iOS_SDWebImage框架分析

#import <SDWebImage/UIImageView+WebCache.h>

...

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *MyIdentifier = @"MyIdentifier";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];

    if (cell == nil)
    {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault
                                       reuseIdentifier:MyIdentifier] autorelease];
    }

    // Here we use the new provided sd_setImageWithURL: method to load the web image
    [cell.imageView sd_setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
                      placeholderImage:[UIImage imageNamed:@"placeholder.png"]];
　　
    cell.textLabel.text = @"My Text";
    return cell;
}

 NSURL *url = [NSURL URLWithString:@"http://127.0.0.1/userManager/0.png"];
    //SDWebImageManager管理器继承与UIImageView+WedCache。已异步的方式进行下载图片到缓冲区。
    SDWebImageManager *manager = [SDWebImageManager sharedManager];
    [manager downloadImageWithURL:url options:0 progress:^(NSInteger receivedSize, NSInteger expectedSize) {
        NSLog(@"%ld,%ld",receivedSize,expectedSize);
    }
    completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
        //为imageView设置图片为下载的图片
        [self.imageView setImage:image];
        //打印图片的来源
        NSLog(@"%@",imageURL);
    }];

[SDWebImageDownloader.sharedDownloader downloadImageWithURL:imageURL
                                                    options:0
                                                   progress:^(NSInteger receivedSize, NSInteger expectedSize)
                                                   {
                                                       // progression tracking code
                                                   }
                                                   completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished)
                                                   {
                                                       if (image && finished)
                                                       {
                                                           // do something with image
                                                       }
                                                   }];

添加自定义的只读缓存路径，其中这是可选的，如果没有指定，系统会默认
#import "SDWebImage/SDImageCache.h"
#import "AppDelegate.h"
......
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//添加自定义的只读缓存路径：可选的
    NSString *bundledPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"CustomPathImages"];
    [[SDImageCache sharedImageCache] addReadOnlyCachePath:bundledPath];
    ......    
}

#import "MasterViewController.h"
#import "SDWebImage/UIImageView+WebCache.h"
......
//清理缓存，
- (void)flushCache
{
    /**
     *  1、SDImageCache是怎么做数据管理的?
     SDImageCache分两个部分，一个是内存层面的，一个是硬盘层面的。
     内存层面的相当是个缓存器，以Key-Value的形式存储图片。
     */
    //清理内存缓存
    [SDWebImageManager.sharedManager.imageCache clearMemory];
    //清理硬盘缓存
    [SDWebImageManager.sharedManager.imageCache clearDisk];
}
//支持屏幕旋转
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
......

//为了显示大图片，替将连接中small替换成source;

    NSString *largeImageURL = [[_objects objectAtIndex:indexPath.row] stringByReplacingOccurrencesOfString:@"small" withString:@"source"];

......

#import "DetailViewController.h"
#import "SDWebImage/UIImageView+WebCache.h"
......
- (void)configureView
{
    if (self.imageURL) {
        //创建仪表器
        __block UIActivityIndicatorView *activityIndicator;
        //为防止循环引用问题，所以在block中使用imageView时要设置成弱引用，imageView中使用block，在block中如果再调用imageView时，不设置为弱引用，会出现循环引用问题。
        __weak UIImageView *weakImageView = self.imageView;
        [self.imageView sd_setImageWithURL:self.imageURL
                          placeholderImage:nil
                                   options:SDWebImageProgressiveDownload
                                  progress:^(NSInteger receivedSize, NSInteger expectedSize) {
                                      //检测是否已经存在啦！，如果没有在新创建出一个
                                      if (!activityIndicator) {
                                          //将新创建的仪表器添加到imageView视图中
                                          [weakImageView addSubview:activityIndicator = [UIActivityIndicatorView.alloc initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray]];
                                          activityIndicator.center = weakImageView.center;
                                          //开启动画，转吧！小宇宙
                                          [activityIndicator startAnimating];
                                      }
                                  }
                                 completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL){
                                     //将仪表器从imageView视图中进行删除
                                     [activityIndicator removeFromSuperview];
                                     activityIndicator = nil;
                                 }];
    }
}
......

#import "MasterViewController.h"
#import "SDWebImage/UIImageView+WebCache.h"
......
/**
     *  参数解析：
        1.获取图片的路径
        2.设置占位图片
        3.options选项：当indexPath.row为0时，执行 SDWebImageRefreshCached：刷新缓存
     */
    [cell.imageView sd_setImageWithURL:[NSURL URLWithString:[_objects objectAtIndex:indexPath.row]]
                      placeholderImage:[UIImage imageNamed:@"placeholder"] options:indexPath.row == 0 ? SDWebImageRefreshCached : 0];
......