【代碼筆記】iOS-performSelectorOnMainThread

代碼：

RootViewController.h

#import <UIKit/UIKit.h>

@interface RootViewController : UIViewController
{
    UILabel *label;
}

@end

RootViewController.m

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.title=@"performSelectorOnMainThread";
    
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    // performSelectorOnMainThread的作用就如其名，是在主線程執行某個selector， 所有的UIKit里的調用必須是在主線程的，在非主線程調用會產生非預期的結果也很可能會造成crash,所以當你在其他線程想執行一段UI調用的代碼時，就需要用到這個方法了
    
    [self performSelectorOnMainThread:@selector(loadData) withObject:nil waitUntilDone:NO];
    
}
-(void)loadData
{
    if (!label) {
        label=[[UILabel alloc]init];
        label.frame=CGRectMake(50, 80, 200, 200);
        label.backgroundColor=[UIColor redColor];
        [self.view addSubview:label];
    }else
    {
        [label removeFromSuperview];
        label=nil;
    }
    
}