negative or zero item sizes are not supported in the flow layout

[429329513wanting]

xcode:11.5
swift:5

    self.calendarView = CalendarView()
    self.calendarView?.frame = CGRect(x: 0, y: HT_StatusBarAndNavigationBarHeight, width: KScreenWidth, height: 200)
    calendarView?.dataSource = self
    calendarView?.delegate =  self
    calendarView?.marksWeekends = true
    calendarView?.direction = .horizontal
    calendarView?.setDisplayDate(Date())
    view.addSubview(self.calendarView!)

[429329513wanting]

//MARK: - calendarDelegate
func startDate() -> Date {

    var dateComponents = DateComponents()
    dateComponents.month = -1
    
    let today = Date()
    
    let threeMonthsAgo = self.calendarView?.calendar.date(byAdding: dateComponents, to: today)!
    
    return threeMonthsAgo!
}
func endDate() -> Date {

  var dateComponents = DateComponents()

  dateComponents.month = 12
  let today = Date()
  
  let twoYearsFromNow = self.calendarView?.calendar.date(byAdding: dateComponents, to: today)!
  
    return twoYearsFromNow!
}

func calendar(_ calendar: CalendarView, didScrollToMonth date: Date) {
    
}

func calendar(_ calendar: CalendarView, didDeselectDate date: Date) {
    
}


func headerString(_ date: Date) -> String? {
    
    return "标题"
}

func calendar(_ calendar: CalendarView, didSelectDate date: Date, withEvents events: [CalendarEvent]) {
    
}

func calendar(_ calendar: CalendarView, canSelectDate date: Date) -> Bool {
    
    return false
}

func calendar(_ calendar: CalendarView, didLongPressDate date: Date, withEvents events: [CalendarEvent]?) {
    
}