Question

我从windows phone工具包中实现了HubTile控件的以下实现，除了从选定的磁贴实现tap事件外，一切正常。我不确定如何将特定磁贴的点击链接到后面的代码中的Tap事件处理程序（这应该只是导航到我的项目中的新页面）。我到目前为止的内容如下：

MainPage.xaml中

<ListBox Grid.Row="0" x:Name="tileList" toolkit:TiltEffect.IsTiltEnabled="True">
                <ListBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <toolkit:WrapPanel Orientation="Horizontal" />
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <toolkit:HubTile Title="{Binding Title}" Margin="3"
                                         Notification="{Binding Notification}"
                                         DisplayNotification="{Binding DisplayNotification}"
                                         Message="{Binding Message}"
                                         GroupTag="{Binding GroupTag}"
                                         Source="{Binding ImageUri}"
                                         Tap="hubTile_Tap">
                        </toolkit:HubTile>

                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>

TileItem.cs

public class TileItem
{
    public string ImageUri
    {
        get;
        set;
    }

    public string Title
    {
        get;
        set;
    }

    public string Notification
    {
        get;
        set;
    }

    public bool DisplayNotification
    {
        get
        {
            return !string.IsNullOrEmpty(this.Notification);
        }
    }

    public string Message
    {
        get;
        set;
    }

    public string GroupTag
    {
        get;
        set;
    }

    //not sure how to implement this?
    public string Tap
    {
        get;
        set;
    }
}

MainPage.xaml.cs中

    #region Ctr

    public MainPage()
    {
        InitializeComponent();

        CreateHubTiles();
    }

    #endregion

    private void CreateHubTiles()
    {
        List<TileItem> tileItems = new List<TileItem>() 
        {
            //there will be at least 2 distinct tiles linking to seperate pages
            new TileItem() { ImageUri = "/Images/shareStatusImage.jpg", Title = "status", /*Notification = "last shared link uri",*/ Message = "last shared status message", GroupTag = "TileGroup", Tap = "shareStatus_Tap" },
            new TileItem() { ImageUri = "/Images/shareLinkImage.jpg", Title = "link", /*Notification = "last shared status message",*/ Message = "last shared link uri", GroupTag = "TileGroup", Tap = "shareLink_Tap" }
        };

        this.tileList.ItemsSource = tileItems;
    }

    #region Navigation

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

        HubTileService.UnfreezeGroup("TileGroup");
    }

    protected override void OnNavigatedFrom(NavigationEventArgs e)
    {
        base.OnNavigatedFrom(e);

        HubTileService.FreezeGroup("TileGroup");
    }

    #endregion

    #region Event Handlers

    private void hubTile_Tap(object sender, System.Windows.Input.GestureEventArgs e)
    {
        TileItem tap = sender as TileItem;
        string _tap = tap.Tap.ToString();  //NullReferenceException occurs here

        switch(_tap)
        {
            case "shareStatus_Tap":
                this.NavigationService.Navigate(new Uri("/Views/ShareStatusPage.xaml", UriKind.Relative));
                break;
            case "shareLink_Tap":
                this.NavigationService.Navigate(new Uri("/Views/ShareLinkPage.xaml", UriKind.Relative));
                break;
        }
    }
    #endregion

在模拟器中MainPage加载活动的hubtiles工作，但tap事件导致NullReferenceException，而在我的实际设备上，应用程序根本没有加载？

Answer 1

将您的断点放在hubTile_Tap中，看看sender是什么。我猜这将是HubTile，而不是TileItem。在这种情况下，TileItem可能是HubTile.DataContext。

Answer 2

我的写作和@JohnGardner一样，所以我会跳过它。请小心发件人。实际上在某些情况下它可能是任何事情。如果遇到这种情况，请尝试检查System.Windows.Input.GestureEventArgs e及其Source和OriginalSource - 它们可能不一定是HubTile，并且没有必要的有趣的DataContext，但它们几乎可以保证它们是Visual或UIElement，您可以轻松地向上追踪他们的VisualParents，并且一个关闭的可视父级将是您的DataContext = TileItem的HubTile。这是最糟糕的情况。首先，尝试约翰所说的，你有95％它会起作用：）

如何将tap事件添加到多个HubTiles

2 个答案: