#import <UIKit/UIKit.h>

@interface RootViewController : UIViewController
{
    //定义定时器
    NSTimer *timer;
}
@end

-(void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    
    //重新开启定时器
    [timer setFireDate:[NSDate distantPast]];
    
}
-(void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    
    // 暂时关闭定时器。
    [timer  setFireDate:[NSDate distantFuture]];
}


- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.title=@"定时器的使用";
    //当在有定时器的页面时，定时器是启动的。当离开定时器所在的页面时，定时器停止，当在次地进入时，定时器重新启动。
    
    
    //定时器函数。
    timer=[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(loadData) userInfo:nil repeats:YES];
    
}
-(void)loadData
{
    NSLog(@"I Love You!");
}