ios 多线程加载图片，并实现缓存

转载自http://blog.csdn.net/deep_explore/article/details/8144613

通过使用NSOperationQueue实现多线程加载图片，并实现缓存

新建类cc

#import <Foundation/Foundation.h>
@interface CC : NSOperation{
    NSString *url;
    NSString *imageName;
    UIImage *image;
    UIImageView *delegate;
}
@property (nonatomic,retain) NSString *url;
@property (nonatomic,retain)NSString *imageName;
@property (nonatomic,retain)UIImage *image;
@property (nonatomic,retain)UIImageView *delegate;
-(void)main;
-(id) initWith:(NSString *)url imageName:(NSString *)imageName delegate:(UIImageView *)delegate;
@end


@implementation CC
@synthesize url,delegate,image,imageName;

-(id) initWith:(NSString *)url imageName:(NSString *)imageName delegate:(UIImageView *)delegate{
    if (self = [super init]) {
        self.url = [url retain];
        self.imageName = imageName;
        self.delegate = delegate;
    }
    return self;
}

-(void) main{
    //
    NSString *cachefile = [NSTemporaryDirectory() stringByAppendingPathComponent: self.imageName];
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:self.url]];
    [data writeToFile:cachefile atomically:YES];
    
    //
    self.image = [UIImage imageWithData:data];
    [self performSelectorOnMainThread:@selector(ok) withObject:nil waitUntilDone:NO];
}
-(void)ok{
    [self.delegate setImage:self.image]
}
@end

然后在viewcontroller中调用

//成员对列的初始化
  queue=[[NSOperationQueue alloc]init];
//图片资源都在数组里面了
arry=[NSArray arrayWithObjects:@"http://static2.dmcdn.net/static/video/451/838/44838154:jpeg_preview_small.jpg?20120509163826",
          @"http://static2.dmcdn.net/static/video/656/177/44771656:jpeg_preview_small.jpg?20120509154705",
          @"http://static2.dmcdn.net/static/video/629/228/44822926:jpeg_preview_small.jpg?20120509181018",
          @"http://static2.dmcdn.net/static/video/116/367/44763611:jpeg_preview_small.jpg?20120509101749",
          @"http://static2.dmcdn.net/static/video/340/086/44680043:jpeg_preview_small.jpg?20120509180118",
          @"http://static2.dmcdn.net/static/video/666/645/43546666:jpeg_preview_small.jpg?20120412153140",
          @"http://static2.dmcdn.net/static/video/771/577/44775177:jpeg_preview_small.jpg?20120509183230",
          @"http://static2.dmcdn.net/static/video/810/508/44805018:jpeg_preview_small.jpg?20120508125339",
          @"http://static2.dmcdn.net/static/video/152/008/44800251:jpeg_preview_small.jpg?20120508103336",
          @"http://static2.dmcdn.net/static/video/694/741/35147496:jpeg_preview_small.jpg?20120508111445",
          @"http://static2.dmcdn.net/static/video/988/667/44766889:jpeg_preview_small.jpg?20120508130425",
          @"http://static2.dmcdn.net/static/video/282/467/44764282:jpeg_preview_small.jpg?20120507130637",
          @"http://static2.dmcdn.net/static/video/754/657/44756457:jpeg_preview_small.jpg?20120507093012",
          @"http://static2.dmcdn.net/static/video/831/107/44701138:jpeg_preview_small.jpg?20120506133917",
          @"http://static2.dmcdn.net/static/video/411/057/44750114:jpeg_preview_small.jpg?20120507014914",
          @"http://static2.dmcdn.net/static/video/894/547/44745498:jpeg_preview_small.jpg?20120509183004",
          @"http://static2.dmcdn.net/static/video/082/947/44749280:jpeg_preview_small.jpg?20120507015022",
          @"http://static2.dmcdn.net/static/video/833/347/44743338:jpeg_preview_small.jpg?20120509183004",
          @"http://static2.dmcdn.net/static/video/683/666/44666386:jpeg_preview_small.jpg?20120505111208",nil］；

  

在tableview中实现图片的加载

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{

  NSString *identifity=[NSString  stringWithFormat:@"identify%d%d",indexPath.section,indexPath.row ];
    UITableViewCell *cell=(UITableViewCell *)[tableView dequeueReusableCellWithIdentifier:identifity];
    if (cell==nil) {
        cell=[[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:identifity];
        cell.selectionStyle=UITableViewCellSelectionStyleNone;

 NSString *filename=[NSString stringWithFormat:@"%d",indexPath.row];
        NSLog(@"filename=====%@",filename);
        NSString *cachefile=[NSTemporaryDirectory() stringByAppendingPathComponent:filename];
        
        NSLog(@"cachefile=======-----%@",cachefile);
        UIImage *Image=[UIImage imageWithContentsOfFile:cachefile];
        if (Image) {
            cell.imageView.image=Image;
            NSLog(@"有缓存，");
        }else{
             NSLog(@"无缓存，");
            NSLog(@"arry===%@",[arry objectAtIndex:indexPath.row]);
            CC *o = [[CC alloc] initWith:[[arry retain] objectAtIndex:indexPath.row] imageName:[NSString stringWithFormat:@"%d",indexPath.row] delegate:cell.imageView];
            [queue addOperation:o];
            cell.imageView.Image=[UIImage imageNamed:@"default.png"];

         ／／记得arry要retain，要不然滑动时回内存崩溃[[arry retain] objectAtIndex:indexPath.row] 这样写正确

｝

}

删除图片缓存方法

＃define K_LOCATION_IMG_COUNT 200

+ (void)checkLocationImgAndRemove {
    NSString *AppPath=[NSHomeDirectory() stringByAppendingString:@"/Documents/Images/PermanentStore/"];
    NSFileManager *manager = [NSFileManager defaultManager];
    if([manager fileExistsAtPath:AppPath]) {
        NSArray *locationImgArray = [manager contentsOfDirectoryAtPath:AppPath error:nil];
        if ([locationImgArray count] > [K_LOCATION_IMG_COUNT intValue]) {
            [manager removeItemAtPath:AppPath error:nil];
        }
    }
}
@"/Documents/Images/PermanentStore/"自定，是做缓存图片的文件夹路径！

清除webview中的缓存

http://stackoverflow.com/questions/2523435/how-to-clear-uiwebview-cache