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心血来潮动手写了个万年历，那么如果要动手封装万年历，你可能会遇到那些问题，
（1）如果去写某一个的日历
由着这个思路展开，写某一个月的日历的，要注意的又有两个地方：1. 如何显示每天对应星期几，2 月头，月尾不够天数，用上个月月初 和下个月的月初补全。
就拿第一点来说如果要想正常显示每天是周几，其实只需要，知道第一天星期几，就可以类推出每天星期几，那要怎么知道第一天星期几呢，oc 是有提供相关的函数的给我们利用，来看看代码
+ (NSUInteger)weeklyOrdinality:(NSDate *)date
{
return [[NSCalendar currentCalendar] ordinalityOfUnit:NSDayCalendarUnit inUnit:NSWeekCalendarUnit forDate:date];
}
第二点这必须要知道这个月有多少天，上个月有多少天，便可以了，知道这个月第一天星期几，则从他的前一天补上上个月的天数
float calendarY = 0;
int calendarX = 0;
//加上上个月
for (int i = 1; i < weekday; i++) {
UILabel * day = [[UILabel alloc]initWithFrame:CGRectMake(w*calendarX, 0, w, h)];
day.text = [NSString stringWithFormat:@"%lu",daysofLastMonth-(weekday-1)+i];
day.textAlignment = NSTextAlignmentCenter;
day.textColor = [UIColor hexColorWithString:@"#45A9FC"];
day.alpha = 0.5;
day.font = [UIFont systemFontOfSize:getScaleWidth(30)];
[dayOfMonthView addSubview:day];
calendarX++;
}
//这个月
for (int i = 1; i <= daysofMonth; i++) {
UILabel * day = [[UILabel alloc]initWithFrame:CGRectMake(w*calendarX, calendarY, w, h)];
day.text = [NSString stringWithFormat:@"%d",i];
day.textColor = [UIColor hexColorWithString:@"#45A9FC"];
day.textAlignment = NSTextAlignmentCenter;
day.font = [UIFont systemFontOfSize:getScaleWidth(30)];
[dayOfMonthView addSubview:day];
if (calendarX == 6) {
calendarY += h;
calendarX = 0;
}else{
calendarX++;
}
}
//补充下个月
int nextmonthDays = dayOfMonthView.subviews.count%7;
for (int i = 1; i <= 7-nextmonthDays;i++){
UILabel * day = [[UILabel alloc]initWithFrame:CGRectMake(w*calendarX, calendarY, w, h)];
day.textColor = [UIColor hexColorWithString:@"#45A9FC"];
day.alpha = 0.5;
day.text = [NSString stringWithFormat:@"%d",i];
day.textAlignment = NSTextAlignmentCenter;
day.font = [UIFont systemFontOfSize:getScaleWidth(30)];
[dayOfMonthView addSubview:day];
calendarX++;
}
(2)如果实现可以无限的左右滑动（点击上个月和下个月）
如果实现无线的滑动，如果想要一开始就把所有年份和月份加进来就显然不现实了，所以应该在点击下一个月或者上个月动态生成，下下个月，或者上上个月的日历。
我这边基本的实现，
67B0F160-D1B3-455C-A35F-481E6550BDE5.png
但是往左边滑动的时候要记得调整当前scorllview的 横向滑动坐标，因为当contentoffset.x 等于0 是不可以继续往左滑动，可以继续参考下关键代码
if (view.tag == 3) {
UIView *subView = [self.scorllView viewWithTag:1];
[subView removeFromSuperview];
UIView *subView1 = [self.scorllView viewWithTag:2];
//则删掉最左边日历，在右边加一页
subView1.tag = 1;
view.tag = 2;
NSDate *nextdate = [TDCommonTool getMonthOfDate:date isLastMonth:NO];
UIView *nextMonthView = [self setOneMonthView:nextdate];
nextMonthView.tag = 3;
nextMonthView.x = view.x+Screen_Width;
[self.scorllView addSubview:nextMonthView];
[self.dateArr addObject:nextdate];
[self.dateArr removeObjectAtIndex:0];
self.scorllView.contentSize = CGSizeMake(getAbsoluteWdith(nextMonthView), self.scorllView.height);
}else if(view.tag == 1){
UIView *subView = [self.scorllView viewWithTag:2];
UIView *subView1 = [self.scorllView viewWithTag:3];
[subView1 removeFromSuperview];
//则删掉最右边边日历，在左边加一页
subView.tag = 3;
view.tag = 2;
NSDate *lastdate = [TDCommonTool getMonthOfDate:date isLastMonth:YES];
UIView *lastMonthView = [self setOneMonthView:lastdate];
lastMonthView.tag = 1;
[self.scorllView addSubview:lastMonthView];
[self.dateArr removeObjectAtIndex:2];
[self.dateArr insertObject:lastdate atIndex:0];
view.x = Screen_Width;
lastMonthView.x = 0;
subView.x = Screen_Width*2;
[self.scorllView setContentOffset:CGPointMake(Screen_Width, 0)];
_scrollX = Screen_Width;
}
demo 地址已上传到，觉得好可以给stars
https://github.com/heysunnyboy/calendar.git
