网络多线程 ---实现网络加载图片

来源：互联网发布：航天科技知乎编辑：程序博客网时间：2024/05/23 00:47

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=[NSMutableArrayarray];

}

return_imageArray;

}

#pragma mark - 入口

- (void)viewDidLoad {

[superviewDidLoad];

//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=[[UIImageViewalloc]initWithFrame:CGRectMake(22+col*(80+45),40+row*(100+20),90, 90)];

imageView.backgroundColor=[UIColorredColor];

[self.imageArrayaddObject:imageView];

[self.viewaddSubview:imageView];

}

- (void)_loadThread

{

//开启多线程

NSOperationQueue * queue=[[NSOperationQueuealloc]init];

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

{

NSBlockOperation * block=[NSBlockOperationblockOperationWithBlock:^{

//下载图片

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

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

NSURL * URL = [NSURLURLWithString:imageSrc];

NSData * data = [NSDatadataWithContentsOfURL:URL];

UIImage * image=[UIImageimageWithData:data];

//获取主线程，刷新UI

NSOperationQueue * queue2=[NSOperationQueuemainQueue];

[queue2addOperationWithBlock:^{

//刷新图片，给imageView赋值

UIImageView * imageView=self.imageArray[i];

imageView.image=image;

}];

[queueaddOperation: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=[[NSInvocationOperationalloc]initWithTarget:selfselector:@selector(show)object:nil];

[queueaddOperation:nvo];

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

NSBlockOperation * block=[NSBlockOperationblockOperationWithBlock:^{

NSLog(@"我是block");

}];

[queueaddOperation: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=[NSBlockOperationblockOperationWithBlock:^{

NSLog(@"NSBlockOperation");

}];

[block addExecutionBlock:^{

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

}];

[block addExecutionBlock:^{

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

}];

[block addExecutionBlock:^{

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

}];

[blockstart];

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=[[NSOperationQueuealloc]init];

NSBlockOperation * block=[NSBlockOperationblockOperationWithBlock:^{

//下载图片

{

}

//获取主线程，刷新UI

NSOperationQueue * queue2=[NSOperationQueuemainQueue];

[queue2 addOperationWithBlock:^{

//刷新图片，给imageView赋值

{

}

}];

[queueaddOperation:block];

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