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.f                                              target:self                                            selector:@selector(timerEvent)                                            userInfo:nil                                             repeats: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 
     
      @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