.NET MAUI: Bug – GestureRecognizers are not working on some views

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In the world of software development, bugs can occasionally arise, causing unexpected behavior in our applications. In this blog post, we will explore a bug affecting TapGestureRecognizers in .NET MAUI apps, specifically on certain Views like frames. We’ll discuss the symptoms of this bug and provide a practical workaround to ensure that TapGestureRecognizers properly fire events or execute commands.

Symptoms

The bug we are addressing is related to TapGestureRecognizers not functioning as expected on specific Views, such as frames, in .NET MAUI apps. This issue prevents TapGestureRecognizers from triggering events or executing commands, leading to a loss of interactivity for the affected Views.

Workaround

To overcome this bug, we can utilize a simple workaround that involves creating a transparent BoxView on top of the desired interaction area. By setting the InputTransparent property of the BoxView to false, we allow it to capture touch events, effectively acting as an overlay for the affected View. We can then assign the TapGestureRecognizer to the transparent BoxView to regain the desired interactivity.

First, identify the View that is experiencing the issue with TapGestureRecognizers. In this example, let’s assume we have a Frame control that should respond to tap events but is currently affected by the bug. Add a Transparent BoxView Within the same container as the affected View, add a BoxView control. Set its BackgroundColor property to Transparent to ensure it remains invisible to the user. Assign TapGestureRecognizer to the Transparent BoxView Inside the GestureRecognizers collection of the transparent BoxView, assign the TapGestureRecognizer with the desired event handling or command execution logic. You can bind the command property to a command in your view model or handle the event in code-behind. Position the transparent BoxView over the affected View, ensuring that it covers the same area where the TapGestureRecognizer should have been applied. By making the BoxView transparent and setting InputTransparent to false, it allows touch events to pass through, reaching the TapGestureRecognizer.

<BoxView BackgroundColor="Transparent" InputTransparent="False">
    <BoxView.GestureRecognizers>
        <TapGestureRecognizer Command="{Binding YourCommand}" />
    </BoxView.GestureRecognizers>
</BoxView>

Note: It’s important to keep in mind that this workaround is intended as a temporary solution until the bug is officially addressed and fixed by the .NET MAUI team. Stay up to date with the latest releases and bug fixes to ensure that you can eventually transition to the official resolution. Please remember to regularly check the official .NET MAUI documentation, release notes, and bug tracking system for any updates regarding this bug and its resolution.

https://github.com/dotnet/maui/issues/8895#issuecomment-1301620712

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.NET MAUI: Implementing Light and Dark Modes

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In modern application development, providing users with the ability to switch between light and dark modes has become an essential feature. This functionality not only enhances user experience but also accommodates personal preferences and improves accessibility. In this blog post, we will explore how to implement light and dark modes in .NET MAUI apps using the UserAppTheme property in the App.xaml.cs file.

Understanding the App.xaml.cs File

The App.xaml.cs file in a .NET MAUI application is responsible for defining the application’s startup and initialization logic. It acts as the entry point for the application and provides a central location to handle events and configure application-wide settings.

Setting the UserAppTheme Property

To enable light and dark modes in your .NET MAUI app, you need to access the UserAppTheme property available in the Application.Current object. This property allows you to specify the desired theme for your application.

If your application does not allow the users to change the light/dark modes, but you want to force the app to be in a specified state, you can use the App.xaml.cs constructor, and you can set the UserAppTheme property to either AppTheme.Light or AppTheme.Dark, depending on a predefined default.

Here’s an example of how to set the AppTheme to Light mode:

Application.Current.UserAppTheme = AppTheme.Light;

Similarly, you can set the AppTheme to Dark mode:

Application.Current.UserAppTheme = AppTheme.Dark;
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.NET MAUI: Save any type of object in Preferences

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.NET MAUI currently have limitations of the supported types in preferences. They can only store simple data types such as strings, integers, and booleans, and do not support more complex data types such as lists or objects. This can make it difficult to store and retrieve more complex data structures.

How to store arrays and lists, or complex classes in Preferences?

The answer is currently to serialize it. Since Preferences is supporting string saving option, you can serialize your arrays and custom classes, and store the string value.

But be aware to store large amounts of data in Preferences as a string. Consider choosing SQLite to store data when there are more than 50-100 items in an array, or your class is more complex than having 25 properties. As Microsoft marks this as a limitation: Performance may be impacted if you store large amounts of text, as the API was designed to store small amounts of text.

