OC 线程操作3 - NSOperation 实现线程间通信

 #import "ViewController.h"

 @interface ViewController ()

 /**
  图片
  */
 @property (weak, nonatomic) IBOutlet UIImageView *imageView;

 @end

 @implementation ViewController
 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
 //    [self downloadImage];
     [self downloadImagAndCompoundIma];
 }

 /**
  下载图片 并且合成

  */
 -(void)downloadImagAndCompoundIma{

     /*
      获取图片属性1：搞两个属性 然后self.img1, self.img2
      获取图片属性2: 使用__blcok修饰，
      */
     __block UIImage *ima1 = [[UIImage alloc] init];
     __block UIImage *ima2 = [[UIImage alloc] init];

     //1.创建 非主队列
     NSOperationQueue *queue = [[NSOperationQueue alloc] init];

     //2.创建任务 : 下载图片1
     NSBlockOperation *op1 =  [NSBlockOperation blockOperationWithBlock:^{

         NSString *urlStr = [NSString stringWithFormat:@"http://pic.90sjimg.com/design/00/07/85/23/58ef8faf71ffe.png"];
         NSURL *url = [NSURL URLWithString:urlStr];
         NSData *data = [NSData dataWithContentsOfURL:url];
         ima1 = [UIImage imageWithData:data];
     }];

     //3.创建任务 : 下载图片2
     NSBlockOperation * op2 = [NSBlockOperation blockOperationWithBlock:^{
         // 下载图片
         NSString *urlStr = [NSString stringWithFormat:@"http://pic28.nipic.com/20130330/9607253_143631959000_2.png"];
         NSURL *url = [NSURL URLWithString:urlStr];
         NSData *data = [NSData dataWithContentsOfURL:url];
         ima2 = [UIImage imageWithData:data];
     }];

     //4.合成图片
     NSBlockOperation *op3 = [NSBlockOperation blockOperationWithBlock:^{
         //1。开启图形上下文 并且设置上下文 宽高
         UIGraphicsBeginImageContext(CGSizeMake(, ));

         //2.图片画图
         [ima1 drawInRect:CGRectMake(, , , )];
         ima1 = nil;

         [ima2 drawInRect:CGRectMake(, , , )];
         ima2 = nil;

         //3.根据图形上下文去图片
         UIImage *ima = UIGraphicsGetImageFromCurrentImageContext();

         //4.关闭上下文
         UIGraphicsEndImageContext();
         //3.回到主线程刷新UI
         [[NSOperationQueue mainQueue] addOperationWithBlock:^{
             self.imageView.image = ima;
         }];
     }];

     //5.添加依赖，因为全都是异步执行 谁先谁后不可控
     [op3 addDependency:op1];
     [op3 addDependency:op2];

     //3.添加任务
     [queue addOperation:op1];
     [queue addOperation:op2];
     [queue addOperation:op3];
 }


 /**
  下载图片

  */
 -(void)downloadImage{

     //1.创建 非主队列
     NSOperationQueue *queue = [[NSOperationQueue alloc] init];

     //2.创建任务
     NSBlockOperation *op1 =  [NSBlockOperation blockOperationWithBlock:^{

         //2.1 下载图片
         NSString *urlStr = [NSString stringWithFormat:@"http://pic.90sjimg.com/design/00/07/85/23/58ef8faf71ffe.png"];
         NSURL *url = [NSURL URLWithString:urlStr];
         NSData *data = [NSData dataWithContentsOfURL:url];
         UIImage *ima = [UIImage imageWithData:data];

         //3.回到主线程刷新UI
         [[NSOperationQueue mainQueue] addOperationWithBlock:^{
             self.imageView.image = ima;
         }];

     }];

     //3.添加任务
     [queue addOperation:op1];
 }
 @end