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:)网址:yii666.com
源码:
UIImageView+YXImageView.h文章来源地址:https://www.yii666.com/article/764399.html
//
// 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, ), ^{ NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
NSData *data = [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:)文章地址https://www.yii666.com/article/764399.html
