IOS开发之——绘制下载进度

文章搬运来源：https://blog.csdn.net/Calvin_zhou/article/details/112002012
作者：PGzxc

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一 概述

本文介绍拖动Slider时，通过自定义View

• Label显示当前的Slider的数字大小
• Progress显示Sliderder的弧度

二 绘制进度

2.1 自定义ProgressView

设置要改变的值progress(ProgressView.h)

@interface ProgressView : UIView
@property (nonatomic,assign) CGFloat progress;
@end

Label和弧度显示

#import "ProgressView.h"
@interface ProgressView ()
@property (nonatomic,weak) UILabel *label;
@end
@implementation ProgressView

- (UILabel *)label
{
    if (_label==nil) {
        UILabel *label=[[UILabel alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
        label.textAlignment=NSTextAlignmentCenter;
        [self addSubview: label];
        _label=label;
    }
    return  _label;
}
- (void)setProgress:(CGFloat)progress
{
    _progress=progress;
    self.label.text=[NSString stringWithFormat:@"%.2f%%",progress*100];
    [self setNeedsDisplay];
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
    //1.获取上下文
    CGContextRef ctx=UIGraphicsGetCurrentContext();
    //2.拼接路径
    CGPoint center=CGPointMake(50, 50);
    CGFloat radius=50-2;
    CGFloat startA=-M_PI_2;
    CGFloat endA=-M_PI_2+_progress*M_PI*2;
    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

2.2 ViewController中设置Slider改变

#import "ViewController.h"
#import "ProgressView.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet ProgressView *progressView;
@end

@implementation ViewController
- (IBAction)valueChange:(UISlider *)sender
{
    _progressView.progress=sender.value;
    NSLog(@"%f",sender.value);
}
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}
@end

三 效果图