Show multiple views with ApplicationView

Help your users be more productive by letting them view independent parts of your app in separate windows. When you create multiple windows for an app, each window behaves independently. The taskbar shows each window separately. Users can move, resize, show, and hide app windows independently and can switch between app windows as if they were separate apps. Each window operates in its own thread.

Important APIs: ApplicationViewSwitcher, CreateNewView

What is a view?

An app view is the 1:1 pairing of a thread and a window that the app uses to display content. It's represented by a Windows.ApplicationModel.Core.CoreApplicationView object.

Views are managed by the CoreApplication object. You call CoreApplication.CreateNewView to create a CoreApplicationView object. The CoreApplicationView brings together a CoreWindow and a CoreDispatcher (stored in the CoreWindow and Dispatcher properties). You can think of the CoreApplicationView as the object that the Windows Runtime uses to interact with the core Windows system.

You typically don’t work directly with the CoreApplicationView. Instead, the Windows Runtime provides the ApplicationView class in the Windows.UI.ViewManagement namespace. This class provides properties, methods, and events that you use when your app interacts with the windowing system. To work with an ApplicationView, call the static ApplicationView.GetForCurrentView method, which gets an ApplicationView instance tied to the current CoreApplicationView’s thread.

Likewise, the XAML framework wraps the CoreWindow object in a Windows.UI.XAML.Window object. In a XAML app, you typically interact with the Window object rather than working directly with the CoreWindow.

Show a new view

While each app layout is unique, we recommend including a "new window" button in a predictable location, such as the top right corner of the content that can be opened in a new window. Also consider including a context menu option to "Open in a new window".

Let's look at the steps to create a new view. Here, the new view is launched in response to a button click.

private async void Button_Click(object sender, RoutedEventArgs e)
{
    CoreApplicationView newView = CoreApplication.CreateNewView();
    int newViewId = 0;
    await newView.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        Frame frame = new Frame();
        frame.Navigate(typeof(SecondaryPage), null);   
        Window.Current.Content = frame;
        // You have to activate the window in order to show it later.
        Window.Current.Activate();

        newViewId = ApplicationView.GetForCurrentView().Id;
    });
    bool viewShown = await ApplicationViewSwitcher.TryShowAsStandaloneAsync(newViewId);
}

To show a new view

1. Call CoreApplication.CreateNewView to create a new window and thread for the view content.

   CoreApplicationView newView = CoreApplication.CreateNewView();
   

2. Track the Id of the new view. You use this to show the view later.

   You might want to consider building some infrastructure into your app to help with tracking the views you create. See the ViewLifetimeControl class in the MultipleViews sample for an example.

   int newViewId = 0;
   

3. On the new thread, populate the window.

   You use the CoreDispatcher.RunAsync method to schedule work on the UI thread for the new view. You use a lambda expression to pass a function as an argument to the RunAsync method. The work you do in the lambda function happens on the new view's thread.

   In XAML, you typically add a Frame to the Window's Content property, then navigate the Frame to a XAML Page where you've defined your app content. For more info about frames and pages, see Peer-to-peer navigation between two pages.

   After the new Window is populated, you must call the Window's Activate method in order to show the Window later. This work happens on the new view's thread, so the new Window is activated.

   Finally, get the new view's Id that you use to show the view later. Again, this work is on the new view's thread, so ApplicationView.GetForCurrentView gets the Id of the new view.

   await newView.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
   {
       Frame frame = new Frame();
       frame.Navigate(typeof(SecondaryPage), null);   
       Window.Current.Content = frame;
       // You have to activate the window in order to show it later.
       Window.Current.Activate();
   
       newViewId = ApplicationView.GetForCurrentView().Id;
   });
   

4. Show the new view by calling ApplicationViewSwitcher.TryShowAsStandaloneAsync.

   After you create a new view, you can show it in a new window by calling the ApplicationViewSwitcher.TryShowAsStandaloneAsync method. The viewId parameter for this method is an integer that uniquely identifies each of the views in your app. You retrieve the view Id by using either the ApplicationView.Id property or the ApplicationView.GetApplicationViewIdForWindow method.

   bool viewShown = await ApplicationViewSwitcher.TryShowAsStandaloneAsync(newViewId);
   

The main view

The first view that’s created when your app starts is called the main view. This view is stored in the CoreApplication.MainView property, and its IsMain property is true. You don’t create this view; it’s created by the app. The main view's thread serves as the manager for the app, and all app activation events are delivered on this thread.

If secondary views are open, the main view’s window can be hidden – for example, by clicking the close (x) button in the window title bar - but its thread remains active. Calling Close on the main view’s Window causes an InvalidOperationException to occur. (Use Application.Exit to close your app.) If the main view’s thread is terminated, the app closes.

Secondary views

Other views, including all views that you create by calling CreateNewView in your app code, are secondary views. Both the main view and secondary views are stored in the CoreApplication.Views collection. Typically, you create secondary views in response to a user action. In some instances, the system creates secondary views for your app.

Switch from one view to another

Consider providing a way for the user to navigate from a secondary window back to its parent window. To do this, use the ApplicationViewSwitcher.SwitchAsync method. You call this method from the thread of the window you're switching from and pass the view ID of the window you're switching to.

await ApplicationViewSwitcher.SwitchAsync(viewIdToShow);

When you use SwitchAsync, you can choose if you want to close the initial window and remove it from the taskbar by specifying the value of ApplicationViewSwitchingOptions.

Related topics

• Show multiple views
• Show multiple views with AppWindow
• ApplicationViewSwitcher
• CreateNewView