用CALayer实现下载进度条

效果：

源码：

//
//  ViewController.m
//  ProgressView
//
//  Created by YouXianMing on 14/11/18.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//#import "ViewController.h"@interface ViewController ()@property (nonatomic, strong) NSTimer *timer;
@property (nonatomic, strong) CALayer *layer;@end@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];self.view.backgroundColor = [UIColor blackColor];// CALayer_layer                 = [CALayer layer];_layer.frame           = CGRectMake(50, 50, 200, 2);_layer.backgroundColor = [UIColor redColor].CGColor;[self.view.layer addSublayer:_layer];// 定时器_timer = [NSTimer scheduledTimerWithTimeInterval:1.ftarget:selfselector:@selector(timerEvent)userInfo:nilrepeats:YES];
}/***  定时器*/
- (void)timerEvent {// 显式动画_layer.frame = CGRectMake(50, 50, arc4random()%200, 2);
}@end

封装后的源码：

//
//  ProgressView.h
//  ProgressView
//
//  Created by YouXianMing on 14/11/18.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//#import <UIKit/UIKit.h>@interface ProgressView : UIView@property (nonatomic, strong) UIColor *progressColor;
@property (nonatomic, assign) CGFloat  progress;@end

//
//  ProgressView.m
//  ProgressView
//
//  Created by YouXianMing on 14/11/18.
//  Copyright (c) 2014年 YouXianMing. All rights reserved.
//#import "ProgressView.h"@interface ProgressView (){CALayer   *_backLayer;CGFloat    _frameWidth;CGFloat    _layerWidth;
}@end@implementation ProgressView- (instancetype)initWithFrame:(CGRect)frame
{self = [super initWithFrame:frame];if (self) {_backLayer       = [CALayer layer];_frameWidth      = self.bounds.size.width;_layerWidth      = 0;_backLayer.frame = CGRectMake(0, 0, _layerWidth, frame.size.height);[self.layer addSublayer:_backLayer];}return self;
}@synthesize progressColor = _progressColor;
- (void)setProgressColor:(UIColor *)progressColor {_progressColor             = progressColor;_backLayer.backgroundColor = _progressColor.CGColor;
}
- (UIColor *)progressColor {return _progressColor;
}@synthesize progress = _progress;
- (void)setProgress:(CGFloat)progress {_progress = progress;CGRect rect = _backLayer.frame;if (_progress <= 0) {rect.size.width = 0;} else if (_progress >= 1) {rect.size.width = _frameWidth;} else {rect.size.width = _progress * _frameWidth;}_backLayer.frame = rect;
}
- (CGFloat)progress {return _progress;
}@end