win8頁面導航--刪除當前頁面堆棧信息

win8中導航很容易，僅一行代碼就可實現，但是如果我不想讓某些頁面保存在導航堆棧中怎麼辦？微軟目前沒有提供這樣的功能。

  要想實現這樣的功能需要從堆棧歷史記錄下手，從farm.GetNavigationState()這個函數找到突破口。

  來看看farm.GetNavigationState()返回的信息格式：

  1,3,1,37,Page1,0,39,Page2,0,34,Page3,0

   第一個數字1和最後一個數字0是 固定格式，如果堆棧信息是空的，那麼堆棧的記錄就是“1，0”;

   第二個數字3代表當前堆棧中頁面的個數;

   第三個數字1則是當前顯示的頁面在堆棧中的索引;

   第四個數字37暫時理解成頁面的ID吧;

   第五個則是頁面名稱了;

  所以堆棧的格式如下

  1，頁面數量，當前頁面索引，頁面1ID,頁面1名稱，0，頁面2ID,頁面2名稱，...，0

  瞭解堆棧格式就好辦了，開始按照我們的需求寫代碼吧。

   首先我想把當前頁面信息從堆棧中刪除，代碼如下：

  public static void RemoveCurrent(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm == null) return;

            string navigationHistory = farm.GetNavigationState();

            List<string> history = new List<string>(navigationHistory.Split(','));

            if (history.Count <= 2) return;

            history.RemoveRange(history.Count - 2, 2);

            int numberOfPages = int.Parse(history[1]);
            int currentPageIndex = int.Parse(history[2]);

            numberOfPages--;
            currentPageIndex--;

            history[1] = numberOfPages.ToString();
            history[2] = currentPageIndex.ToString();

            string newHistory = String.Join<string>(",", history.AsEnumerable());

            farm.SetNavigationState(newHistory);                

        }

   使用的時候像這樣this.Frame.RemoveCurrent();就可以了

    那麼清空我要清空整個堆棧信息呢?看下面代碼：

   

public static void ClearAll(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm != null)
                farm.SetNavigationState("1,0");
        }

    調用方法同上this.Frame.ClearAll();

    整個導航工具的代碼：

 public static class NavigateStackUtil
    {
        public static void ClearAll(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm != null)
                farm.SetNavigationState("1,0");
        }

        public static void RemoveCurrent(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm == null) return;

            string navigationHistory = farm.GetNavigationState();

            List<string> history = new List<string>(navigationHistory.Split(','));

            if (history.Count <= 2) return;

            history.RemoveRange(history.Count - 2, 2);

            int numberOfPages = int.Parse(history[1]);
            int currentPageIndex = int.Parse(history[2]);

            numberOfPages--;
            currentPageIndex--;

            history[1] = numberOfPages.ToString();
            history[2] = currentPageIndex.ToString();

            string newHistory = String.Join<string>(",", history.AsEnumerable());

            farm.SetNavigationState(newHistory);                

        }

        public static void GoBack(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm != null && farm.CanGoBack) farm.GoBack();
        }

        public static void GoForward(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm != null && farm.CanGoBack) farm.GoForward();
        }

        public static void GoHome(this Frame farm)
        {
            if (farm == null)
                farm = Window.Current.Content as Frame;

            if (farm == null) return;

            string navigationHistory = farm.GetNavigationState();

            List<string> history = new List<string>(navigationHistory.Split(','));

            if (history.Count <= 6) return;

            history.RemoveRange(6, history.Count-6);

            history[1] = "1";
            history[2] = "0";

            string newHistory = String.Join<string>(",", history.AsEnumerable());

            farm.SetNavigationState(newHistory);                

        }
    }

  歡迎大家多多交流。