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Hack RecyclerView.ItemDecoration
@MoyuruAizawa
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MoyuruAizawa
Moyuru Aizawa
Software engineer of CATS Div. CyberAgent Inc.
Previously at Pairs Div. Eureka Inc.
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RecyclerView.ItemDecoration
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‣ An ItemDecoration allows the application to add a special drawing and
layout offset to specific item views
‣ This can be useful for drawing dividers between items, highlights, visual
grouping boundaries and more
RecyclerView.ItemDecoration
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Divider
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override fun getItemOffsets(outRect: Rect, view: View,
parent: RecyclerView, state: RecyclerView.State) {
super.getItemOffsets(outRect, view, parent, state)
if (parent.getChildLayoutPosition(view) < parent.childCount - 1)
outRect.bottom = dividerWidth
}
Divider
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override fun getItemOffsets(outRect: Rect, view: View,
parent: RecyclerView, state: RecyclerView.State) {
super.getItemOffsets(outRect, view, parent, state)
if (parent.getChildLayoutPosition(view) < parent.childCount - 1)
outRect.bottom = dividerWidth
}
Divider
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override fun getItemOffsets(outRect: Rect, view: View,
parent: RecyclerView, state: RecyclerView.State) {
super.getItemOffsets(outRect, view, parent, state)
if (parent.getChildLayoutPosition(view) < parent.childCount - 1)
outRect.bottom = dividerWidth
}
Divider
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
super.onDraw(c, parent, state)
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.forEach {
val left = it.left.toFloat()
val right = it.right.toFloat()
val bottom = it.bottom.toFloat()
c.drawRect(left, bottom, right, bottom + dividerWidth, paint)
}
}
Divider
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
super.onDraw(c, parent, state)
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.forEach {
val left = it.left.toFloat()
val right = it.right.toFloat()
val bottom = it.bottom.toFloat()
c.drawRect(left, bottom, right, bottom + dividerWidth, paint)
}
}
Divider
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
super.onDraw(c, parent, state)
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.forEach {
val left = it.left.toFloat()
val right = it.right.toFloat()
val bottom = it.bottom.toFloat()
c.drawRect(left, bottom, right, bottom + dividerWidth, paint)
}
}
Divider
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Timeline
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Timeline
ItemDecoration
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Timeline
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Timeline
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Timeline
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Timeline
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override fun getItemOffsets(outRect: Rect, view: View,
parent: RecyclerView, state: RecyclerView.State) {
super.getItemOffsets(outRect, view, parent, state)
outRect.left = width
}
Timeline
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.windowed(2, step = 2, partialWindows = true)
.forEach {
val text = "HH:mm"
val top = it.first().top.toFloat() + margin
val centerX = width / 2f
val baseX = centerX - textPaint.measureText(text) / 2
val textBounds = Rect()
.apply { textPaint.getTextBounds(text, 0, text.length - 1, this) }
val baseY = top + textBounds.height()
c.drawText(text, baseX, baseY, textPaint)
c.drawLine(centerX, top + textBounds.height() + margin,
centerX, it.last().bottom.toFloat(), linePaint)
}
}
Timeline
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.windowed(2, step = 2, partialWindows = true)
.forEach {
val text = "HH:mm"
val top = it.first().top.toFloat() + margin
val centerX = width / 2f
val baseX = centerX - textPaint.measureText(text) / 2
val textBounds = Rect()
.apply { textPaint.getTextBounds(text, 0, text.length - 1, this) }
val baseY = top + textBounds.height()
c.drawText(text, baseX, baseY, textPaint)
