoutId

ParentDataModifier を実装した独自 Modifier を用意することができます。


@Immutable
interface MyLayoutScope {
    @Stable
    fun Modifier.myLayoutData(index: Int): Modifier
}

internal object MyLayoutScopeInstance : MyLayoutScope {

    @Stable
    override fun Modifier.myLayoutData(index: Int): Modifier {
        return this.then(MyLayoutData(index = index))
    }
}

@Immutable
private data class MyLayoutData(val index: Int) : ParentDataModifier {
    override fun Density.modifyParentData(parentData: Any?): Any? {
        return this@MyLayoutData
    }
}
  
val Measurable.index: Int?
    get() = (parentData as? MyLayoutData)?.index

Y.A.M の雑記帳

2022年12月7日水曜日

ラベルと値が縦に並んでいて、値部分の start が揃っている Composable を作る

Composableの順番で位置を指定する場合

ParentDataModifier で位置を指定する場合

2022年12月6日火曜日

ParentDataModifier