Basic iosGCD usage

Basic iosGCD usage

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# Import "ViewController. h"

 

@ Interface ViewController ()

{

 

UIImageView * _ view;

}

@ End

 

@ Implementation ViewController

 

-(Void) viewDidLoad {

[Super viewDidLoad];

 

 

// The main queue column is a queue associated with the main thread. The main queue column is a special queue provided by GCD. Tasks added to the main queue column are executed in the main thread. Note: No threads are created for adding tasks to the main queue, whether synchronous or asynchronous.

// Dispatch_get_main_queue (); Method for retrieving the main queue Column

 

// Enable the sub-thread to call the test method

[Self defined mselectorinbackground: @ selector (test) withObject: nil];

 

 

_ View = [[UIImageView alloc] init];

_ View. frame = CGRectMake (0, 0, self. view. bounds. size. width, 300 );

[Self. view addSubview: _ view];

 

 

 

}

 

-(Void) test

{

 

Dispatch_queue_t queue = dispatch_queue_create ("Concurrent Queue", DISPATCH_QUEUE_CONCURRENT );

 

Dispatch_async (queue, ^ {

NSLog (@ "222 curThread = % @", [NSThread currentThread]);

});

 

 

Dispatch_sync (queue, ^ {

NSLog (@ "333 cureThread = % @", [NSThread currentThread]);

});

 

}

 

 

 

// Click the screen to download an image from the network and display it on the interface.

-(Void) touchesBegan :( NSSet *) touches withEvent :( UIEvent *) event

{

 

// 1. Retrieve global queue

Dispatch_queue_t queue = dispatch_get_global_queue (DISPATCH_QUEUE_PRIORITY_DEFAULT, 0 );

// Add the image download task to the parallel queue

Dispatch_async (queue, ^ {

 

 

NSLog (@ "1111: curThread = % @", [NSThread currentThread]);

 

NSURL * url = [NSURL URLWithString: @ "http://h.hiphotos.baidu.com/image/pic/item/35a85edf8db1cb13966db40fde54564e92584ba2.jpg"];

 

NSData * data = [NSData dataWithContentsOfURL: url];

 

UIImage * image = [UIImage imageWithData: data];

 

 

// Use GCD to set the image to be displayed in the main thread.

// Benefit: Resources in the subthread can be directly used in the main thread. Easy to use and intuitive.

// The operation ui is executed in the main thread

Dispatch_async (dispatch_get_main_queue (), ^ {

_ View. image = image;

});

 

 

});

 

 

 

 

}

 

 

-(Void) test11

{

// Dispatch_queue_t queue = dispatch_get_global_queue (<# long identifier #>,< # unsigned long flags #>)

Dispatch_queue_t queue = dispatch_queue_create ("Concurrent Queue", DISPATCH_QUEUE_CONCURRENT );

 

Dispatch_async (queue, ^ {

 

// Perform time-consuming operations

 

Dispatch_async (dispatch_get_main_queue (), ^ {

// Operation UI

});

});

}

@ End