iOS通过CAShapeLayer和UIBezierPath画环形进度条

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：

@interface ViewController (){
    CAShapeLayer *shapeLayer;
    NSTimer *timer;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //第一步，通过UIBezierPath设置圆形的矢量路径
    UIBezierPath *circle = [UIBezierPath bezierPathWithOvalInRect: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 = [CAShapeLayer layer];
    bgLayer.frame = CGRectMake(0, 0, 200, 200);//设置Frame
    bgLayer.position = self.view.center;//居中显示
    bgLayer.fillColor = [UIColor clearColor].CGColor;//填充颜色=透明色
    bgLayer.lineWidth = 2.f;//线条大小
    bgLayer.strokeColor = [UIColor grayColor].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.layer addSublayer: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 = [CAShapeLayer layer];
    shapeLayer.frame = CGRectMake(0, 0, 200, 200);
    shapeLayer.position = self.view.center;
    shapeLayer.fillColor = [UIColor clearColor].CGColor;
    shapeLayer.lineWidth = 2.f;
    shapeLayer.strokeColor = [UIColor redColor].CGColor;
    shapeLayer.strokeStart = 0;
    shapeLayer.strokeEnd = 0;
    shapeLayer.path = circle.CGPath;
    [self.view.layer addSublayer:shapeLayer];
    
    //第四步，用一个定时器进行测试，每一秒，进度加10%
    timer = [NSTimer scheduledTimerWithTimeInterval:1.f target:self selector:@selector(animate) userInfo:nil repeats: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

#import 

@interface CircleView : 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

#import "CircleView.h"

@interface CircleView()
@property(strong,nonatomic)UIBezierPath *path;
@property(strong,nonatomic)CAShapeLayer *shapeLayer;
@property(strong,nonatomic)CAShapeLayer *bgLayer;

@end

@implementation CircleView


- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        _path = [UIBezierPath bezierPathWithOvalInRect:self.bounds];
        
        _bgLayer = [CAShapeLayer layer];
        _bgLayer.frame = self.bounds;
        _bgLayer.fillColor = [UIColor clearColor].CGColor;
        _bgLayer.lineWidth = 2.f;
        _bgLayer.strokeColor = [UIColor grayColor].CGColor;
        _bgLayer.strokeStart = 0.f;
        _bgLayer.strokeEnd = 1.f;
        _bgLayer.path = _path.CGPath;
        [self.layer addSublayer:_bgLayer];
        
        _shapeLayer = [CAShapeLayer layer];
        _shapeLayer.frame = self.bounds;
        _shapeLayer.fillColor = [UIColor clearColor].CGColor;
        _shapeLayer.lineWidth = 2.f;
        _shapeLayer.lineCap = kCALineCapRound;
        _shapeLayer.strokeColor = [UIColor redColor].CGColor;
        _shapeLayer.strokeStart = 0.f;
        _shapeLayer.strokeEnd = 0.f;
        
        
        _shapeLayer.path = _path.CGPath;
        [self.layer addSublayer:_shapeLayer];
       
    }
    return self;
}

@synthesize value = _value;
-(void)setValue:(CGFloat)value{
    _value = value;
    _shapeLayer.strokeEnd = value;
}
-(CGFloat)value{
    return _value;
}

@synthesize lineColr = _lineColr;
-(void)setLineColr:(UIColor *)lineColr{
    _lineColr = lineColr;
    _shapeLayer.strokeColor = lineColr.CGColor;
}
-(UIColor*)lineColr{
    return _lineColr;
}

@synthesize lineWidth = _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

 CircleView *view = [[CircleView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
    [self.view addSubview:view];
    view.center = self.view.center;
    [view setLineWidth:6.f];
    [view setLineColr:[UIColor redColor]];

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：

CGAffineTransform transform = CGAffineTransformIdentity;
        self.transform = CGAffineTransformRotate(transform, -M_PI / 2);