ProfilePage.xaml.cs

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using System;
using Microsoft.Practices.ServiceLocation;
using PhotoSharingApp.Universal.Models;
using PhotoSharingApp.Universal.Serialization;
using PhotoSharingApp.Universal.Unity;
using PhotoSharingApp.Universal.ViewModels;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Navigation;

namespace PhotoSharingApp.Universal.Views
{
    /// <summary>
    /// The profile page that shows all uploaded photos of a user.
    /// </summary>
    public sealed partial class ProfilePage : BasePage
    {
        private static object _lastUsedNavigationArgs;
        private const int ItemMargin = 4;
        private const double PreferredImageWidth = 300;
        private Thickness _imageMargin;
        private double _imageWidth;
        private ProfileViewModel _viewModel;

        /// <summary>
        /// The constructor
        /// </summary>
        public ProfilePage()
        {
            InitializeComponent();

            UpdateImageWidth();

            SizeChanged += ProfilePage_SizeChanged;
        }

        /// <summary>
        /// The margin of each image control.
        /// </summary>
        public Thickness ImageMargin
        {
            get { return _imageMargin; }
            set
            {
                if (_imageMargin != value)
                {
                    _imageMargin = value;
                    NotifyPropertyChanged();
                }
            }
        }

        /// <summary>
        /// The width of each image control.
        /// </summary>
        public double ImageWidth
        {
            get { return _imageWidth; }
            set
            {
                if (Math.Abs(value - _imageWidth) >
                    AppEnvironment.FloatingComparisonTolerance)
                {
                    _imageWidth = value;
                    NotifyPropertyChanged();
                }
            }
        }

        protected override async void OnNavigatedTo(NavigationEventArgs e)
        {
            base.OnNavigatedTo(e);

            var navigationArgs = e.Parameter;

            // We only load data if we either navigate forwards or
            // if navigation parameters have changed (e.g. showing different user on profile page).
            var loadData = e.NavigationMode != NavigationMode.Back
                           || _lastUsedNavigationArgs != navigationArgs;

            _viewModel = ServiceLocator.Current.GetInstance<ProfileViewModel>(loadData);
            DataContext = _viewModel;

            if (loadData)
            {
                _lastUsedNavigationArgs = navigationArgs;

                if (navigationArgs != null)
                {
                    var profilePageNavigationArgs =
                        SerializationHelper.Deserialize<ProfileViewModelArgs>(navigationArgs as string);

                    await _viewModel.LoadState(profilePageNavigationArgs);
                }
                else
                {
                    await _viewModel.LoadState();
                }
            }
        }

        private void ProfilePage_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            UpdateImageWidth();
        }

        private void UpdateImageWidth()
        {
            if (pageRoot.ActualWidth < 720)
            {
                ImageWidth = pageRoot.ActualWidth;
                ImageMargin = new Thickness(0, 0, 0, 4);
            }
            else
            {
                // Calculating how many items per row we get with preferred with + image margin
                var itemsPerRow = (int) (pageRoot.ActualWidth/(PreferredImageWidth + ItemMargin));

                // Calculating rest and distribute among items
                var rest = (int) (pageRoot.ActualWidth%(PreferredImageWidth + ItemMargin));
                var additionalWidthPerItem = rest/itemsPerRow;

                ImageWidth = PreferredImageWidth + additionalWidthPerItem;
                ImageMargin = new Thickness(0, 0, ItemMargin, ItemMargin);
            }
        }
    }
}