c.drawLine(centerX, top + textBounds.height() + margin,
centerX, it.last().bottom.toFloat(), linePaint)
}
}
Timeline
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.windowed(2, step = 2, partialWindows = true)
.forEach {
val text = "HH:mm"
val top = it.first().top.toFloat() + margin
val centerX = width / 2f
val baseX = centerX - textPaint.measureText(text) / 2
val textBounds = Rect()
.apply { textPaint.getTextBounds(text, 0, text.length - 1, this) }
val baseY = top + textBounds.height()
c.drawText(text, baseX, baseY, textPaint)
c.drawLine(centerX, top + textBounds.height() + margin,
centerX, it.last().bottom.toFloat(), linePaint)
}
}
Timeline
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.windowed(2, step = 2, partialWindows = true)
.forEach {
val text = "HH:mm"
val top = it.first().top.toFloat() + margin
val centerX = width / 2f
val baseX = centerX - textPaint.measureText(text) / 2
val textBounds = Rect()
.apply { textPaint.getTextBounds(text, 0, text.length - 1, this) }
val baseY = top + textBounds.height()
c.drawText(text, baseX, baseY, textPaint)
c.drawLine(centerX, top + textBounds.height() + margin,
centerX, it.last().bottom.toFloat(), linePaint)
}
}
Timeline
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override fun onDraw(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
(0 until parent.childCount)
.mapNotNull(parent::getChildAt)
.windowed(2, step = 2, partialWindows = true)
.forEach {
val text = "HH:mm"
val top = it.first().top.toFloat() + margin
val centerX = width / 2f
val baseX = centerX - textPaint.measureText(text) / 2
val textBounds = Rect()
.apply { textPaint.getTextBounds(text, 0, text.length - 1, this) }
val baseY = top + textBounds.height()
c.drawText(text, baseX, baseY, textPaint)
c.drawLine(centerX, top + textBounds.height() + margin,
centerX, it.last().bottom.toFloat(), linePaint)
}
}
Timeline
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Timetable
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Timetable
ItemDecoration
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Timetable
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Timetable
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Timetable
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Timetable
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Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val rightView = parent.children.maxBy { it.right } ?: return
val rightColumnNumber = getColumnNumber(rightView.layoutPosition)
val range = …
var offsetX = rightView.right
range.forEach {
c.drawTextAtCenter(getColumnName(it),
Rect(offsetX - columnWidth, 0, offsetX, height), textPaint)
offsetX -= columnWidth
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val rightView = parent.children.maxBy { it.right } ?: return
val rightColumnNumber = getColumnNumber(rightView.layoutPosition)
val range = …
var offsetX = rightView.right
range.forEach {
c.drawTextAtCenter(getColumnName(it),
Rect(offsetX - columnWidth, 0, offsetX, height), textPaint)
offsetX -= columnWidth
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val rightView = parent.children.maxBy { it.right } ?: return
val rightColumnNumber = getColumnNumber(rightView.layoutPosition)
val range = …
var offsetX = rightView.right
range.forEach {
c.drawTextAtCenter(getColumnName(it),
Rect(offsetX - columnWidth, 0, offsetX, height), textPaint)
offsetX -= columnWidth
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val rightView = parent.children.maxBy { it.right } ?: return
val rightColumnNumber = getColumnNumber(rightView.layoutPosition)
val range = …
var offsetX = rightView.right
range.forEach {
c.drawTextAtCenter(getColumnName(it),
Rect(offsetX - columnWidth, 0, offsetX, height), textPaint)
offsetX -= columnWidth
}
}
Timetable
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Timetable
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Timetable
ItemDecoration
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Timetable
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Timetable
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Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val startAtList = (0 until adapter.itemCount).map(this::getStartUnixMillis)
