#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!");

}