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tai-nguyen2112/HeaderItemDecoration.kt

Forked from filipkowicz/HeaderItemDecoration.kt
Last active October 17, 2024 09:22
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Sticky header for RecyclerView, Item Decorator for sticky headers in Kotlin
Raw
HeaderItemDecoration.kt
package com.filipkowicz.headeritemdecorator
/*
solution based on - based on Sevastyan answer on StackOverflow
changes:
- take to account views offsets
- transformed to Kotlin
- now works on viewHolders
- try to cache viewHolders between draw's
- support for clipToPadding=false
Source:
https://stackoverflow.com/questions/32949971/how-can-i-make-sticky-headers-in-recyclerview-without-external-lib/44327350#44327350
*/
import android.graphics.*
import android.view.MotionEvent
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
class HeaderItemDecoration(
parent: RecyclerView,
private val shouldFadeOutHeader: Boolean = false,
private val isHeader: (itemPosition: Int) -> Boolean
) : RecyclerView.ItemDecoration() {
private var currentHeader: Pair<Int, RecyclerView.ViewHolder>? = null
init {
parent.adapter?.registerAdapterDataObserver(object : RecyclerView.AdapterDataObserver() {
override fun onChanged() {
// clear saved header as it can be outdated now
currentHeader = null
}
})
parent.doOnEachNextLayout {
// clear saved layout as it may need layout update
currentHeader = null
}
// handle click on sticky header
parent.addOnItemTouchListener(object : RecyclerView.SimpleOnItemTouchListener() {
override fun onInterceptTouchEvent(
recyclerView: RecyclerView,
motionEvent: MotionEvent
): Boolean {
return if (motionEvent.action == MotionEvent.ACTION_DOWN) {
motionEvent.y <= currentHeader?.second?.itemView?.bottom ?: 0
} else false
}
})
}
override fun onDrawOver(c: Canvas, parent: RecyclerView, state: RecyclerView.State) {
super.onDrawOver(c, parent, state)
//val topChild = parent.getChildAt(0) ?: return
val topChild = parent.findChildViewUnder(
parent.paddingLeft.toFloat(),
parent.paddingTop.toFloat() /*+ (currentHeader?.second?.itemView?.height ?: 0 )*/
) ?: return
val topChildPosition = parent.getChildAdapterPosition(topChild)
if (topChildPosition == RecyclerView.NO_POSITION) {
return
}
val headerView = getHeaderViewForItem(topChildPosition, parent) ?: return
val contactPoint = headerView.bottom + parent.paddingTop
val childInContact = getChildInContact(parent, contactPoint) ?: return
if (isHeader(parent.getChildAdapterPosition(childInContact))) {
moveHeader(c, headerView, childInContact, parent.paddingTop)
return
}
drawHeader(c, headerView, parent.paddingTop)
}
private fun getHeaderViewForItem(itemPosition: Int, parent: RecyclerView): View? {
if (parent.adapter == null) {
return null
}
val headerPosition = getHeaderPositionForItem(itemPosition)
if (headerPosition == RecyclerView.NO_POSITION) return null
val headerType = parent.adapter?.getItemViewType(headerPosition) ?: return null
// if match reuse viewHolder
if (currentHeader?.first == headerPosition && currentHeader?.second?.itemViewType == headerType) {
return currentHeader?.second?.itemView
}
val headerHolder = parent.adapter?.createViewHolder(parent, headerType)
if (headerHolder != null) {
parent.adapter?.onBindViewHolder(headerHolder, headerPosition)
fixLayoutSize(parent, headerHolder.itemView)
// save for next draw
currentHeader = headerPosition to headerHolder
}
return headerHolder?.itemView
}
private fun drawHeader(c: Canvas, header: View, paddingTop: Int) {
c.save()
c.translate(0f, paddingTop.toFloat())
header.draw(c)
c.restore()
}
private fun moveHeader(c: Canvas, currentHeader: View, nextHeader: View, paddingTop: Int) {
c.save()
if (!shouldFadeOutHeader) {
c.clipRect(0, paddingTop, c.width, paddingTop + currentHeader.height)
} else {
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
c.saveLayerAlpha(
RectF(0f, 0f, c.width.toFloat(), c.height.toFloat()),
(((nextHeader.top - paddingTop) / nextHeader.height.toFloat()) * 255).toInt()
)
} else {
c.saveLayerAlpha(
0f, 0f, c.width.toFloat(), c.height.toFloat(),
(((nextHeader.top - paddingTop) / nextHeader.height.toFloat()) * 255).toInt(),
Canvas.ALL_SAVE_FLAG
)
}
}
c.translate(0f, (nextHeader.top - currentHeader.height).toFloat() /*+ paddingTop*/)
currentHeader.draw(c)
if (shouldFadeOutHeader) {
c.restore()
}
c.restore()
}
private fun getChildInContact(parent: RecyclerView, contactPoint: Int): View? {
var childInContact: View? = null
for (i in 0 until parent.childCount) {
val child = parent.getChildAt(i)
val mBounds = Rect()
parent.getDecoratedBoundsWithMargins(child, mBounds)
if (mBounds.bottom > contactPoint) {
if (mBounds.top <= contactPoint) {
// This child overlaps the contactPoint
childInContact = child
break
}
}
}
return childInContact
}
/**
* Properly measures and layouts the top sticky header.
