iOS Quartz2D模拟下载进度条

效果图：

步骤：

　　1.在StoryBoard中拖入一个控制器添加UISlider和UIView 2个控件

　　2.在控制器中连线监听UISlider的值变化事件、HJProgressView属性,把变化的值传递给自定义UIView

　　3.自定义HJProgressView重写progressValue属性set方法,重绘视图中得文字和弧度值

控制器代码：

#import "ViewController.h"
#import "HJProgressView.h"

@interface ViewController ()

@property (nonatomic,strong) IBOutlet HJProgressView *progressView;

- (IBAction)didSliderValueChange:(UISlider *)sender;

@end

@implementation ViewController

- (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.
}

/**
 *  sender.value值 0.0~1.0
 *
 *  @param sender <#sender description#>
 */
- (IBAction)didSliderValueChange:(UISlider *)sender {
    NSLog(@"%f",sender.value);
    self.progressView.progressValue = sender.value;
}

@end

自定义视图代码：

//
//  HJProgressView.m
//  画进度条
//
//  Created by HJiang on 15/1/2.
//  Copyright (c) 2015年 HJiang. All rights reserved.
//

#import "HJProgressView.h"

@interface HJProgressView()

// 定义属性保存上次的弧度起始
//@property (nonatomic,assign) CGFloat endAngle;

@end

@implementation HJProgressView

- (void)setProgressValue:(float)progressValue{
    _progressValue = progressValue;

    // 重新绘制ProgressView图形
    [self setNeedsDisplay];
}

/**
 *  绘制进度条
 *  x,y 圆心
 *  radius 半径
 *  startAngle 画弧的起始位置
 *  endAngel 画弧的结束位置
 *  clockwise 0 顺针 1 逆时针
 *  @param rect rect description
 */
- (void)drawRect:(CGRect)rect{

    // 1.设置进度文字
    CGFloat w = 40;
    CGFloat h = 30;
    CGFloat x = 13;
    CGFloat y = rect.size.height/2-5;
//    NSString *progressText = [NSString stringWithFormat:@"%.02f",self.progressValue];
    // 输出进度百分比数字
    NSMutableString *progressText = [NSMutableString string];
    [progressText appendFormat:@"%.01f",self.progressValue * 100];
    [progressText appendString:@"%"];

    // 控制文字字体大小和颜色属性
     NSDictionary *attrs = @{NSFontAttributeName:[UIFont systemFontOfSize:10],NSForegroundColorAttributeName:[UIColor redColor]};
    [progressText drawInRect:CGRectMake(x, y, w, h) withAttributes:attrs];

    CGContextRef ctx = UIGraphicsGetCurrentContext();
    // 设置颜色
    CGContextSetRGBStrokeColor(ctx, 0.5, 0.5, 0.5, 1);

    // 设置线条大小
    CGContextSetLineWidth(ctx, 3);

    // 2.绘制弧形进度
    CGFloat endAngle = self.progressValue * 2 * M_PI - M_PI_4;

    CGContextAddArc(ctx, 30, 30, 25,-M_PI_4, endAngle, 0);

    CGContextStrokePath(ctx);

}

@end