设计思路：给UIView增加一个分类 所有的视图都可以根据需要来进行红点显示
#import <UIKit/UIKit.h> @interface UIView (CHRRedDot) @property (readonly, nonatomic) CALayer * chr_redDotLayer; /**
红点圆心的位置，与各个边之间的距离。如果距离<=0，则忽略距离
*/
@property (nonatomic, assign) UIEdgeInsets chr_redDotEdgeInsets; /**
红点的半径，默认为4
*/
@property (nonatomic, assign) CGFloat chr_redDotRadius; /**
红点的颜色，默认为0xFF5A5A
*/
@property (nonatomic, strong) UIColor * chr_redDotColor; /**
红点是否显示
*/
@property (nonatomic, assign) BOOL chr_redDotShow; @end
#pragma mark - method
- (void)chr_updateRedDot {
CALayer *redDot = self.chr_redDotLayer;
if (self.chr_redDotShow) {
if (redDot == nil) {
redDot = [CALayer layer];
self.chr_redDotLayer = redDot;
[self.layer addSublayer:redDot];
}
redDot.backgroundColor = self.chr_redDotColor.CGColor;
[self chr_layoutRedDot];
} else {
[redDot removeFromSuperlayer];
self.chr_redDotLayer = nil;
}
} - (void)chr_layoutRedDot {
CALayer *redDot = self.chr_redDotLayer;
if (redDot == nil) return;
CGFloat radius = self.chr_redDotRadius;
redDot.cornerRadius = radius;
UIEdgeInsets edgeInsets = self.chr_redDotEdgeInsets;
CGFloat originX = edgeInsets.right <= ? edgeInsets.left - radius : self.bounds.size.width - edgeInsets.right + radius;
CGFloat originY = edgeInsets.bottom <= ? edgeInsets.top - radius : self.bounds.size.height - edgeInsets.bottom + radius;
CGFloat length = radius * ;
redDot.frame = CGRectMake(originX, originY, length, length);
}