关于UIPageControl 自定义样式定制的正确姿势

近来，项目中需要定制UIPageControl样式，目前知道的方式大概如下，这里简单概括：

一、修改颜色，最简单的方式：

_pageControl.pageIndicatorTintColor = [UIColor redColor];// 设置非选中页的圆点颜色
_pageControl.currentPageIndicatorTintColor = [UIColor blueColor]; // 设置选中页的圆点颜色

二、修改静态图标样式，可以采用KVO方式，这种弊端是只能静态显示，无法动态替换，且私有，危险：

[_pageControl setValue:[UIImage imageNamed:@"image1"] forKeyPath:@"_pageImage"];

[_pageControl setValue:[UIImage imageNamed:@"image2"] forKeyPath:@"_currentPageImage"];

三、替换系统默认图标，自定义样式：

常规方式便是创建一个类，继承于UIPageControl，重新set方式，这里写下核心代码，也是目前网络上的方式：

-(void) updateDots {            
     for (int i = 0; i < [self.subviews count]; i++)  {
       UIImageView *dot = [self.subviews objectAtIndex:i];
        if (i == self.currentPage) dot.image = activeImage;
       else dot.image = inactiveImage;
    }
 }

结果是程序崩溃，归咎原因：

这种方式及其危险的，因为[self.subviews objectAtIndex:i] class 为UIView, 而 UIImageView *dot = [self.subviews objectAtIndex:i]; 这句是将一个UIView转换为UIImageView, 故容易crash 掉，特此放弃如上国内方式；

四、完善上面第三种方式，转为安全的替换方式，核心代码如下：

for (UIView *subview in view.subviews) {
            if ([subview isKindOfClass:[UIImageView class]]) {
                dot = (UIImageView *)subview;
                break;
            }
        }
        

采用如上安全方式，可有效防止崩溃，至此完成项目需求，效果如下：

五、这里把整个代码放出来，帮助大家少走弯路，具体代码如下：

1、.h文件

#import 

@interface CustomPageControl : UIPageControl
@property (nonatomic, strong) UIImage *currentImage;
@property (nonatomic, strong) UIImage *inactiveImage;

@property (nonatomic, assign) CGSize currentImageSize;
@property (nonatomic, assign) CGSize inactiveImageSize;
@end

2、.m文件

#import "CustomPageControl.h"

@implementation CustomPageControl

- (instancetype)init{
    self = [super init];
    if (self) {
        self.userInteractionEnabled = NO;
    }
    return self;
}

- (void)setCurrentPage:(NSInteger)currentPage{
    [super setCurrentPage:currentPage];
 
    [self updateDots];
}


- (void)updateDots{
    for (int i = 0; i < [self.subviews count]; i++) {
        UIImageView *dot = [self imageViewForSubview:[self.subviews objectAtIndex:i] currPage:i];
        if (i == self.currentPage){
            dot.image = self.currentImage;
            dot.size = self.currentImageSize;
        }else{
            dot.image = self.inactiveImage;
            dot.size = self.inactiveImageSize;
        }
    }
}


- (UIImageView *)imageViewForSubview:(UIView *)view currPage:(int)currPage{
    UIImageView *dot = nil;
    if ([view isKindOfClass:[UIView class]]) {
        for (UIView *subview in view.subviews) {
            if ([subview isKindOfClass:[UIImageView class]]) {
                dot = (UIImageView *)subview;
                break;
            }
        }
        
        if (dot == nil) {
            dot = [[UIImageView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, view.frame.size.width, view.frame.size.height)];
           
            [view addSubview:dot];
        }
    }else {
        dot = (UIImageView *)view;
    }
    
    return dot;
}



@end

3、使用方式：

CustomPageControl *pageCtrl = [[CustomPageControl alloc] initWithFrame:CGRectMake(0, 10, mScreenWidth, 5)]; 
pageCtrl.numberOfPages = cardSwitchViewAry.count;
pageCtrl.currentPage = 0; 
pageCtrl.userInteractionEnabled = NO;
pageCtrl.inactiveImage = [UIImage imageNamed:@"ex_page_1"];
pageCtrl.inactiveImageSize = CGSizeMake(5, 5);
pageCtrl.currentImage = [UIImage imageNamed:@"ex_page_2"];
pageCtrl.currentImageSize = CGSizeMake(10, 5);


    //去掉系统自带样式
pageCtrl.currentPageIndicatorTintColor = [UIColor clearColor];
pageCtrl.pageIndicatorTintColor = [UIColor clearColor];    

至此，定制UIPageControl的正确姿势已了解，希望对大家有用。