Question

我想要导航到我的Windows Phone 8.1应用程序中的另一个页面。如果有一个按钮，只需点击它并使用Frame.Navigate(typeof(MainPage));中的event handler即可轻松完成此操作。但在我的情况下我想根据整数值自动导航到第二页。如果它变为零，页面会自动转到第二页。在我的情况下，我没有button所以event handler这样做这个。我怎么能这样做？

Answer 1

为您的视图模型实现INotifyPropertyChanged接口。这是一个粗略的实现，理想情况下，您将使用mvvm框架并根据需要向您的视图发送消息。

查看模型

public class GameStateViewModel : INotifyPropertyChanged
{
    private int currentScore = 10;

    /// <summary>
    /// The timer here added to simulate whatever is supposed to be changing your value. 
    /// </summary>
    public GameStateViewModel()
    {
        var timer = new DispatcherTimer
        {
            Interval = TimeSpan.FromSeconds(2)
        };

        timer.Tick += (sender, args) =>
        {
            if (this.CurrentScore > 0)
            {
                this.CurrentScore--;
            }
            else
            {
                timer.Stop();
            }
        };

        timer.Start();
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public int CurrentScore
    {
        get { return currentScore; }
        set
        {
            currentScore = value;
            NotifyPropertyChanged("CurrentScore");
        }
    }

    public void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

背后的代码

 public partial class MainPage : PhoneApplicationPage
{
    // Constructor
    public MainPage()
    {
        InitializeComponent();

        var viewModel = new GameStateViewModel();

        viewModel.PropertyChanged += (sender, args) =>
        {
            if (viewModel.CurrentScore <= 0)
            {
                this.NavigationService.Navigate(new Uri("/Page2.xaml", UriKind.Relative));
            }
        };

        this.DataContext = viewModel;

    }
}

的Xaml

 <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
        <TextBlock Text="{Binding CurrentScore}" FontSize="{StaticResource PhoneFontSizeExtraLarge}" />
    </Grid>

在C＃和XAML中导航

1 个答案: