@interface ViewController ()
/* 圖片視圖/
@property(nonatomic,weak) UIImageView * imageView;
/* 圖片數組/
@property(nonatomic,strong) NSMutableArray * imageArray;
/* 存儲線程/
@property(nonatomic,strong) NSMutableArray * threadArray;
@end
//對象方法cancle，可以在外部使用。
//類方法exit，寫在線程內部，結束當前現線程。
//兩者結合使用，使用cancle進行標記，使用exit退出
@implementation ViewController

(NSMutableArray *)imageArray

{

if (_imageArray==nil) {

    _imageArray =[NSMutableArray array];

}

return _imageArray;


}

(NSMutableArray *)threadArray

{

if (_threadArray==nil) {

    _threadArray =[NSMutableArray array];

}

return _threadArray;


}

(void)viewDidLoad

{

[super viewDidLoad];



//加載視圖

[self _loadViews];



//開啟多線程加載圖片

[self _openMultiThread];    


}
//======加載這個，可以在主線程中加載

(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];

}


//    添加按鈕

 UIButton * button=[UIButton buttonWithType:UIButtonTypeContactAdd];

 button.frame=CGRectMake(0, 20, 20, 20);

 [button addTarget:self action:@selector(btClick) forControlEvents:UIControlEventTouchUpInside];

 [self.view addSubview:button];    


}
//開啟多線程加載圖片

(void) _openMultiThread

{

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

{


//        [NSThread detachNewThreadSelector:@selector(loadImage:) toTarget:self withObject:@(i)];
//        要存數組就不能使用類方法創建線程

    NSThread * thread = [[NSThread alloc] initWithTarget:self selector:@selector(loadImage:) object:@(i)];

    [thread start];

    [self.threadArray addObject:thread];

}


}

(void)loadImage:(NSNumber *) number

{

//取到索引

NSInteger index=[number integerValue];



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



imageSrc=[NSString stringWithFormat:imageSrc,index];





NSURL * URL=[NSURL URLWithString:imageSrc];

NSData * data=[NSData dataWithContentsOfURL:URL];

UIImage *image=[UIImage imageWithData:data];



//封裝model

ImageModel * model=[[ImageModel alloc] init];

model.image=image;

model.index=index;




//如果狀態為刪除，則退出線程

NSThread * thread = [NSThread currentThread];

if ([thread isCancelled])

{

    [NSThread exit];//執行exit，后邊的語句不再執行。所以不用寫return

//return也可以退出進程，一旦退出就不能再使用start開啟

}

NSLog(@"%@", thread);

[self performSelectorOnMainThread:@selector(showImage:) withObject:model waitUntilDone:NO];


}
//回到主線程更新圖片

(void) showImage:(ImageModel *) model

{

UIImageView * imageView=self.imageArray[model.index];

imageView.image=model.image;


}
pragma mark - 點擊事件

(void)btClick

{
//    當點擊按鈕時，對所有線程進行標記

for (NSThread * t in self.threadArray)

{

    [t cancel];

}


}
</pre>