*
* @param parent ViewGroup: RecyclerView in this case.
*/
private fun fixLayoutSize(parent: ViewGroup, view: View) {
// Specs for parent (RecyclerView)
val widthSpec = View.MeasureSpec.makeMeasureSpec(parent.width, View.MeasureSpec.EXACTLY)
val heightSpec =
View.MeasureSpec.makeMeasureSpec(parent.height, View.MeasureSpec.UNSPECIFIED)
// Specs for children (headers)
val childWidthSpec = ViewGroup.getChildMeasureSpec(
widthSpec,
parent.paddingLeft + parent.paddingRight,
view.layoutParams.width
)
val childHeightSpec = ViewGroup.getChildMeasureSpec(
heightSpec,
parent.paddingTop + parent.paddingBottom,
view.layoutParams.height
)
view.measure(childWidthSpec, childHeightSpec)
view.layout(0, 0, view.measuredWidth, view.measuredHeight)
}
private fun getHeaderPositionForItem(itemPosition: Int): Int {
var headerPosition = RecyclerView.NO_POSITION
var currentPosition = itemPosition
do {
if (isHeader(currentPosition)) {
headerPosition = currentPosition
break
}
currentPosition -= 1
} while (currentPosition >= 0)
return headerPosition
}
}
inline fun View.doOnEachNextLayout(crossinline action: (view: View) -> Unit) {
addOnLayoutChangeListener { view, _, _, _, _, _, _, _, _ ->
action(
view
)
}
}
Raw
ListItem.kt
sealed class ListItem(
val name: String? = null
) {
class Header(name: String): ListItem(name = name)
class Item<T>(val data: T? = null): ListItem()
}
fun mapToListItems(
context: Context,
list: List<YourObject?>
): List<ListItem> {
val resultList = mutableListOf<ListItem>()
// TODO impl convert list
return resultList
}
Raw
MainActivity.kt
class MainActivity: Activity() {
...
private fun setupRecyclerView() {
yourAdapter = YourAdapter(this)
binding.recyclerView.apply {
layoutManager = LinearLayoutManager(context)
adapter = yourAdapter
addItemDecoration(
HeaderItemDecoration(this, isHeader = yourAdapter!!::isHeader)
)
}
}
...
}
Raw
YourAdapter.kt
class YourAdapter(
private var data: List<ListItem?> = listOf()
) :
RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return when(viewType) {
R.layout.item_custom ->
ItemViewHolder(parent.viewBinding(ItemCustomBinding::inflate))
else ->
HeaderViewHolder(parent.viewBinding(ItemHeaderBinding::inflate))
}
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val item = data[position]
when (holder) {
is ItemViewHolder -> {
val yourObject =
(item as ListItem.Item<*>).data as YourObject
holder.bindTo(yourObject)
}
else -> (holder as HeaderViewHolder).bind(item as ListItem.Header)
}
}
override fun getItemCount(): Int {
return data.size
}
override fun getItemViewType(position: Int): Int {
return when (data[position]) {
is ListItem.Item<*> -> R.layout.item_custom
else -> R.layout.item_header
}
}
fun updateData(listActions: List<ListItem?>) {
this.data = listActions
notifyDataSetChanged()
}
fun isHeader(position: Int) = getItemViewType(position) == R.layout.item_header
inner class ItemViewHolder(
val binding: ItemCustomBinding
) : RecyclerView.ViewHolder(binding.root) {
fun bindTo(
item: YourObject?
) {
}
}
inner class HeaderViewHolder(
val binding: ItemHeaderBinding
): RecyclerView.ViewHolder(binding.root) {
fun bind(item: ListItem.Header) {
binding.textHeader.text = item.name
binding.lineHeader.visibility = if (bindingAdapterPosition > 0) View.VISIBLE else View.INVISIBLE
}
}
}
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