ios block dispatch_queue_t 使用demo.

最新推荐文章于 2025-07-25 09:27:59 发布

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本文介绍了一个使用Block和GCD实现的iOS图片异步加载类CWImageInfo。该类能够从网络下载图片，并在主线程中更新UI，适用于大量图片的预加载场景。

关于block的介绍我就不多说了.

dispatch_queue_t 还在学习了解当中..

2者结合的好处就是异步处理数据.在方法内部返回结果,直接可以直接使用方法类的变量,类的成员和变量等..优化减少代码量.

使用的IDE是xcode4.5测试版.

代码使用ARC模式.ios6下面dispatch_queue_release已经取消.低于ios6版本的SDK在CWImageInfo的dealloc内添加.

dispatch_queue_release(_queue);

新建 CWImageInfo类.

#import <Foundation/Foundation.h>

@interface CWImageInfo : NSObject {
    
    //block
    void (^_block_) (UIImage *image, NSUInteger nTag, NSString *sKey);
    
    dispatch_queue_t    _queue_;
}

- (BOOL) downloadWithURL:(NSURL *) url
                     tag:(NSUInteger) nTag
                     key:(NSString *) sKey;


#if NS_BLOCKS_AVAILABLE

- (void) setCompleteBlock:(void (^)(UIImage *image, NSUInteger nTag, NSString *sKey))block;

- (BOOL) downloadWithURL:(NSURL *) url
                     tag:(NSUInteger) nTag
                     key:(NSString *) sKey
                   block:(void (^)(UIImage *image, NSUInteger nTag, NSString *sKey))block;

#endif
@end

实现代码:

#import "CWImageInfo.h"

@implementation CWImageInfo

- (id) init {

    if (self = [super init]) {
        if (_queue_ == nil) {
            _queue_ = dispatch_queue_create("com.watsy.imageDownload", nil);
        }
    }
    
    return self;
}

- (BOOL) downloadWithURL:(NSURL *) url
                     tag:(NSUInteger) nTag
                     key:(NSString *) sKey {
    if (url == nil) {
        return NO;
    }
    
    dispatch_async(_queue_, ^{
        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage *image = [UIImage imageWithData:data];
        
        dispatch_async(dispatch_get_main_queue(), ^{
            _block_(image, nTag, sKey);
        });
    });
    
    return YES;
}

- (BOOL) downloadWithURL:(NSURL *) url
                     tag:(NSUInteger) nTag
                     key:(NSString *) sKey
                   block:(void (^)(UIImage *image, NSUInteger nTag, NSString *sKey))block {
    if (url == nil) {
        return NO;
    }
    
    dispatch_async(_queue_, ^{
        NSData *data = [NSData dataWithContentsOfURL:url];
        UIImage *image = [UIImage imageWithData:data];
        
        dispatch_async(dispatch_get_main_queue(), ^{
            block(image, nTag, sKey);
        });
    });
    
    return YES;
}

- (void) setCompleteBlock:(void (^) (UIImage *image, NSUInteger nTag, NSString *sKey)) block {
    _block_ = block;
}

@end

修改启动入口:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil];
    UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:self.viewController];
    self.window.rootViewController = navController;
    [self.window makeKeyAndVisible];
    return YES;
}

ViewController.m内添加

- (void) viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    
    UIActivityIndicatorView *IndicatorView = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0, 0, 25, 25)];
    IndicatorView.backgroundColor = [UIColor clearColor];
    IndicatorView.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhite;
    
    UIBarButtonItem *refreshItem = [[UIBarButtonItem alloc] initWithCustomView:IndicatorView];
    self.navigationItem.rightBarButtonItem = refreshItem;
    [IndicatorView startAnimating];
    
    NSArray *imageAddArray = [NSArray arrayWithObjects:
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175139918.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175139846.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175140661.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175140907.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175143708.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175143551.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175144636.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175144761.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175147655.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175147652.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175148276.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175148942.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175148505.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175148894.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175149393.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175149643.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175149315.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175149619.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175150388.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175150462.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175150902.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175150699.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175151668.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175151565.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175151818.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175151769.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175152107.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175152489.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175152906.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175152111.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175153957.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175153205.jpg",
                              @"http://www.xuefo.net/user/editor/uploadfile/20111128175153252.jpg",
                              @"",nil];
    NSMutableArray *imageArray = [[NSMutableArray alloc] initWithCapacity:10];
    
    CWImageInfo *cImgInfo = [[CWImageInfo alloc] init];
    for (int i = 0; i < [imageAddArray count]; i++) {
        NSURL *url = [NSURL URLWithString:[imageAddArray objectAtIndex:i]];
        
        [cImgInfo downloadWithURL:url
                              tag:i
                              key:[url path]
                            block:^(UIImage *image, NSUInteger nIndex, NSString *sKey){
                                
                                NSLog(@"download  index:%d key:%@",nIndex,sKey);
                                
                                if (image != nil) {
                                    [imageArray addObject:image];
                                }
                                     //全部下载完毕
                                 if(nIndex == [imageAddArray count] - 1) {
                                     self.navigationItem.rightBarButtonItem = nil;
                                     self.ibAnimationImageView.animationImages = imageArray;
                                     self.ibAnimationImageView.animationDuration = nIndex;
                                     [self.ibAnimationImageView startAnimating];
                                 }
                            }];
    }
}