最近因项目需求，修改原有下载进度条，特做此记录！

下载Demo

为UIImage创建分类，并动态添加ProgressValue属性,根据当前进度来选择图片

 #import <UIKit/UIKit.h>
 @interface UIImageView (Property)
 @property(nonatomic,assign)CGFloat progressValue
 @end
 #import "UIImageView+Property.h"
 #import <objc/runtime.h>

 static char progressValue;

 @implementation UIImageView (Property)

- (CGFloat)progressValue
{
    return [objc_getAssociatedObject(self, &progressValue) floatValue];
}
- (void)setProgressValue:(CGFloat)progressValue
{
    objc_setAssociatedObject(self, &progressValue, [NSString stringWithFormat:@"%f",progressValue], OBJC_ASSOCIATION_COPY);
    NSLog(@"p-%f",progressValue);
    if (progressValue == 0.0) {
        [self setImage:[UIImage imageNamed:@"download0"]];
    }else if (0.0<progressValue <=0.1) {
        [self setImage:[UIImage imageNamed:@"download1"]];
    }else if (0.1<progressValue <= 0.2){
        [self setImage:[UIImage imageNamed:@"download2"]];
    }else if (0.2<progressValue <=0.3){
        [self setImage:[UIImage imageNamed:@"download3"]];
    }else if (0.3<progressValue <=0.4){
        [self setImage:[UIImage imageNamed:@"download4"]];
    }else if (0.4<progressValue <=0.5){
        [self setImage:[UIImage imageNamed:@"download5"]];
    }else if (0.5<progressValue <=0.6){
        [self setImage:[UIImage imageNamed:@"download6"]];
    }else if (0.7<progressValue <=0.8){
        [self setImage:[UIImage imageNamed:@"download7"]];
    }else if (0.8<progressValue <=0.9){
        [self setImage:[UIImage imageNamed:@"download8"]];
    }else if (0.9<progressValue <1.0){
        [self setImage:[UIImage imageNamed:@"download9"]];
    }else{
        [self setImage:[UIImage imageNamed:@"download10"]];
   }
}

@end

----------------------------华丽分割线---------------------

 #import "ViewController.h"
 #import "UIImageView+Property.h"

 @interface ViewController ()
 {
   NSTimer *_timer;
 }
 @property(nonatomic,strong)UIImageView *progressView;
 @end

 @implementation ViewController
 - (UIImageView *)progressView
 {
    if (!_progressView) {
    _progressView = [[UIImageView alloc] init];
    _progressView.center = self.view.center;
    _progressView.bounds = CGRectMake(0,0,250,54);
    
    }
    return _progressView;
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    [self.view addSubview:self.progressView];
    NSLog(@"--------%f",self.progressView.progressValue);
    if (!_timer) {
        _timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(animation) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop]addTimer:_timer forMode:NSDefaultRunLoopMode];
    }
}
static CGFloat value = 0;
- (void)animation
{
    value += 0.1;

    if (value >= 1.0) {
        [_timer invalidate];
        _timer = nil;
        [self.progressView removeFromSuperview];
        value = 0;
        return;
    }
self.progressView.progressValue = value;

}
- (void)viewDidLoad {
    [super viewDidLoad];
   self.view.backgroundColor = [UIColor grayColor];
}

在实际项目中一般使用SDWebImageDownloader下载

[[SDWebImageDownloader sharedDownloader]downloadImageWithURL:[NSURL URLWithString:@""] options:SDWebImageDownloaderHighPriority progress:^(NSInteger receivedSize, NSInteger expectedSize) {

//在此给分类中的的progressVaule赋值 

 } completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
}];

运行效果图

下载进度条.jpg