iOS UIImageView 圆形

众所周知， UIImageView 在drawrect方法中是不走的，也就是继承UIImageView的子控件，无法在drawrect方法中重新绘制，因为该方法是失效的。

- (void)drawRect:(CGRect)rect {

    // Drawing code

    CGFloatwidth =CGRectGetWidth(rect);

    CGFloatheight =CGRectGetHeight(rect);

    CGFloatradius = width>height?height/2.0:width/2.0;

    CGMutablePathRef path = CGPathCreateMutable();

    CGPathAddArc(path,NULL, width/2.0, height/2.0, radius,0,2*M_PI,YES);

    CAShapeLayer *maskLayer = [CAShapeLayer layer];

    maskLayer.frame= rect;

    maskLayer.path= path;

    self.layer.mask= maskLayer;

}

那么怎样才能让UIImageview绘制出圆形呢？需要让他走绘制的方法，如果不能走drawrect，那么采用他还会走什么方法呢？答案是layoutSubviews, 把方法写在layoutSubviews里面即可。

#import "HZRoundImageView.h"

@implementationHZRoundImageView

- (instancetype)initWithFrame:(CGRect)frame {

    if(self= [superinitWithFrame:frame]) {

    }

    return self;

}

- (void)layoutSubviews {

    CGRectrect =self.bounds;

    // Drawing code

    CGFloatwidth =CGRectGetWidth(rect);

    CGFloatheight =CGRectGetHeight(rect);

    CGFloatradius = width>height?height/2.0:width/2.0;

    CGMutablePathRef path = CGPathCreateMutable();

    CGPathAddArc(path,NULL, width/2.0, height/2.0, radius,0,2*M_PI,YES);

    CAShapeLayer *maskLayer = [CAShapeLayer layer];

    maskLayer.frame= rect;

    maskLayer.path= path;

    self.layer.mask= maskLayer;

}

然后在其他地方调用, 无论是使用initWithFrame方法还是autolayout都可以变成圆形。

调用一个例子如下:

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    [self initUI];

}

- (void)initUI {

    HZRoundImageView *imageView = [[HZRoundImageView alloc]initWithFrame:CGRectMake(100,100,100,150)];

    [self.view addSubview:imageView];

    [imageView setBackgroundColor:[UIColor greenColor]];

    [imageView setImage:[UIImageimageNamed:@"bbs_item0"]];

    imageView.layer.masksToBounds=YES;

    [imageView mas_makeConstraints:^(MASConstraintMaker*make) {

        make.center.equalTo(self.view);

        make.width.equalTo(self.view).multipliedBy(0.8);

        make.height.equalTo(self.view).multipliedBy(0.8);

    }];

}

效果如上图。