Backbutton handling with #winprt and Windows Phone 8.1 #wpdev

Back with WP8 and Silverlight API, handling hardware back button was easy peasy. By default, PhoneApplicationPage exposed an eventhandler called BackKeyPress. Developers could chose to subscribe to this event handler and handle the back button.

<phone:PhoneApplicationPage shell:SystemTray.IsVisible="True" BackKeyPress="PhoneApplicationPage_BackKeyPress">
...
...
...
</phone:PhoneApplicationPage>

private void PhoneApplicationPage_BackKeyPress(object sender, System.ComponentModel.CancelEventArgs e)
{
    if (this.DrawingCanvas.Visibility == System.Windows.Visibility.Visible)
    {
        this.DrawingCanvas.Visibility = this.ColorSlider.Visibility = System.Windows.Visibility.Collapsed;
        this.piWords.IsLocked = false;
        e.Cancel = true;
    }
}

As you can see, in the back key press, I check to see if certain view is being shown and if so, I hide it that rather than navigating page backstack.

That was Silverlight / WP API.. how would we do that in WP8.1 / WinPRT API ?
Windows.Phone.UI.Input namespace contains a class called HardwareButtons. just remember this is WP8.1 WinPRT API only – not supported on Windows store apps. Sadly no XAML wiring up.. lets go to codebehind and subscribe to it


public MainPage()
{
    this.InitializeComponent();

    this.NavigationCacheMode = NavigationCacheMode.Required;

    HardwareButtons.BackPressed += HardwareButtons_BackPressed;
}

void HardwareButtons_BackPressed(object sender, BackPressedEventArgs e)
{
    if (some_condition)
    {
        e.Handled = true;
    }
}

That’s about it.. thank goodness I still have Dev preview documentation lying around 🙂