Book Image

Windows Application Development Cookbook

By : Marcin Jamro
Book Image

Windows Application Development Cookbook

By: Marcin Jamro

Overview of this book

Need to ensure you can always create the best Windows apps regardless of platform? What you need are solutions to the biggest issues you can face, so you can always ensure you’re making the right choices and creating the best apps you can. The book starts with recipes that will help you set up the integrated development environment before you go ahead and design the user interface. You will learn how to use the MVVM design pattern together with data binding, as well as how to work with data in different file formats. Moving on, you will explore techniques to add animations and graphics to your application, and enable your solution to work with multimedia content. You will also see how to use sensors, such as an accelerometer and a compass, as well as obtain the current GPS location. You will make your application ready to work with Internet-based scenarios, such as composing e-mails or downloading files, before finally testing the project and submitting it to the Windows Store. By the end of the book, you will have a market-ready application compatible across different Windows devices, including smartphones, tablets, and desktops.
Table of Contents (17 chapters)
Windows Application Development Cookbook
About the Author
About the Reviewer

Handling the back button

The UWP applications can be run on various devices that differ, for example, by availability of the back button. As you can see, such a button exists in the case of smartphones, but it is not available for tablets and desktops. Fortunately, it is possible to use the SystemNavigationManager class to handle pressing the back button on a smartphone to navigate to the previous page in the application. What is more, the mechanism allows you to present the additional back button, at the top of the window, in case of a tablet or desktop-based version. You will learn how to do it in the current recipe.

Getting ready

To complete this recipe, you need the project with two pages, represented by the MainPage and AboutPage classes. Let's imagine that the first page operates as the main menu of the application with a set of menu items. After clicking on the first of them, the user should be navigated to the page with information about the company.

How to do it...

To handle the back button on a smartphone, as well as present an additional back button on tablets and desktops, you need to perform the following steps:

  1. Specify the visibility of the additional back button (on devices without such a button), as well as handle an event of using it. To do so, modify the code of the OnLaunched method in the App.xaml.cs file, as shown as follows:

            protected override void OnLaunched( 
                LaunchActivatedEventArgs e) 
            { (...) 
                if (rootFrame == null) 
                    rootFrame = new Frame(); (...) 
                    Window.Current.Content = rootFrame; 
                    rootFrame.Navigated += (s, ev) => 
                           .AppViewBackButtonVisibility = 
                                ((Frame)s).CanGoBack ? 
                                AppViewBackButtonVisibility.Visible : 
                        .BackRequested += OnBackRequested; 
                } (...) 

  2. Go back to the previous page when the back button is used, by adding the OnBackRequested method in the App.xaml.cs file, as shown as follows:

            private void OnBackRequested(object sender,  
                BackRequestedEventArgs e) 
                Frame rootFrame = (Frame)Window.Current.Content; 
                if (rootFrame.CanGoBack) 
                    e.Handled = true; 

How it works...

By adding the necessary code directly in the App.xaml.cs file, you do not need to specify the same operations in all .xaml.cs files representing pages. The required lines of code are not very complicated and are explained in the following part of this recipe.

First of all, you handle the Navigated event on an instance representing the frame (the roomFrame variable of the Frame type). When a user navigates to some page, the visibility of the back button is specified. Of course, it should be visible only when it is possible to go back from the current page, as specified in the following part of code:

        .AppViewBackButtonVisibility = ((Frame)s).CanGoBack ? 
            AppViewBackButtonVisibility.Visible : 

Then, you handle an event of the back button being clicked, namely BackRequested. Of course, it supports a scenario of both pressing the hardware-based version and clicking on the additional back button added in the top-left corner of the window, as presented in the following screenshot of mobile and desktop-based versions:

When a user clicks on the back button, the OnBackRequested method is called. Within it, you check whether it is possible to go back from the current page. In such a case, you indicate that the event is handled and call the GoBack method. The operation of such a method is explained in detail in the Navigating between pages recipe.

See also

  • The Navigating between pages recipe

  • The Passing data between pages recipe

  • The Changing a default page recipe

  • The Modifying the back stack recipe