前言

 　　开个新坑,以后会慢慢更新

参考 简单理解 Kotlin 中的 inline 关键字

参考 Kotlin inline, noinline and crossinline

 

内联函数实践例子

根据传入集合里的时间戳字段,查找一天中最大的时间戳item,并且收集成集合返回

public inline fun <T> Iterable<T>.findTheDailyMaxTimestamp(crossinline predicate: (T) -> Long): List<T> {
    var currentDayTime = 0L
    val timestampArray = this.toMutableList()
    timestampArray.sortByDescending { predicate(it) }
    val returnList = mutableListOf<T>()
    for (item in timestampArray) {
        //这里是关键,从实体类中去得参数里指引的目标的字段
        val time = predicate(item)
        if (currentDayTime == 0L) {
            currentDayTime = time
            returnList.add(item)
            continue
        }
        val currentCalendar = Calendar.getInstance()
        currentCalendar.timeInMillis = currentDayTime
        val crtYear = currentCalendar.get(Calendar.YEAR)
        val crtDay = currentCalendar.get(Calendar.DAY_OF_YEAR)
        val itemCalendar = Calendar.getInstance()
        itemCalendar.timeInMillis = time
        val itemYear = itemCalendar.get(Calendar.YEAR)
        val itemDay = itemCalendar.get(Calendar.DAY_OF_YEAR)
        if (crtYear == itemYear && crtDay == itemDay) {
            continue
        }
        currentDayTime = time
        returnList.add(item)
    }
    return returnList
}

使用了 扩展函数 加 内联函数, 在一些需要查找一天里需要显示日期的数据集合使用,特别适合在下面图片中情景下使用(稍微改造还能变成按月查找)

 

 

使用:

val findList: List<FamilyBean> = mList.findTheDailyMaxTimestamp { it1 -> it1.createTime }

 

 

 

End