iOS multithreaded GCD Group

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 @end8 9 @implementation HmviewcontrollerTen  One- (void) Viewdidload A { - [Super Viewdidload]; -     //additional setup after loading the view, typically from a nib. the      -     //Picture 1:http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg -     //Picture 2:http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg -     /** + 1. Download picture 1 and picture 2 -       + 2. Merge picture 1 and picture 2 into one picture and display to ImageView A       at thinking: - * Download Image: Sub-thread - * Wait for 2 images to be downloaded before returning to the main thread -      */ - } -  in- (void) Touchesbegan: (Nsset *) touches withevent: (Uievent *)Event - { to     //Creating a group +dispatch_group_t Group =dispatch_group_create (); -      the     //open a task download image 1 *__block UIImage *image1 =Nil; $Dispatch_group_async (Group, global_queue, ^{Panax NotoginsengImage1 = [Self Imagewithurl:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"]; -     }); the      +     //open a task download Image 2 A__block UIImage *image2 =Nil; theDispatch_group_async (Group, global_queue, ^{ +Image2 = [Self Imagewithurl:@"http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg"]; -     }); $      $     //simultaneous download image 1\ download Image 2 Operation -      -     //All tasks in the group are completed, and then go back to the main thread to perform other operations theDispatch_group_notify (Group, main_queue, ^{ -Self.imageView1.image =Image1;WuyiSelf.imageView2.image =Image2; the          -         //Merging WuUigraphicsbeginimagecontextwithoptions (Cgsizemake ( $, -), NO,0.0); -[Image1 Drawinrect:cgrectmake (0,0, -, -)]; About[Image2 Drawinrect:cgrectmake ( -,0, -, -)]; $Self.bigImageView.image =Uigraphicsgetimagefromcurrentimagecontext (); -         //Close Context - Uigraphicsendimagecontext (); -     }); A //if (Self.log = = NO) { + //NSLog (@ "-------Touchesbegan"); the //self.log = YES; - //    } $ //static dispatch_once_t Oncetoken; the //dispatch_once (&oncetoken, ^{ the //NSLog (@ "-------Touchesbegan"); the //    }); the } -  in- (void) Downlaod2image the { theDispatch_async (Global_queue, ^{ AboutNSLog (@"Download Image---%@", [Nsthread CurrentThread]); the          the         //Download Image 1 theUIImage *image1 = [Self Imagewithurl:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"]; +NSLog (@"Download Picture 1---%@", [Nsthread CurrentThread]); -         //Download Image 2 theUIImage *image2 = [Self Imagewithurl:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];BayiNSLog (@"Download Picture 2---%@", [Nsthread CurrentThread]); the          theDispatch_async (Main_queue, ^{ -NSLog (@"Show Pictures---%@", [Nsthread CurrentThread]); -              theSelf.imageView1.image =Image1; theSelf.imageView2.image =Image2; the              the             //Merging -Uigraphicsbeginimagecontextwithoptions (Cgsizemake ( $, -), NO,0.0); the[Image1 Drawinrect:cgrectmake (0,0, -, -)]; the[Image2 Drawinrect:cgrectmake ( -,0, -, -)]; theSelf.bigImageView.image =Uigraphicsgetimagefromcurrentimagecontext ();94             //Close Context the Uigraphicsendimagecontext (); the         }); the     });98 } About  --(UIImage *) Imagewithurl: (NSString *) Urlstr101 {102Nsurl *url =[Nsurl Urlwithstring:urlstr];103NSData *data = [NSData Datawithcontentsofurl:url];//This guild is time consuming .104     return[UIImage Imagewithdata:data]; the }106 107- (void) Delay108 {109     //NSLog (@ "----Touchesbegan----%@", [Nsthread CurrentThread]); the     111     //Dispatch_async (dispatch_get_global_queue (dispatch_queue_priority_default, 0), ^{ the     //[Self performselector: @selector (Run) Withobject:nil afterdelay:2.0];113     //    }); the     //1. Global Concurrency Queue thedispatch_queue_t queue = Dispatch_get_global_queue (Dispatch_queue_priority_default,0); the     117     //2. Calculate time for task execution118dispatch_time_t when = Dispatch_time (Dispatch_time_now, (int64_t) (5.0*nsec_per_sec));119      -     //3. The task in the queue will be executed at this point in time121Dispatch_after (when, queue, ^{122NSLog (@"----Run----%@", [Nsthread CurrentThread]);123     });124 } the 126@end

iOS multithreaded GCD Group