GCD调度组、自定义队列来实现多个下载任务

发布于:2021-10-21 20:22:54

#define KURL1 @"http://img0.imgtn.bdimg.com/it/u=79920747,2237302485&fm=90&gp=0.jpg"
#define KURL2 @"http://img5.imgtn.bdimg.com/it/u=2983485216,1361143125&fm=90&gp=0.jpg"
#import "ViewController.h"

@interface ViewController ()
{
dispatch_queue_t myQueue;
}
@property (weak, nonatomic) IBOutlet UILabel *remindLabel;
@property (weak, nonatomic) IBOutlet UIImageView *firstImageView;
@property (weak, nonatomic) IBOutlet UIImageView *secondImageView;

@end

@implementation ViewController

- (void)viewDidLoad
{
[super viewDidLoad];
//自定义队列
myQueue=dispatch_queue_create("myQueue", DISPATCH_QUEUE_CONCURRENT);
}


- (IBAction)sendBtnClick:(UIButton *)sender
{
//创建调度组
dispatch_group_t myGroup=dispatch_group_create();

//延时执行
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(NSEC_PER_SEC*2)), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
dispatch_group_async(myGroup, myQueue, ^{

dispatch_async(myQueue, ^{

NSData *firstData=[NSData dataWithContentsOfURL:[NSURL URLWithString:KURL1]];
//主队列刷新UI
dispatch_async(dispatch_get_main_queue(), ^{
_firstImageView.image=[UIImage imageWithData:firstData];

});

});
});

dispatch_group_async(myGroup, myQueue, ^{

dispatch_async(myQueue, ^{

NSData *secondData=[NSData dataWithContentsOfURL:[NSURL URLWithString:KURL2]];
//主队列刷新UI
dispatch_async(dispatch_get_main_queue(), ^{
_secondImageView.image=[UIImage imageWithData:secondData];

});

});

});

});

//异步函数监听调度组里面的任务完成后刷新UI
dispatch_group_notify(myGroup, myQueue, ^{
_remindLabel.text=@"下载完成";

});
/*
//同步函数 主线程阻塞 主要用于数据库操作
dispatch_group_wait(myGroup, dispatch_time(DISPATCH_TIME_NOW, (int64_t)(NSEC_PER_SEC)));
_remindLabel.text=@"下载完成";
*/
}

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转载于:https://www.cnblogs.com/thbbsky/p/4376338.html

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