自定義圓形進度條，繪製進度條

//
// HMProgressView.m
// 02-下載進度條
//
// Created by apple on 14-9-2.
// Copyright (c) 2014年 itcast. All rights reserved.
//

＃import “HMProgressView.h”

@interface HMProgressView()

@property (nonatomic, weak) UILabel *label;

@end

@implementation HMProgressView

• (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 drawRect:self.bounds];
// 重新繪製
// 在view上做一個重繪的標記，當下次屏幕刷新的時候，就會調用drawRect.
[self setNeedsDisplay];
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
// 當視圖顯示的時候會調用 默認只會調用一次
- (void)drawRect:(CGRect)rect
{
// Drawing code

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

// 2.拼接路徑
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.把路徑添加到上下文
CGContextAddPath(ctx, path.CGPath);

// 4.把上下文渲染到視圖
CGContextStrokePath(ctx);

}

@end