网络多线程 ---实现网络负载图片

案例要求：网络负载图片，随机装上树立了良好的视图

实现的效果图例如以下：







详细代码例如以下：

//

// ViewController.m

// 0603---NSOperationQueue

#import "ViewController.h"

@interface
ViewController ()

@property (nonatomic,strong)
NSMutableArray * imageArray;

@end

@implementation ViewController

#pragma mark - 懒载入

- (NSMutableArray *)imageArray

{

if (_imageArray==nil)

{

_imageArray=[NSMutableArray
array];

}

return
_imageArray;

}

#pragma mark - 入口

- (void)viewDidLoad {

[super
viewDidLoad];

//载入视图

[self
_loadViews];

//开启多线程载入图片

[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> 採用NSOperation的子类NSInvocationOperation来开启多线程（必须加入到队列）

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

[queue
addOperation:nvo];

// 2> 採用NSBlockOperation
来开启多线程（必须加入到队列）

NSBlockOperation * block=[NSBlockOperation
blockOperationWithBlock:^{

NSLog(@"我是block");

}];

[queue
addOperation:block];

// 3> 採用队列（不须又一次加入到队列）

[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.指定线程的运行顺序- - - 依赖(addDependency)

//创建block1

NSBlockOperation * block1=[NSBlockOperation blockOperationWithBlock:^{

NSLog(@"我是block1");

}];

[queue addOperation:block1]; //加入到队列

//创建block2

NSBlockOperation * block2=[NSBlockOperation blockOperationWithBlock:^{

NSLog(@"我是block2");

}];

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

[queue addOperation:block2]; //加入到队列

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];