网络多线程 ---实现网络加载图片

案例要求：网络加载图片，随机加载到设置好的视图上

实现的效果图如下：







具体代码如下：

//

// ViewController.m

// 0603---NSOperationQueue

#import "ViewController.h"

@interface
ViewController ()

@property (nonatomic,strong)
NSMutableArray * imageArray;

@end

@implementation ViewController

#pragma mark - 懒加载
- (NSMutableArray *)imageArray
{

if (_imageArray==nil)
{

_imageArray=[NSMutableArray
array];
}

return
_imageArray;
}

#pragma mark - 入口
- (void)viewDidLoad {

[super
viewDidLoad];

//加载视图

[self
_loadViews];

//开启多线程加载图片

[self
_loadThread];

}

- (void)_loadViews
{

for (int i=0; i<15; i++)
{

int col=i%3;

int row=i/3;

UIImageView * imageView=[[UIImageView
alloc]initWithFrame:CGRectMake(22+col*(80+45),
40+row*(100+20),
90, 90)];
imageView.backgroundColor=[UIColor
redColor];
[self.imageArray
addObject:imageView];
[self.view
addSubview:imageView];
}
}

- (void)_loadThread
{

//开启多线程

NSOperationQueue * queue=[[NSOperationQueue
alloc]init];

for(int i=0;i<self.imageArray.count;i++)
{

NSBlockOperation * block=[NSBlockOperation
blockOperationWithBlock:^{

//下载图片

NSString * imageSrc=@"http://images.cnblogs.com/cnblogs_com/kenshincui/613474/o_%d.jpg";

imageSrc=[NSString
stringWithFormat:imageSrc,i];
//拼接字符串

NSURL * URL = [NSURL
URLWithString:imageSrc];

NSData * data = [NSData
dataWithContentsOfURL:URL];

UIImage * image=[UIImage
imageWithData:data];

//获取主线程，刷新UI

NSOperationQueue * queue2=[NSOperationQueue
mainQueue];
[queue2
addOperationWithBlock:^{

//刷新图片，给imageView赋值

UIImageView * imageView=self.imageArray[i];
imageView.image=image;

}];

}];
[queue
addOperation:block];
}

}

@end

0602---小结：

多线程的三种创建方式
NSThread

1.实例方法：（调用start方法开启多线程）
[NSThread alloc]initWithTarget:nil selector:nil withObject:nil];

2.类方法
[NSThread detachNewThreadSelector:nil toTarget:nil withObject:nil];

3.刷新UI必须通过主线程
[self performSelectorOnMainThread:nil withObject:nil waitUntilDone:nil];

(*)4.隐式开启多线程
[self performSelectorInBackground:nil withObject:nil];

0603- - - -NSOperationQueue

1.有对象方法，没有类方法

创建多线程（4种方式）:

// 1> 采用NSOperation的子类NSInvocationOperation来开启多线程（必须添加到队列）

NSInvocationOperation * nvo=[[NSInvocationOperation
alloc]initWithTarget:self
selector:@selector(show)
object:nil];
[queue
addOperation:nvo];

// 2> 采用NSBlockOperation
来开启多线程（必须添加到队列）

NSBlockOperation * block=[NSBlockOperation
blockOperationWithBlock:^{

NSLog(@"我是block");
}];
[queue
addOperation:block];

// 3> 采用队列（不须重新添加到队列）

[queue addOperationWithBlock:^{

NSLog(@"我是queue创建的block");
}];

// 4>

NSBlockOperation * block=[NSBlockOperation
blockOperationWithBlock:^{

NSLog(@"NSBlockOperation");
}];

[block addExecutionBlock:^{

NSLog(@"NSBlockOperation===1");
}];

[block addExecutionBlock:^{

NSLog(@"NSBlockOperation===2");
}];

[block addExecutionBlock:^{

NSLog(@"NSBlockOperation===3");
}];

[block
start];

2.指定线程的执行顺序- - - 依赖(addDependency)

//创建block1

NSBlockOperation * block1=[NSBlockOperation blockOperationWithBlock:^{

NSLog(@"我是block1");

}];

[queue addOperation:block1]; //添加到队列

//创建block2

NSBlockOperation * block2=[NSBlockOperation blockOperationWithBlock:^{

NSLog(@"我是block2");

}];

[block2 addDependency:block1]; //依赖---先后执行顺序（block1 > block2）

[queue addOperation:block2]; //添加到队列

3.刷新UI

//开启多线程

NSOperationQueue * queue=[[NSOperationQueue
alloc]init];

NSBlockOperation * block=[NSBlockOperation
blockOperationWithBlock:^{

//下载图片

{

}

//获取主线程，刷新UI

NSOperationQueue * queue2=[NSOperationQueue
mainQueue];

[queue2 addOperationWithBlock:^{

//刷新图片，给imageView赋值

{

}

}];
}];
[queue
addOperation:block];