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=; 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=;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];
原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/3370.html