Changing the span of CollectionView while rotating phone isn't working

Question

I'm trying to change the span of CollectionView while rotating my iPhone. To make it easy, just show 2 columns in portrait, and 4 columns in landscape. It works when rotating from portrait to landscape mode, but when rotating back to portrait mode, it always shows 1 column. My code likes,

    VideoCollectionView = new CollectionView()
        {
            ItemsLayout = new GridItemsLayout(2, ItemsLayoutOrientation.Vertical),
        };
    ...

    private static double screen_width = 1280.0;
    private static double screen_height = 720.0;

    protected override void OnSizeAllocated(double width, double height)
    {
        base.OnSizeAllocated(width, height);

        if ((Math.Abs(screen_width - width) > minimum_double) || (Math.Abs(screen_height - height) > minimum_double))
        {
            screen_width = width;
            screen_height = height;

            int split;
            if (screen_width > screen_height)
            {   // landscape mode
                split = 4;
            }
            else
            {   // portrait mode
                split = 2;
            }

            VideoCollectionView.ItemsLayout = new GridItemsLayout(split, ItemsLayoutOrientation.Vertical);
        }
    }

Is this a bug? Or I should use other ways? Thanks for help.

Answer 1

You could use a Singleton for storing the current orientation.Because it is unwise to set the screen size as s static value . It maybe will cause issue on different size of device .

public class CurrentDevice
{
    protected static CurrentDevice Instance;
    double width;
    double height;

    static CurrentDevice()
    {
        Instance = new CurrentDevice();
    }
    protected CurrentDevice()
    {
    }

    public static bool IsOrientationPortrait()
    {
        return Instance.height > Instance.width;
    }

    public static void SetSize(double width, double height)
    {
        Instance.width = width;
        Instance.height = height;
    }
}

And in the method

protected override void OnSizeAllocated(double width, double height)
{
   base.OnSizeAllocated(width, height);


   if (CurrentDevice.IsOrientationPortrait() && width > height || !CurrentDevice.IsOrientationPortrait() && width < height)
   {
      int split;
      CurrentDevice.SetSize(width, height);

      // Orientation got changed! Do your changes here
      if (CurrentDevice.IsOrientationPortrait())
      {
         // portrait mode
         split = 2;
      }

      else
      {
         // landscape mode
         split = 4;
      }

      VideoCollectionView.ItemsLayout = new GridItemsLayout(split, ItemsLayoutOrientation.Vertical);
   }


}