ios多線程GCD group

標籤：

  1 #import "HMViewController.h"  2   3 @interface HMViewController ()  4 @property (weak, nonatomic) IBOutlet UIImageView *imageView1;  5 @property (weak, nonatomic) IBOutlet UIImageView *imageView2;  6 @property (weak, nonatomic) IBOutlet UIImageView *bigImageView;  7 @end  8   9 @implementation HMViewController 10  11 - (void)viewDidLoad 12 { 13     [super viewDidLoad]; 14     // Do any additional setup after loading the view, typically from a nib. 15      16     // 圖片1: http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg 17     // 圖片2: http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg 18     /** 19      1.下載圖片1和圖片2 20       21      2.將圖片1和圖片2合并成一張圖片後顯示到imageView上 22       23      思考: 24      * 下載圖片 : 子線程 25      * 等2張圖片都下載完畢後, 才回到主線程 26      */ 27 } 28  29 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 30 { 31     // 建立一個組 32     dispatch_group_t group = dispatch_group_create(); 33      34     // 開啟一個任務下載圖片1 35     __block UIImage *image1 = nil; 36     dispatch_group_async(group, global_queue, ^{ 37         image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"]; 38     }); 39      40     // 開啟一個任務下載圖片2 41     __block UIImage *image2 = nil; 42     dispatch_group_async(group, global_queue, ^{ 43         image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg"]; 44     }); 45      46     // 同時執行下載圖片1\下載圖片2操作 47      48     // 等group中的所有任務都執行完畢, 再回到主線程執行其他動作 49     dispatch_group_notify(group, main_queue, ^{ 50         self.imageView1.image = image1; 51         self.imageView2.image = image2; 52          53         // 合并 54         UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 100), NO, 0.0); 55         [image1 drawInRect:CGRectMake(0, 0, 100, 100)]; 56         [image2 drawInRect:CGRectMake(100, 0, 100, 100)]; 57         self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext(); 58         // 關閉上下文 59         UIGraphicsEndImageContext(); 60     }); 61 //    if (self.log == NO) { 62 //        NSLog(@"-------touchesBegan"); 63 //        self.log = YES; 64 //    } 65 //    static dispatch_once_t onceToken; 66 //    dispatch_once(&onceToken, ^{ 67 //        NSLog(@"-------touchesBegan"); 68 //    }); 69 } 70  71 - (void)downlaod2image 72 { 73     dispatch_async(global_queue, ^{ 74         NSLog(@"下載圖片---%@", [NSThread currentThread]); 75          76         // 下載圖片1 77         UIImage *image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"]; 78         NSLog(@"下載完圖片1---%@", [NSThread currentThread]); 79         // 下載圖片2 80         UIImage *image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"]; 81         NSLog(@"下載完圖片2---%@", [NSThread currentThread]); 82          83         dispatch_async(main_queue, ^{ 84             NSLog(@"顯示圖片---%@", [NSThread currentThread]); 85              86             self.imageView1.image = image1; 87             self.imageView2.image = image2; 88              89             // 合并 90             UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 100), NO, 0.0); 91             [image1 drawInRect:CGRectMake(0, 0, 100, 100)]; 92             [image2 drawInRect:CGRectMake(100, 0, 100, 100)]; 93             self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext(); 94             // 關閉上下文 95             UIGraphicsEndImageContext(); 96         }); 97     }); 98 } 99 100 - (UIImage *)imageWithURL:(NSString *)urlStr101 {102     NSURL *url = [NSURL URLWithString:urlStr];103     NSData *data = [NSData dataWithContentsOfURL:url]; // 這行會比較耗時104     return [UIImage imageWithData:data];105 }106 107 - (void)delay108 {109     //    NSLog(@"----touchesBegan----%@", [NSThread currentThread]);110     111     //    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{112     //        [self performSelector:@selector(run) withObject:nil afterDelay:2.0];113     //    });114     // 1.全域並發隊列115     dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);116     117     // 2.計算任務執行的時間118     dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5.0 * NSEC_PER_SEC));119     120     // 3.會在when這個時間點, 執行queue中的任務121     dispatch_after(when, queue, ^{122         NSLog(@"----run----%@", [NSThread currentThread]);123     });124 }125 126 @end

 

ios多線程GCD group