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) 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) Y.X. All rights reserved.//#import "UIImageView+YXImageView.h"@implementation UIImageView (YXImageView)- (void)setImageWithURL:(NSString *)url placeholderImage:(UIImage *)placeholder{// 先设置placeholderself.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= [NSURLConnection sendSynchronousRequest:requestreturningResponse:nilerror: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) 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:@"/avatar/572952/0226185251.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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