#define global_queue dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)

#define main_queue dispatch_get_main_queue()

#import "HMViewController.h"

@interface HMViewController ()

@property (weak, nonatomic) IBOutlet UIImageView *imageView1;

@property (weak, nonatomic) IBOutlet UIImageView *imageView2;

@property (weak, nonatomic) IBOutlet UIImageView *bigImageView;

@end

@implementation HMViewController

- (void)viewDidLoad

{

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    // 图片1: http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg

    // 图片2: http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg

    /**

     1.下载图片1和图片2

     2.将图片1和图片2合并成一张图片后显示到imageView上

     思考:

     * 下载图片 : 子线程

     * 等2张图片都下载完毕后, 才回到主线程

     */

}

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

{

    // 创建一个组

    dispatch_group_t group = dispatch_group_create();

    // 开启一个任务下载图片1

    __block UIImage *image1 = nil;

    dispatch_group_async(group, global_queue, ^{

        image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];

    });

    // 开启一个任务下载图片2

    __block UIImage *image2 = nil;

    dispatch_group_async(group, global_queue, ^{

        image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/b2a9cfc88b7a56cfa59b8d09208fa1fb.jpg"];

    });

    // 同时执行下载图片1\下载图片2操作

    // 等group中的所有任务都执行完毕, 再回到主线程执行其他操作

    dispatch_group_notify(group, main_queue, ^{

        self.imageView1.image = image1;

        self.imageView2.image = image2;

        // 合并

        UIGraphicsBeginImageContextWithOptions(CGSizeMake(, ), NO, 0.0);

        [image1 drawInRect:CGRectMake(, , , )];

        [image2 drawInRect:CGRectMake(, , , )];

        self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext();

        // 关闭上下文

        UIGraphicsEndImageContext();

    });

//    if (self.log == NO) {

//        NSLog(@"-------touchesBegan");

//        self.log = YES;

//    }

//    static dispatch_once_t onceToken;

//    dispatch_once(&onceToken, ^{

//        NSLog(@"-------touchesBegan");

//    });

}

- (void)downlaod2image

{

    dispatch_async(global_queue, ^{

        NSLog(@"下载图片---%@", [NSThread currentThread]);

        // 下载图片1

        UIImage *image1 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];

        NSLog(@"下载完图片1---%@", [NSThread currentThread]);

        // 下载图片2

        UIImage *image2 = [self imageWithURL:@"http://news.baidu.com/z/resource/r/image/2014-06-22/2a1009253cf9fc7c97893a4f0fe3a7b1.jpg"];

        NSLog(@"下载完图片2---%@", [NSThread currentThread]);

        dispatch_async(main_queue, ^{

            NSLog(@"显示图片---%@", [NSThread currentThread]);

            self.imageView1.image = image1;

            self.imageView2.image = image2;

            // 合并

            UIGraphicsBeginImageContextWithOptions(CGSizeMake(, ), NO, 0.0);

            [image1 drawInRect:CGRectMake(, , , )];

            [image2 drawInRect:CGRectMake(, , , )];

            self.bigImageView.image = UIGraphicsGetImageFromCurrentImageContext();

            // 关闭上下文

            UIGraphicsEndImageContext();

        });

    });

}

- (UIImage *)imageWithURL:(NSString *)urlStr

{

    NSURL *url = [NSURL URLWithString:urlStr];

    NSData *data = [NSData dataWithContentsOfURL:url]; // 这行会比较耗时

    return [UIImage imageWithData:data];

}

- (void)delay

{

    //    NSLog(@"----touchesBegan----%@", [NSThread currentThread]);

    //    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

    //        [self performSelector:@selector(run) withObject:nil afterDelay:2.0];

    //    });

    // 1.全局并发队列

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, );

    // 2.计算任务执行的时间

    dispatch_time_t when = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5.0 * NSEC_PER_SEC));

    // 3.会在when这个时间点, 执行queue中的任务

    dispatch_after(when, queue, ^{

        NSLog(@"----run----%@", [NSThread currentThread]);

    });

}

//- (void)run

//{

//    NSLog(@"----run----%@", [NSThread currentThread]);

//}

@end