帮助倒计时应用程序。 [英] Help with a countdown app.

问题描述

我正在尝试做两件事：

在圣诞节那天，每当导航到页面时都会调用一个方法。

On Christmas day, invoke a method whenever the page is navigated to.

圣诞节过后，将christmasDay DateTime设置为+1年（因此倒计时"重置"）。

After Christmas day, set the christmasDay DateTime to +1 year (so the countdown "resets").

这是我的代码：

private void OnTick(object sender, EventArgs e)
        {
            DateTime christmasDay;
            DateTime.TryParse("11/17/13", out christmasDay);
            var timeLeft = christmasDay - DateTime.Now;


            int x = DateTime.Now.Year - christmasDay.Year;
            if (DateTime.Now > christmasDay)
            {
                if (x == 0)
                    x += 1;
                christmasDay.AddYears(x);
                if (DateTime.Now.Month == christmasDay.Month && DateTime.Now.Day == christmasDay.Day)
                {
                    itsChristmas();
                }
            }
            
             countdownText.Text = String.Format("{0:D2} : {1:D2} : {2:D2} : {3:D2}", timeLeft.Days, timeLeft.Hours, timeLeft.Minutes, timeLeft.Seconds);
        }

当我将日期设置为TODAY时，"itsChristmas（）"方法有效...但我实际上并不希望在倒计时的每个刻度上调用它。我尝试将它放在页面的构造函数中，但这不起作用。有什么想法吗？

When I set the date to TODAY, the "itsChristmas()" method works...but I don't actually want it to be invoked on each tick of the countdown. I tried putting it in the constructor of the page but that doesn't work. Any ideas?

第二个问题是，如果我将日期设置为今天前一天，它会给出负数。我不知道我的代码发生了什么问题。 ：（

The second problem is that if I set the date to a day before today, it gives me negative numbers. I don't know what is wrong with my code that this is happening. :(

推荐答案

你'如果你已经调用了今年的圣诞节功能，那么很可能必须在隔离存储器中存储一个标志。我将保存最后一次将圣诞节功能称为日期时间。

You'll most likely have to store a flag in isolated storage to set if you've already called the Christmas function for this year.  I'd save the last time the Christmas function was called as a DateTime.

这可能有用。 ：

This may work. :

// I'll use Dec 25 for my Christmas countdown...
DateTime nextChristmas = new DateTime(DateTime.Year(), 12, 25);

if(DateTime.Now.Date == nextChristmas.Date && ReadIsolatedStorageDate() != DateTime.Now.Date)
{
     SaveIsolatedStorageDate(DateTime.Now.Date);
     itsChristmas();
}
else if(DateTime.Now.Date == nextChristmas.Date)
    nextChristmas = new DateTime(DateTime.Now.Year+1, 12, 25);

// this contains the time remaining until this Christmas, or next Christmas, depending.
TimeSpan countdown = nextChristmas - DateTime.Now;

ReadIsol atedStorageDate和SaveIsolatedStorageDate函数留给您自己的练习，但只保存或加载传递的日期和时间。

The ReadIsolatedStorageDate and SaveIsolatedStorageDate functions are left for your own exercise, but just save or load the dates and times passed.

ie：

DateTime ReadIsolatedStorageDate();
{
}

和

void SaveIsolatedStorageDate(DateTime date)
{
}

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