ios block dispatch_queue_t 使用demo.

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];
}
}];
}
}