IOS多线程 使用线程加载一张图片 NSThread(1)

更新UI的操作在IOS中其实和在Android中是一致的，都是不能在主线程中执行比较耗时的操作，所以需要开启新线程去做这些操作，以免阻塞主线程，当新线程中的操作完成之后，调用主线程来更新UI。下面就是一个这样的例子：

1、声明ImageView控件

#import <UIKit/UIKit.h>

@interface DemoDispatchQueueViewController : UIViewController
@property(nonatomic,strong) UIImageView *imageView;
@end

2、完成功能

#import "DemoDispatchQueueViewController.h"

@interface DemoDispatchQueueViewController ()

@end

@implementation DemoDispatchQueueViewController
@synthesize imageView;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.title = @"GCD Demo";
    
    self.imageView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 300, 380)];
    
    self.imageView.contentMode = UIViewContentModeScaleToFill;
    
    [self.view addSubview:imageView];
    
    [NSThread detachNewThreadSelector:@selector(loadImageByUrl:) toTarget:self withObject:@"http://image.rayliimg.cn/0008/2009-01-15/images/2009115135825184.jpg"];
    
}

-(void) loadImageByUrl:(NSString *) imageUrl
{
    NSLog(@"url is :%@",imageUrl);
    NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:imageUrl]];
    UIImage *image = [UIImage imageWithData:data];
    
    if(image != nil){
        [self performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:YES];
    }else{
        NSLog(@"无法载入相应的图片");
    }
}
-(void) setImage:(UIImage*) image{
    [self.imageView setImage:image];
}


- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end