How to activate an app (XAML)

Learn how to handle activation for your app. The example in this topic overrides the OnLaunched method.

Roadmap: How does this topic relate to others? See:

• Roadmap for Windows Runtime apps using C# or Visual Basic
• Roadmap for Windows Runtime apps using C++

Instructions

Step 1: Override the launch handler

When an app is activated, for any reason, the system sends the Activated event. For a list of activation types, see the ActivationKind enumeration.

The Windows.UI.Xaml.Application class defines methods you can override to handle the various activation types. Several of the activation types have a specific method that you can override. For the other activation types, override the OnActivated method.

Define the class for your application.

<Application xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml" 
             x:Class="AppName.App" >

Override the OnLaunched method. This method is called whenever the user launches the app. The LaunchActivatedEventArgs parameter contains the previous state of your app and the activation arguments.

Note  For Windows Phone Store apps, this method is called each time the user launches the app from Start tile or app list, even when the app is currently suspended in memory. On Windows, launching a suspended app from Start tile or app list doesn’t call this method.

using System;
using Windows.ApplicationModel.Activation;
using Windows.UI.Xaml;

namespace AppName
{
   public partial class App
   {
      async protected override void OnLaunched(LaunchActivatedEventArgs args)
      {
         EnsurePageCreatedAndActivate();
      }

      // Creates the MainPage if it isn't already created.  Also activates
      // the window so it takes foreground and input focus.
      private MainPage EnsurePageCreatedAndActivate()
      {
         if (Window.Current.Content == null)
         {
             Window.Current.Content = new MainPage();
         }

         Window.Current.Activate();
         return Window.Current.Content as MainPage;
      }
   }
}

Class App

   Protected Overrides Sub OnLaunched(args As LaunchActivatedEventArgs)
      Window.Current.Content = New MainPage()
      Window.Current.Activate()
   End Sub

End Class

using namespace Windows::ApplicationModel::Activation;
using namespace Windows::Foundation;
using namespace Windows::UI::Xaml;
using namespace AppName;

void App::OnLaunched(LaunchActivatedEventArgs^ args)
{
   EnsurePageCreatedAndActivate();
}

// Creates the MainPage if it isn't already created.  Also activates
// the window so it takes foreground and input focus.
void App::EnsurePageCreatedAndActivate()
{
    if (_mainPage == nullptr)
    {
        // Save the MainPage for use if we get activated later
        _mainPage = ref new MainPage();
    }
    Window::Current->Content = _mainPage;
    Window::Current->Activate();
}

Step 2: Restore application data if app was suspended then terminated

When the user switches to your terminated app, the system sends the Activated event, with Kind set to Launch and PreviousExecutionState set to Terminated or ClosedByUser. The app should load its saved application data and refresh its displayed content.

async protected override void OnLaunched(LaunchActivatedEventArgs args)
{
   if (args.PreviousExecutionState == ApplicationExecutionState.Terminated ||
       args.PreviousExecutionState == ApplicationExecutionState.ClosedByUser)
   {
      // TODO: Populate the UI with the previously saved application data
   }
   else
   {
      // TODO: Populate the UI with defaults
   }

   EnsurePageCreatedAndActivate();
}

Protected Overrides Sub OnLaunched(args As Windows.ApplicationModel.Activation.LaunchActivatedEventArgs)
   Dim restoreState As Boolean = False

   Select Case args.PreviousExecutionState
      Case ApplicationExecutionState.Terminated
         ' TODO: Populate the UI with the previously saved application data
         restoreState = True
      Case ApplicationExecutionState.ClosedByUser
         ' TODO: Populate the UI with the previously saved application data
         restoreState = True
      Case Else
         ' TODO: Populate the UI with defaults
   End Select

   Window.Current.Content = New MainPage(restoreState)
   Window.Current.Activate()
End Sub

void App::OnLaunched(Windows::ApplicationModel::Activation::LaunchActivatedEventArgs^ args)
{
   if (args->PreviousExecutionState == ApplicationExecutionState::Terminated ||
       args->PreviousExecutionState == ApplicationExecutionState::ClosedByUser)
   {
      // TODO: Populate the UI with the previously saved application data
   }
   else
   {
      // TODO: Populate the UI with defaults
   }

   EnsurePageCreatedAndActivate();
}

If the value of PreviousExecutionState is NotRunning, the app failed to save its application data successfully and the app should start over as if it were being initially launched.

Remarks

Note  

For Windows Phone Store apps, the Resuming event is always followed by OnLaunched, even when your app is currently suspended and the user re-launches your app from a primary tile or app list. Apps can skip initialization if there is already content set on the current window. You can check the LaunchActivatedEventArgs.TileId property to determine if the app was launched from a primary or a secondary tile and, based on that information, decide whether you should present a fresh or resume app experience.

Related topics

Tasks

How to suspend an app

How to resume an app

Conceptual

Application lifecycle

Guidelines

Guidelines for app suspend and resume

Reference

Windows.ApplicationModel.Activation

Windows.UI.Xaml.Application