val first = parent.children.minBy { it.top } ?: return
val baseEpochMillis = startAtList.getOrNull(first.layoutPosition) ?: return
startAtList
.filterIndexed { i, startAt -> startAt >= baseEpochMillis && canDecorate(i) }
.distinct()
.forEach { startAt ->
val gap = TimeUnit.MILLISECONDS
.toMinutes(startAt - baseEpochMillis) * heightPerMinute
val top = first.top + gap
if (top > parent.height) return@forEach
c.drawTextAtCenter(
formatUnixMillis(startAt),
Rect(0, top.toInt(), width, (top + textHeight).toInt()),
textPaint
)
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val startAtList = (0 until adapter.itemCount).map(this::getStartUnixMillis)
val first = parent.children.minBy { it.top } ?: return
val baseEpochMillis = startAtList.getOrNull(first.layoutPosition) ?: return
startAtList
.filterIndexed { i, startAt -> startAt >= baseEpochMillis && canDecorate(i) }
.distinct()
.forEach { startAt ->
val gap = TimeUnit.MILLISECONDS
.toMinutes(startAt - baseEpochMillis) * heightPerMinute
val top = first.top + gap
if (top > parent.height) return@forEach
c.drawTextAtCenter(
formatUnixMillis(startAt),
Rect(0, top.toInt(), width, (top + textHeight).toInt()),
textPaint
)
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val startAtList = (0 until adapter.itemCount).map(this::getStartUnixMillis)
val first = parent.children.minBy { it.top } ?: return
val baseEpochMillis = startAtList.getOrNull(first.layoutPosition) ?: return
startAtList
.filterIndexed { i, startAt -> startAt >= baseEpochMillis && canDecorate(i) }
.distinct()
.forEach { startAt ->
val gap = TimeUnit.MILLISECONDS
.toMinutes(startAt - baseEpochMillis) * heightPerMinute
val top = first.top + gap
if (top > parent.height) return@forEach
c.drawTextAtCenter(
formatUnixMillis(startAt),
Rect(0, top.toInt(), width, (top + textHeight).toInt()),
textPaint
)
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val startAtList = (0 until adapter.itemCount).map(this::getStartUnixMillis)
val first = parent.children.minBy { it.top } ?: return
val baseEpochMillis = startAtList.getOrNull(first.layoutPosition) ?: return
startAtList
.filterIndexed { i, startAt -> startAt >= baseEpochMillis && canDecorate(i) }
.distinct()
.forEach { startAt ->
val gap = TimeUnit.MILLISECONDS
.toMinutes(startAt - baseEpochMillis) * heightPerMinute
val top = first.top + gap
if (top > parent.height) return@forEach
c.drawTextAtCenter(
formatUnixMillis(startAt),
Rect(0, top.toInt(), width, (top + textHeight).toInt()),
textPaint
)
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val startAtList = (0 until adapter.itemCount).map(this::getStartUnixMillis)
val first = parent.children.minBy { it.top } ?: return
val baseEpochMillis = startAtList.getOrNull(first.layoutPosition) ?: return
startAtList
.filterIndexed { i, startAt -> startAt >= baseEpochMillis && canDecorate(i) }
.distinct()
.forEach { startAt ->
val gap = TimeUnit.MILLISECONDS
.toMinutes(startAt - baseEpochMillis) * heightPerMinute
val top = first.top + gap
if (top > parent.height) return@forEach
c.drawTextAtCenter(
formatUnixMillis(startAt),
Rect(0, top.toInt(), width, (top + textHeight).toInt()),
textPaint
)
}
}
Timetable
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override fun onDrawOver(c: Canvas, parent: RecyclerView,
state: RecyclerView.State) {
…
val startAtList = (0 until adapter.itemCount).map(this::getStartUnixMillis)
val first = parent.children.minBy { it.top } ?: return
val baseEpochMillis = startAtList.getOrNull(first.layoutPosition) ?: return
startAtList
.filterIndexed { i, startAt -> startAt >= baseEpochMillis && canDecorate(i) }
.distinct()
.forEach { startAt ->
val gap = TimeUnit.MILLISECONDS
.toMinutes(startAt - baseEpochMillis) * heightPerMinute
val top = first.top + gap
if (top > parent.height) return@forEach
c.drawTextAtCenter(
formatUnixMillis(startAt),
Rect(0, top.toInt(), width, (top + textHeight).toInt()),
textPaint
)
}
}
Timetable
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‣ %JWJEFSͷඳըʹศར
‣ ͦͷؾʹͳΕଟ࠼ͳ%FDPSBUJPO͕Մೳ
‣ PO%SBX
PO%SBX0WFSεΫϩʔϧͷͨͼʹ࣮ߦ͞ΕΔͷͰॏ͍ॲཧ
͍͍ͯͳ͍Ͱ͢
‣ ಉ༷ʹɺΠϯελϯεͷੜͳΔ͘ݮΒͨ͠΄͏͕ྑ͍
Hack RecyclerView.ItemDecoration
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Thank you