[消息传递之四]－NSTimer练习倒计时

ゞ浴缸里的玫瑰 2022-08-19 08:59 190阅读 0赞

#import <UIKit/UIKit.h>
    
    @interface ViewController : UIViewController<UIAlertViewDelegate>
    
    @property (strong, nonatomic) IBOutlet UILabel *labTime;
    - (IBAction)btnStart:(UIButton *)sender;
    
    - (IBAction)btnStop:(UIButton *)sender;
    @property (strong, nonatomic) IBOutlet UIButton *btnS;
    @property (strong, nonatomic) IBOutlet UIButton *btnE;
    
    @end

#import "ViewController.h"
    
    @interface ViewController ()
    
    @end
    
    @implementation ViewController
    {
        NSInteger iValue;
        NSTimer* t;
    }
    
    - (void)viewDidLoad {
        NSDate* d = [NSDate distantFuture];
        NSNumber* n = [NSNumber numberWithInteger:100];
        iValue = 5;
        SEL e =@selector(TestTimerSEL:);
        t = [[NSTimer alloc] initWithFireDate:d interval:1 target:self selector:e userInfo:n repeats:YES];
        [[NSRunLoop currentRunLoop] addTimer:t forMode:NSDefaultRunLoopMode];
        [super viewDidLoad];
        // Do any additional setup after loading the view, typically from a nib.
    }
    
    -(void)TestTimerSEL:(id)Sender
    {
        iValue--;
        self.labTime.text = [NSString stringWithFormat:@"%ld",iValue];
        NSInteger param = [[Sender userInfo] integerValue];
        NSLog(@"This is %ld times, sender is %ld", iValue, param);
        if (iValue == 0) {
            UIAlertView* view = [[UIAlertView alloc] initWithTitle:@"提示" message:@"时间到" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];
            [view show];
            [t invalidate];
        }
        
    }
    - (void)didReceiveMemoryWarning {
        [super didReceiveMemoryWarning];
        // Dispose of any resources that can be recreated.
    }
    
    - (IBAction)btnStart:(UIButton *)sender {
        [t setFireDate:[NSDate date]];
        [self.btnS setEnabled:NO];
        [self.btnE setEnabled:YES];
        [self.btnS setTitle:@"继续" forState:UIControlStateNormal];
    }
    
    - (IBAction)btnStop:(UIButton *)sender {
        [self.btnS setEnabled:YES];
        [self.btnE setEnabled:NO];
        [t setFireDate:[NSDate distantFuture]];
    }
    @end

1，nstimer的暂停和继续是利用setfiredate来实现，退出执行是invalidate;

2，nstimer还有一个初始化方式是scheduled，直接放到runloop里面。

3，固定的执行sel格式，其中sender为timer自己，userinfo为参数。