Web image（網路影象）

該庫提供了一個支援來自Web的遠端影象的UIImageView類別

它提供了:

• 新增網路影象和快取管理到Cocoa Touch framework的UIImageView類別
• 非同步影象下載
• An asynchronous memory + disk image caching with automatic cache expiration handling
• 支援GIF動畫
• 支援WebP格式
• 後臺影象解壓
• 保證相同的url不會下載多次
• 保證偽造的URL不會嘗試一遍又一遍的下載
• 保證主執行緒永遠不會被阻塞
• Performances!
• 使用GCD和ARC

注意：SDWebImage 3.0不向後相容2.0並且最低需要iOS 5.0 的版本。如果你的iOS版本低於5.0，請使用

如何使用

Using UIImageView+WebCache category with UITableView

#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 setImageWithURL: method to load the web image
    [cell.imageView setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
                   placeholderImage:[UIImage imageNamed:@"placeholder.png"]];

    cell.textLabel.text = @"My Text";
    return cell;
}

// Here we use the new provided setImageWithURL: method to load the web image
[cell.imageView setImageWithURL:[NSURL URLWithString:@"http://www.domain.com/path/to/image.jpg"]
               placeholderImage:[UIImage imageNamed:@"placeholder.png"]
                      completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) {... completion code here ...}];

Using SDWebImageManager

SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadWithURL:imageURL
                 options:0
                 progress:^(NSUInteger receivedSize, long long expectedSize)
                 {
                     // progression tracking code
                 }
                 completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType)
                 {
                     if (image)
                     {
                         // do something with image
                     }
                 }];

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

SDImageCache *imageCache = [SDImageCache.alloc initWithNamespace:@"myNamespace"];
[imageCache queryDiskCacheForKey:myCacheKey done:^(UIImage *image)
{
    // image is not nil if image was found
}];

[[SDImageCache sharedImageCache] storeImage:myImage forKey:myCacheKey];

Using cache key filter

        下面的示例在應用程式的委託中設定一個過濾器，在使用它的快取鍵之前將從URL中刪除任何查詢字串（The following example sets a filter in the application delegate that will remove any query-string from the URL before to use it as a cache key）：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    SDWebImageManager.sharedManager.cacheKeyFilter:^(NSURL *url)
    {
        url = [[[NSURL alloc] initWithScheme:url.scheme host:url.host path:url.path] autorelease];
        return [url absoluteString];
    };

    // Your app init code...
    return YES;
}

Using dynamic image size with UITableViewCell

Handle image refresh（控制影象重新整理）

        如果你不控制你的影象伺服器，當它的內容更新時你不能改變它的url。Facebook頭像就是這種情況的例子。在這種情況下，你可以使用SDWebImageRefreshCached的標誌。這將稍微降低效能，但將會考慮到HTTP快取控制頭：

[imageView setImageWithURL:[NSURL URLWithString:@"https://graph.facebook.com/olivier.poitrey/picture"]
          placeholderImage:[UIImage imageNamed:@"avatar-placeholder.png"]
                   options:SDWebImageRefreshCached];

Add a progress indicator（新增進度指示）

Installation（安裝）

Add the SDWebImage project to your project

• Download and unzip the last version of the framework from the download page
• Right-click on the project navigator and select "Add Files to "Your Project":
• In the dialog, select SDWebImage.framework:
• Check the "Copy items into destination group's folder (if needed)" checkbox

Add dependencies（新增依賴性）

• In you application project app’s target settings, find the "Build Phases" section and open the "Link Binary With Libraries" block:
• Click the "+" button again and select the "ImageIO.framework"(還缺一個“MapKit.framework”，readme中沒提到), this is needed by the progressive download feature:

Add Linker Flag（新增連結標誌）

     Open the "Build Settings" tab, in the "Linking" section, locate the "Other Linker Flags" setting and add the "-ObjC" flag:

Import headers in your source files（匯入標頭檔案到你的資原始檔中）

#import <SDWebImage/UIImageView+WebCache.h>

Build Project（編譯工程）

Future Enhancements（未來增強功能）

Future Enhancements