Quartz2D绘制圆形进度条

#import "ViewController.h"
#import "IProgressView.h"

@interface ViewController ()

@property (strong, nonatomic) IBOutlet IProgressView *pinkView;
@property (strong, nonatomic) IBOutlet UILabel *progressLabel;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
}

- (IBAction)sliderValueChanged:(UISlider *)sender {
    float value = sender.value;
    self.progressLabel.text = [NSString stringWithFormat:@"%.1f%%", value * 100];
    self.pinkView.progress = value;
}

@end

#import <UIKit/UIKit.h>

@interface IProgressView : UIView

@property (nonatomic, assign) float progress;

@end

#import "IProgressView.h"

@implementation IProgressView

- (void)setProgress:(float)progress
{
    _progress = progress;
    [self setNeedsDisplay]; // 重绘(系统会自动调用drawRect方法)
}

- (void)drawRect:(CGRect)rect {
    // Drawing code
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGPoint center = CGPointMake(rect.size.width * 0.5, rect.size.height * 0.5);
    CGFloat radius = rect.size.width * 0.5 - 10;
    CGFloat startAngle = -M_PI_2; // 从-90°开始
    CGFloat endAngle = startAngle + self.progress * M_PI * 2;
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:center radius:radius startAngle:startAngle endAngle:endAngle clockwise:YES];
    CGContextSetLineWidth(context, 3);
    [[UIColor blueColor] setStroke];
    
    CGContextAddPath(context, path.CGPath);
    CGContextStrokePath(context);
}

@end

效果图如下：