IOSGCD Communication in a thread

Today let's look at how the iOS thread communicates.

#import "ViewController.h"

@interface viewcontroller ()

{

uiimageview *_image;

}

@end

@implementation Viewcontroller

-(void) viewdidload {

[superviewdidload];

cgrect frame = [[uiscreen mainscreen] bounds ];

_image = [[uiimageviewalloc]init];

_image. Frame = CGRectMake (0,0, frame. ) size . width , frame. size . Height - - );

[self. View addsubview:_image];

}

// when the user touches the screen, open a thread, download the picture

-(void) Touchesbegan: ( Nsset *) touches withevent: (uievent *) Event

{

[self performselectorinbackground: @selector ( Downloadimage)withobject:nil];

}

// sub-thread tasks, responsible for downloading picture resources in the network

-(void) downloadimage

{

//1. constructs a picture resource URL

nsurl *url = [nsurlurlwithstring:@ "/http/ C.hiphotos.baidu.com/image/pic/item/e61190ef76c6a7ef2469025dfefaaf51f3de667a.jpg "];

//2. Download Image

nsdata *data = [nsdatadatawithcontentsofurl : url];

//3. the binary Data Convert to Picture object

UIImage *image = [UIImageimagewithdata:d ATA];

// in iOS development, The action to update the UI must be put down in the main thread to execute

[_imageperformselectoronmainthread:@selector( SetImage:)withobject: Image waituntildone:NO];

    

}

// give the downloaded image to Uiimageview

-(void) setimage: ( UIImage *) Image

{ _image. Image = image;

}

@end

This is the way of communication in the thread, when the user touches this screen, it opens a thread to perform the download task, the download completes, takes the main thread to download the good picture to Uiimageview.

IOSGCD Communication in a thread