多线程GCD用法

 1 //  后台执行：
 2  dispatch_async(dispatch_get_global_queue(0, 0), ^{
 3       // something
 4  });
 5 
 6  // 主线程执行：
 7  dispatch_async(dispatch_get_main_queue(), ^{
 8       // something
 9  });
10 
11  // 一次性执行：
12  static dispatch_once_t onceToken;
13  dispatch_once(&onceToken, ^{
14      // code to be executed once
15  });
16 
17  // 延迟2秒执行：
18  double delayInSeconds = 2.0;
19  dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
20  dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
21      // code to be executed on the main queue after delay
22  });
23 
24  // 自定义dispatch_queue_t
25  dispatch_queue_t urls_queue = dispatch_queue_create("blog.yang99.com", NULL);
26  dispatch_async(urls_queue, ^{  
27 　 　// your code 
28  });
29  dispatch_release(urls_queue); 




31  // 合并汇总结果
32  dispatch_group_t group = dispatch_group_create();
33  dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
34       // 并行执行的线程一
35  });
36  dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
37       // 并行执行的线程二
38  });
39  dispatch_group_notify(group, dispatch_get_global_queue(0,0), ^{
40       // 汇总结果
41  });

 1 - (void)initializeUserinterface{
 2     self.indictorImageView.hidden = NO;
 3     [self.indictorImageView startAnimating];
 4     dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
 5         NSURL *url = [NSURL URLWithString:@"http://www.youdao.com"];
 6         NSError *error;
 7         NSString *data = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
 8         if (data != nil) {
 9             dispatch_async(dispatch_get_main_queue(), ^{
10                 [self.indictorImageView stopAnimating];
11                 self.indictorImageView.hidden = YES;
12                 self.contentLabel.text = data;//文本显示
13                 NSLog(@"data = %@",data);
14                 [_webViewss loadHTMLString:data baseURL:url];//加载网页
15             });
16         }else{
17             NSLog(@"error when download:%@",error);
18         }
19     });
20 }

 1 // AppDelegate.h文件
 2 @property (assign, nonatomic) UIBackgroundTaskIdentifier backgroundUpdateTask;
 3 
 4 // AppDelegate.m文件
 5 - (void)applicationDidEnterBackground:(UIApplication *)application
 6 {
 7     [self beingBackgroundUpdateTask];
 8     // 在这里加上你需要长久运行的代码
 9     [self endBackgroundUpdateTask];
10 }
11 
12 - (void)beingBackgroundUpdateTask
13 {
14     self.backgroundUpdateTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
15         [self endBackgroundUpdateTask];
16     }];
17 }
18 
19 - (void)endBackgroundUpdateTask
20 {
21     [[UIApplication sharedApplication] endBackgroundTask: self.backgroundUpdateTask];
22     self.backgroundUpdateTask = UIBackgroundTaskInvalid;
23 }