ios block dispatch_queue_t 使用demo.

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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];                                 }                            }];    }}