需求分析
如圖所示的:
101(共2人)這一行, 頂部有 一塊白色區域, 可以當做是分割線101(共2人)這一行, 底部有一個很細的分割線, 差不多撐滿了一行人物信息這一行, 首次出現時, 只有底部有分割線, 而且還是 非撐滿一行的效果人物信息這一行, 最後出現時, 底部沒有分割線
不出意外, 很多同學的實現方式, 都是在 佈局的xml中, 用padding maring backgroud 實現.
但是遇到這種相同type類型的item, 只有中間有分割線, 最後一條沒有分割線的情況, 估計就有點棘手了.
莫慌, 看完本文, 你能輕鬆應對各種噁心的分割線.
具體實現
繼承 RecyclerView.ItemDecoration , 實現 核心的 getItemOffsets onDraw onDrawOver 方法, 通常 只需要實現 getItemOffsets onDraw 即可. 如果需要懸停效果, 才需要實現 onDrawOver
爲了讓封裝更輕量, 所以, 我並打算有任何實際操作方法.
只做核心業務的封裝, 具體實現 丟給調用者.
override fun onDraw(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
eachChildViewHolder(parent) { beforeViewHolder, viewHolder, afterViewHolder ->
eachItemDoIt.invoke(canvas, parent, state, null, beforeViewHolder, viewHolder, afterViewHolder, false)
}
}
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
eachChildViewHolder(parent, view) { beforeViewHolder, viewHolder, afterViewHolder ->
eachItemDoIt.invoke(null, parent, state, outRect, beforeViewHolder, viewHolder, afterViewHolder, false)
}
}
核心方法
fun eachChildViewHolder(
parent: RecyclerView,
targetView: View? = null,/*指定目標, 則只回調目標前後的ViewHolder*/
callback: (
beforeViewHolder: RecyclerView.ViewHolder?,
viewHolder: RecyclerView.ViewHolder,
afterViewHolder: RecyclerView.ViewHolder?
) -> Unit
) {
val childCount = parent.childCount
for (i in 0 until childCount) {
val child = parent.getChildAt(i)
val childViewHolder = parent.findContainingViewHolder(child)
childViewHolder?.let {
//前一個child
var beforeViewHolder: RecyclerView.ViewHolder? = null
//後一個child
var afterViewHolder: RecyclerView.ViewHolder? = null
if (i >= 1) {
beforeViewHolder = parent.findContainingViewHolder(parent.getChildAt(i - 1))
}
if (i < childCount - 1) {
afterViewHolder = parent.findContainingViewHolder(parent.getChildAt(i + 1))
}
if (targetView != null) {
if (targetView == child) {
callback.invoke(beforeViewHolder, it as RBaseViewHolder, afterViewHolder)
return
}
} else {
callback.invoke(beforeViewHolder, it as RBaseViewHolder, afterViewHolder)
}
}
}
}
通過此方法, 到RecyclerView觸發onDraw時, 枚舉界面上的所有childView, 並且計算拿到 前一個 和 後一個 childView的viewHolder 對象.(如果有)
這樣就可以通過 ViewHolder.getItemViewType 來區分, 各個item的類型, 也能夠通過,
與前一個比較, 判斷是否是同類型的第一個位置
與後一個比較, 判斷是否是同類型的最後一個位置
有個你想要的各種信息, 繪製分割線的事, 就交給 canvas 吧.
完整代碼
class DslItemDecoration : RecyclerView.ItemDecoration() {
val paint: Paint = Paint(Paint.ANTI_ALIAS_FLAG)
val tempDrawRect = Rect()
/**
* 將3個方法, 合一調用. 通過參數, 來區分是那一個方法.
