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模仿SDWebImage实现异步加载图片

2024-07-13 13:37:43   239人阅读

模仿SDWebImage实现异步加载图片

SDWebImage想必大家都不陌生吧,要实现它的图片异步加载功能这个还是很简单的.

注意:此处我只实现了异步加载图片,并没有将文件缓存到本地的打算哦:)

源码:

UIImageView+YXImageView.h

////  UIImageView+YXImageView.h//  PicDemo////  Copyright (c) 2014年 Y.X. All rights reserved.//#import <UIKit/UIKit.h>@interface UIImageView (YXImageView)- (void)setImageWithURL:(NSString *)url placeholderImage:(UIImage *)placeholder;@end

UIImageView+YXImageView.m

////  UIImageView+YXImageView.m//  PicDemo////  Copyright (c) 2014年 Y.X. All rights reserved.//#import "UIImageView+YXImageView.h"@implementation UIImageView (YXImageView)- (void)setImageWithURL:(NSString *)url placeholderImage:(UIImage *)placeholder{    // 先设置placeholder    self.image = placeholder;        // 异步下载完了之后再加载新的图片    if (url)    {        // 子线程下载        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{                        NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];            NSData *data          =http://www.mamicode.com/ [NSURLConnection sendSynchronousRequest:request                                                          returningResponse:nil                                                                      error:nil];            // 主线程更新            dispatch_async(dispatch_get_main_queue(), ^{                if (data)                {                    self.image = [UIImage imageWithData:data];                    [self setNeedsDisplay];                }            });        });    }}@end

使用的源码:

RootViewController.m

////  RootViewController.m//  PicDemo////  Copyright (c) 2014年 Y.X. All rights reserved.//#import "RootViewController.h"#import "UIImageView+YXImageView.h"@interface RootViewController ()@end@implementation RootViewController- (void)viewDidLoad{    [super viewDidLoad];    UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.view.bounds];    [self.view addSubview:imageView];        [imageView setImageWithURL:@"http://pic.cnitblog.com/avatar/572952/20140226185251.png"              placeholderImage:[UIImage imageNamed:@"1.png"]];}@end

核心代码:

GCD部分就不讲解了,关键的一步是需要重绘view本身,这个涨知识了:)

除了下载图片,你还可以做其他操作呢:)


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