Question

我正在处理buzzer app for IOS。当您click the buzzer时，它会发出嗡嗡声，30 seconds会弹出，然后倒计时直至after 1，然后发出嗡嗡声并消失。如果在30-second countdown期间，有人想要重置蜂鸣器（以便计时器熄灭并消失），他们只需点击buzzer again。

我有三个问题：
的 1。如何在UILabel不可见的情况下启动应用程序，然后在第一次点击时显示？
的 2。如何在30秒倒计时期间点击蜂鸣器重置蜂鸣器？
第3。重置蜂鸣器会在多次点击时极其快速地解决定时器下降的问题吗？

viewcontrol.h

#import <UIKit/UIKit.h>
#import <AudioToolbox/AudioToolbox.h>

@interface ViewController : UIViewController {

    IBOutlet UILabel *seconds;
    NSTimer *timer;
    int MainInt;
    SystemSoundID buzzer;

}


- (IBAction)start:(id)sender;
- (void)countdown;

@end

ViewController.m #import＆＃34; ViewController.h＆＃34;

@interface ViewController ()

@end

@implementation ViewController


-(IBAction)start:(id)sender {
   seconds.hidden = NO;
   MainInt = 30;
   timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countdown) userInfo:nil repeats:YES];
AudioServicesPlaySystemSound(buzzer);

}


-(void)countdown {
    MainInt -= 1;
    seconds.text = [NSString stringWithFormat:@"%i", MainInt];
    if (MainInt < 1) {
        [timer invalidate];
        timer = nil;
        seconds.hidden = YES;
        AudioServicesPlaySystemSound(buzzer);
        }


}


- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    NSURL *buttonURL = [NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"Buzz" ofType:@"wav"]];
    AudioServicesCreateSystemSoundID((__bridge CFURLRef)buttonURL, &buzzer);
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Answer 1

1）在启动时隐藏标签

- (void)viewDidLoad
{

   [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    //hide the label initially
    [seconds setHidden:YES];

    /// other code

然后在start方法

中调用[seconds setHidden:NO];

2）重置蜂鸣器

-(IBAction)start:(id)sender {
   seconds.hidden = NO;
   MainInt = 30;

   if(timer != nil)
   {
      //timer exist..stop previous timer first.
     [timer invalidate];
   }

   timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countdown) userInfo:nil repeats:YES];
AudioServicesPlaySystemSound(buzzer);

}

Answer 2

1）如果标签在延迟时变得可见，请使用seconds.alpha = 0.0初始化标签（在代码或IB中）。然后让它可见......

NSTimeInterval delayUntilLabelIsVisible = 3.0;  // 3 seconds
[UIView animateWithDuration:0.3
                      delay:delayUntilLabelIsVisible
                    options:UIViewAnimationCurveEaseIn
                 animations:^{seconds.alpha = 1.0;}
                 completion:^(BOOL finished) {}];

2,3）您的第二个和第三个问题可以通过start方法中的一行代码解决...

-(IBAction)start:(id)sender {

   seconds.hidden = NO;
   MainInt = 30;

   // cancel the old timer before creating a new one
   // (otherwise many timers will run at once, calling the buzzer method too often)
   [timer invalidate];

   timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countdown) userInfo:nil repeats:YES];
    AudioServicesPlaySystemSound(buzzer);
}

重置计时器问题IOS

2 个答案: