IOS第16天(2,Quartz2D下载进度条）

*************自定义下载的view的方法

#import "HMProgressView.h"

@interface HMProgressView()

@property (nonatomic, weak) UILabel *label;

@end

@implementation HMProgressView

- (UILabel *)label
{
    if (_label == nil) {
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
        label.textAlignment = NSTextAlignmentCenter;

        [self addSubview:label];
        _label = label;
    }
    return _label;
}

- (void)setProgress:(CGFloat)progress
{
    _progress = progress;
    self.label.text = [NSString stringWithFormat:@"%.2f%%",progress * ];   //文字

//    [self drawRect:self.bounds];
    // 重新绘制
    // 在view上做一个重绘的标记，当下次屏幕刷新的时候，就会调用drawRect.
    [self setNeedsDisplay];
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
// 当视图显示的时候会调用 默认只会调用一次
- (void)drawRect:(CGRect)rect
{
    // Drawing code

    // 1.获取上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    // 2.拼接路径
    CGPoint center = CGPointMake(, );
    CGFloat radius =  - ;
    CGFloat startA = -M_PI_2;
    CGFloat endA = -M_PI_2 + _progress * M_PI * ;
    UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:center radius:radius startAngle:startA endAngle:endA clockwise:YES];

    // 3.把路径添加到上下文
    CGContextAddPath(ctx, path.CGPath);

    // 4.把上下文渲染到视图
    CGContextStrokePath(ctx);

}

@end

*******监听

#import "HMViewController.h"

#import "HMProgressView.h"

@interface HMViewController ()
@property (weak, nonatomic) IBOutlet HMProgressView *progressView; //自定义的view

@end

@implementation HMViewController
- (IBAction)valueChange:(UISlider *)sender {
    _progressView.progress = sender.value;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end