NSTimer定时器的用法

#import "ViewController.h"

@interface ViewController ()

{

    NSTimer *countDownTimer;

    int countDownTime;

}

@property (weak, nonatomic) IBOutlet UIButton *codeBtn;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

- (IBAction)getCodeBtnClick:(UIButton *)sender {

    [_codeBtn setEnabled:NO];

    if (countDownTimer)

    {

        [countDownTimer invalidate];

        countDownTimer=nil;

    }

    countDownTime=;

    countDownTimer=[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countDown) userInfo:nil repeats:YES];

}

-(void)countDown

{

    countDownTime--;

    if (countDownTime==)

    {

        [countDownTimer invalidate];

        countDownTimer=nil;

        [_codeBtn setEnabled:YES];

        [_codeBtn setTitle:@"获取验证码" forState:UIControlStateNormal];

        return;

    }

    NSString *count=[NSString stringWithFormat:@"%d",countDownTime];

    NSMutableAttributedString *attributeString=[[NSMutableAttributedString alloc]initWithString:[NSString stringWithFormat:@"剩余%@秒",count]];

    [attributeString addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(,count.length)];

    [_codeBtn setAttributedTitle:attributeString forState:UIControlStateDisabled];

}