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UIBezierPath可以绘制矢量路径，而CAShapeLayer是Layer的子类，可以在屏幕进行绘制，本文主要思想是：CAShapeLayer按照UIBezierPath的矢量路径进行绘制。
效果图如图：
方法如下：
[objc]view plaincopy
@interfaceViewController (){
CAShapeLayer*shapeLayer;
NSTimer*timer;
}
@end
@implementationViewController
- (void)viewDidLoad {
[superviewDidLoad];
//第一步，通过UIBezierPath设置圆形的矢量路径
UIBezierPath*circle = [UIBezierPathbezierPathWithOvalInRect:CGRectMake(0,0,200,200)];
//第二步，用CAShapeLayer沿着第一步的路径画一个完整的环（颜色灰色，起始点0，终结点1）
CAShapeLayer*bgLayer = [CAShapeLayerlayer];
bgLayer.frame= CGRectMake(0,0,200,200);//设置Frame
bgLayer.position=self.view.center;//居中显示
bgLayer.fillColor= [UIColorclearColor].CGColor;//填充颜色=透明色
bgLayer.lineWidth=2.f;//线条大小
bgLayer.strokeColor= [UIColorgrayColor].CGColor;//线条颜色
bgLayer.strokeStart=0.f;//路径开始位置
bgLayer.strokeEnd=1.f;//路径结束位置
bgLayer.path= circle.CGPath;//设置bgLayer的绘制路径为circle的路径
[self.view.layeraddSublayer:bgLayer];//添加到屏幕上
//第三步，用CAShapeLayer沿着第一步的路径画一个红色的环形进度条，但是起始点=终结点=0，所以开始不可见
shapeLayer = [CAShapeLayerlayer];
shapeLayer.frame= CGRectMake(0,0,200,200);
shapeLayer.position=self.view.center;
shapeLayer.fillColor= [UIColorclearColor].CGColor;
shapeLayer.lineWidth=2.f;
shapeLayer.strokeColor= [UIColorredColor].CGColor;
shapeLayer.strokeStart=0;
shapeLayer.strokeEnd=0;
shapeLayer.path= circle.CGPath;
[self.view.layeraddSublayer:shapeLayer];
//第四步，用一个定时器进行测试，每一秒，进度加10%
timer = [NSTimerscheduledTimerWithTimeInterval:1.ftarget:selfselector:@selector(animate)userInfo:nilrepeats:YES];
}
-(void)animate{
shapeLayer.strokeEnd+=0.1;
}
我们可以对以上代码封装为一个CircleView，继承自View，封装后代码如下：
CircleView.h文件
[objc]view plaincopy
#import
@interfaceCircleView : UIView
@property(assign,nonatomic)CGFloat startValue;
@property(assign,nonatomic)CGFloat lineWidth;
@property(assign,nonatomic)CGFloat value;
@property(strong,nonatomic)UIColor*lineColr;
@end
CircleView.m文件
[objc]view plaincopy
#import "CircleView.h"
@interfaceCircleView()
@property(strong,nonatomic)UIBezierPath*path;
@property(strong,nonatomic)CAShapeLayer*shapeLayer;
@property(strong,nonatomic)CAShapeLayer*bgLayer;
@end
@implementationCircleView
- (instancetype)initWithFrame:(CGRect)frame
{
self= [superinitWithFrame:frame];
if(self) {
_path = [UIBezierPathbezierPathWithOvalInRect:self.bounds];
_bgLayer = [CAShapeLayerlayer];
_bgLayer.frame=self.bounds;
_bgLayer.fillColor= [UIColorclearColor].CGColor;
_bgLayer.lineWidth=2.f;
_bgLayer.strokeColor= [UIColorgrayColor].CGColor;
_bgLayer.strokeStart=0.f;
_bgLayer.strokeEnd=1.f;
_bgLayer.path= _path.CGPath;
[self.layeraddSublayer:_bgLayer];
_shapeLayer = [CAShapeLayerlayer];
_shapeLayer.frame=self.bounds;
_shapeLayer.fillColor= [UIColorclearColor].CGColor;
_shapeLayer.lineWidth=2.f;
_shapeLayer.lineCap= kCALineCapRound;
_shapeLayer.strokeColor= [UIColorredColor].CGColor;
_shapeLayer.strokeStart=0.f;
_shapeLayer.strokeEnd=0.f;
_shapeLayer.path= _path.CGPath;
[self.layeraddSublayer:_shapeLayer];
}
returnself;
}
@synthesizevalue = _value;
-(void)setValue:(CGFloat)value{
_value = value;
_shapeLayer.strokeEnd= value;
}
-(CGFloat)value{
return_value;
}
@synthesizelineColr = _lineColr;
-(void)setLineColr:(UIColor*)lineColr{
_lineColr = lineColr;
_shapeLayer.strokeColor= lineColr.CGColor;
}
-(UIColor*)lineColr{
return_lineColr;
}
@synthesizelineWidth = _lineWidth;
-(void)setLineWidth:(CGFloat)lineWidth{
_lineWidth = lineWidth;
_shapeLayer.lineWidth= lineWidth;
_bgLayer.lineWidth= lineWidth;
}
-(CGFloat)lineWidth{
return_lineWidth;
}
@end
在需要使用的ViewContrller中使用以下代码调用即可
[objc]view plaincopy
CircleView*view = [[CircleViewalloc]initWithFrame:CGRectMake(0,0,200,200)];
[self.viewaddSubview:view];
view.center=self.view.center;
[viewsetLineWidth:6.f];
[viewsetLineColr:[UIColorredColor]];
另外默认的坐标如下图（图来自http://justsee.iteye.com/blog/1972853）
有时候我们需要开始点在顶部，即（3/2）π 处，其中一个思路是将整个View逆时针旋转90度即可，在CircleView.m的initWithFrame中添加以下代码即可：
[objc]view plaincopy
CGAffineTransform transform = CGAffineTransformIdentity;
self.transform= CGAffineTransformRotate(transform, -M_PI /2);