Kotlin--›Android 超轻,超好用,超简洁,超超超级RecyclerView分割线ItemDecoration封装
需求分析
如图所示的:
101(共2人)这一行, 顶部有 一块白色区域, 可以当做是分割线101(共2人)这一行, 底部有一个很细的分割线, 差不多撑满了一行人物信息这一行, 首次出现时, 只有底部有分割线, 而且还是 非撑满一行的效果人物信息这一行, 最后出现时, 底部没有分割线
不出意外, 很多同学的实现方式, 都是在 布局的xml中, 用padding maring backgroud 实现.
但是遇到这种相同type类型的item, 只有中间有分割线, 最后一条没有分割线的情况, 估计就有点棘手了.
莫慌, 看完本文, 你能轻松应对各种恶心的分割线.
具体实现
继承 RecyclerView.ItemDecoration , 实现 核心的 getItemOffsets onDraw onDrawOver 方法, 通常 只需要实现 getItemOffsets onDraw 即可. 如果需要悬停效果, 才需要实现 onDrawOver
为了让封装更轻量, 所以, 我并打算有任何实际操作方法.
只做核心业务的封装, 具体实现 丢给调用者.
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,/*指定目标, 则只回调目标前后的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 {
//前一个child
var beforeViewHolder: RecyclerView.ViewHolder? = null
//后一个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)
}
}
}
}
通过此方法, 到RecyclerView触发onDraw时, 枚举界面上的所有childView, 并且计算拿到 前一个 和 后一个 childView的viewHolder 对象.(如果有)
这样就可以通过 ViewHolder.getItemViewType 来区分, 各个item的类型, 也能够通过,
与前一个比较, 判断是否是同类型的第一个位置
与后一个比较, 判断是否是同类型的最后一个位置
有个你想要的各种信息, 绘制分割线的事, 就交给 canvas 吧.
完整代码
class DslItemDecoration : RecyclerView.ItemDecoration() {
val paint: Paint = Paint(Paint.ANTI_ALIAS_FLAG)
val tempDrawRect = Rect()
/**
* 将3个方法, 合一调用. 通过参数, 来区分是那一个方法.
*
* outRect 不为空时, 是 getItemOffsets 方法
* canvas 不为空时, 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,/*指定目标, 则只回调目标前后的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 {
//前一个child
var beforeViewHolder: RecyclerView.ViewHolder? = null
//后一个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)
}
}
}
}
}
调用例子
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)
}
}
}
}
结束…
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