*
* outRect 不爲空時, 是 getItemOffsets 方法
* canvas 不爲空時, 是 onDrawOver onDraw
* isOverDraw 控制是否是 onDrawOver
* */
var eachItemDoIt: (
canvas: Canvas?, parent: RecyclerView, state: RecyclerView.State, outRect: Rect?,
beforeViewHolder: RecyclerView.ViewHolder?,
viewHolder: RecyclerView.ViewHolder,
afterViewHolder: RecyclerView.ViewHolder?,
isOverDraw: Boolean
) -> Unit =
{ _, _, _, _, _, _, _, _ -> }
override fun onDrawOver(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
eachChildRViewHolder(parent) { beforeViewHolder, viewHolder, afterViewHolder ->
eachItemDoIt.invoke(canvas, parent, state, null, beforeViewHolder, viewHolder, afterViewHolder, true)
}
}
override fun onDraw(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
eachChildRViewHolder(parent) { beforeViewHolder, viewHolder, afterViewHolder ->
eachItemDoIt.invoke(canvas, parent, state, null, beforeViewHolder, viewHolder, afterViewHolder, false)
}
}
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
eachChildRViewHolder(parent, view) { beforeViewHolder, viewHolder, afterViewHolder ->
eachItemDoIt.invoke(null, parent, state, outRect, beforeViewHolder, viewHolder, afterViewHolder, false)
}
}
fun eachChildViewHolder(
parent: RecyclerView,
targetView: View? = null,/*指定目標, 則只回調目標前後的ViewHolder*/
callback: (
beforeViewHolder: RecyclerView.ViewHolder?,
viewHolder: RecyclerView.ViewHolder,
afterViewHolder: RecyclerView.ViewHolder?
) -> Unit
) {
val childCount = parent.childCount
for (i in 0 until childCount) {
val child = parent.getChildAt(i)
val childViewHolder = parent.findContainingViewHolder(child)
childViewHolder?.let {
//前一個child
var beforeViewHolder: RecyclerView.ViewHolder? = null
//後一個child
var afterViewHolder: RecyclerView.ViewHolder? = null
if (i >= 1) {
beforeViewHolder = parent.findContainingViewHolder(parent.getChildAt(i - 1))
}
if (i < childCount - 1) {
afterViewHolder = parent.findContainingViewHolder(parent.getChildAt(i + 1))
}
if (targetView != null) {
if (targetView == child) {
callback.invoke(beforeViewHolder, it as RBaseViewHolder, afterViewHolder)
return
}
} else {
callback.invoke(beforeViewHolder, it as RBaseViewHolder, afterViewHolder)
}
}
}
}
}
調用例子
public fun RecyclerView.dslItemDecoration(init: DslItemDecoration.() -> Unit) {
addItemDecoration(DslItemDecoration().apply {
init()
})
}
dslItemDecoration {
val line = getDimen(R.dimen.wt_line)
eachItemDoIt = { canvas, _, _, outRect, _, viewHolder, afterViewHolder, _ ->
if (viewHolder.itemViewType == R.layout.item_info_group_head) {
outRect?.set(0, 10 * dpi, 0, line)
tempDrawRect.set(
0,
viewHolder.itemView.top - 10 * dpi,
viewHolder.itemView.right,
viewHolder.itemView.top
)
paint.color = getColor(R.color.wt_dark_bg)
canvas?.drawRect(tempDrawRect, paint)
tempDrawRect.set(
0,
viewHolder.itemView.top - line,
viewHolder.itemView.right,
viewHolder.itemView.top
)
paint.color = getColor(R.color.wt_line)
canvas?.drawRect(tempDrawRect, paint)
tempDrawRect.set(
0,
viewHolder.itemView.bottom,
viewHolder.itemView.right,
viewHolder.itemView.bottom - line
)
canvas?.drawRect(tempDrawRect, paint)
} else if (viewHolder.itemViewType == R.layout.item_info_single_text) {
if (afterViewHolder?.itemViewType == R.layout.item_info_single_text) {
outRect?.set(0, 0, 0, line)
paint.color = getColor(R.color.wt_line)
tempDrawRect.set(
25 * dpi,
viewHolder.itemView.bottom,
viewHolder.itemView.right,
viewHolder.itemView.bottom - line
)
canvas?.drawRect(tempDrawRect, paint)
}
}
}
}
結束…
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