关闭ViewController后如何继续倒数计时器 [英] How to continue the countdown timer after closing ViewController

问题描述

我使用UIDatePicker来实现倒数计时器.加载视图后datePickerMode设置CountDownTimer:

I use UIDatePicker to implement a countdown timer.After loading viewdatePickerMode set CountDownTimer:

- (void)viewDidLoad {
[super viewDidLoad];
self.countDownTimer.datePickerMode=UIDatePickerModeCountDownTimer;
}

首先在UIDatePicker中设置倒计时时间，然后按下按钮开始倒计时:

First,set the countdown time in UIDatePicker,then press the button to start the countdown:

- (IBAction)StartCountdown:(id)sender {
    [sender setTitle:@"Cancel" forState:UIControlStateNormal];
    countDownInterval = (NSTimeInterval)countDownTimer.countDownDuration;
    remainder = countDownInterval;
    afterRemainder = countDownInterval - remainder % 60 ;
    //call updateCountDown()
    timer=[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateCountDown) userInfo:nil repeats:YES];
}

调用updateCountDown():

-(void)updateCountDown{
    afterRemainder --;
    int hours = (int)(afterRemainder/(60*60));
    int mins = (int)(((int)afterRemainder/60)-(hours * 60));
    int secs = (int)(((int)afterRemainder - (60 * mins) - (60 * hours *60)));
    NSString *displayText = [[NSString alloc]initWithFormat:@"%02u : %02u : %02u",hours,mins,secs];
    self.displayLabel.text = displayText;
}

Action 可以正常执行，但是当我跳出这个视图并且不会执行 timer 为零时，我如何操作 timer 可以在跳转视图后持续?

Action can execute properly, but when I jump out of this view and will not perform timer is zero, how do I operate the timer can be sustained after the jump view?

推荐答案

我认为你可以:

1. 当你跳出视图时，让此时的状态保存到 NSUserDefaults
   • 剩余时间，可能以秒为单位
   • 当时的当前系统时间，考试时间:13:20:15

• 获取当前系统时间，将其与保存的系统时间(A)相结合
• 用 (A) 子保存剩余时间(以秒为单位)并继续倒计时.

只是一个想法，但希望它有所帮助

Just a idea, but hope it helps

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