But there are cases when it makes sense to store other types

There are cases when it is easier to store a whole complex object on disk than to store all its properties one by one by calling preferences Set. In this case you may find useful the banditoth.MAUI.PreferencesExtension.

Usage

This package is extending the basic functions of the built in MAUI Essentials IPreferences by letting the developers to save any type of object. This is done by using JSON serialization, and saving the raw jsons as strings with the default IPreferences implementation. Since JSON arrays can be serialized back to any collection type, you can use different types when Setting the value and when Getting it back.

There are several ways to access this extension.

Dependency Injection

    private readonly IPreferences preferences;

    public MainPage(IPreferences preferences)
    {
        InitializeComponent();
        this.preferences = preferences;
    }

    private void Foo()
    {
        List<string> taleItems = new List<string>()
        {
            "The quick brown fox",
            "Jumps over the lazy dog"
        };

        preferences.SetObject<List<string>>("Tale", taleItems);

        string[] taleItemsFromPreferences = preferences.GetObject<string[]>("Tale", null);
    }

Access through Preferences

If you are used to access the preferences trough the static class, you can use this tool by accessing the Default property on the Preferences class. You can call the SetObject or GetObject extension method on it.

            // Setting the value
            Preferences.Default.SetObject<IDeviceInfo>("Device_Information", DeviceInfo.Current);
            // Getting the value
            Preferences.Default.GetObject<IDeviceInfo>("Device_Information", null);

Package’s own static reference

You can also access the SetObject or GetObject method on PreferencesExtension static class.

            // Setting the value
            PreferencesExtension.SetObject<DisplayOrientation>("Last_Display_Orientation", orientation);
            // Getting the value
            PreferencesExtension.GetObject<DisplayOrientation>("Last_Display_Orientation", DisplayOrientation.Landscape);
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.NET MAUI: Get unique device and installation ids for your app

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Why unique device and installations identifiers are important?

First, let’s define what we mean by a unique device and installation identifiers. Essentially, these are codes that are assigned to individual devices and installations of an app. They allow developers to track usage on a specific device and identify individual installations of the app. This is important because it allows us to understand how users are interacting with our app and identify patterns in usage. For example, if we notice that a particular device is experiencing a high number of crashes, we can use the device ids to track down the specific device and troubleshoot the issue.

Another important use case for unique device and installation identifiers is providing targeted and personalized content or experiences for users. For example, we can use this information to show users personalized advertisements or to offer them special deals or promotions based on their usage patterns.

In addition to these benefits, device and install ids also play an important role in security and fraud prevention. By tracking the usage of our app on specific devices, we can identify and prevent unauthorized access to the app or service. This can help to protect user data and prevent fraud and other malicious activities.

How to get unique identifiers in .NET MAUI?

On Android, you can get a unique device id from the os with accessing Secure.AndroidId.
On iOS, UIDevice.CurrentDevice.IdentifierForVendor is the solution. It requires platform specific knowledge to access the provider APIs. I’ve extended my banditoth.MAUI.Packages library, so you do not need to worry about having this knowledge, just use the banditoth.MAUI.DeviceId NuGet package.

Once you have installed banditoth.MAUI.DeviceId, you need to initalize  the plugin within your MauiProgram.cs‘s CreateMauiApp method. Use the .ConfigureDeviceIdProvider extension method with the using banditoth.MAUI.DeviceId;

    public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();
        builder
            .UseMauiApp<App>()
            .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
            })
            .ConfigureDeviceIdProvider();
#if DEBUG
        builder.Logging.AddDebug();
#endif

        return builder.Build();
    }

Use the code with by resolving an instance of IDeviceIdProvider.

The GetDeviceId method returns an unique device identifier. On Android it serves the data from AndroidId, on iOS and MacCatalyst it uses the IdentifierForVendor. Windows returns the GetSystemIdForPublisher().Idas a string.

The GetInstallationId method generates an unique identifier for the application, which will be stored until the application is being reinstalled, or the application’s data being erased.

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.NET Error: “The current NET SDK does not support targeting NET 7.0.”

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The current NET SDK does not support targeting NET 7.0. Either target . NET 6.0 or lower, or use a version of the NET SDK that supports .NET 7.0.

This error message is indicating that the version of the .NET SDK that you are currently using does not support targeting .NET 7.0. In order to resolve this error, you have three options:

  • Update your Visual Studio instance to the latest available.
  • Target .NET 6.0 or lower in your application by modifying the target framework in your project file (e.g. .csproj) to a version lower than 7.0, and then rebuild your application.
  • Use a version of the .NET SDK that supports .NET 7.0. You can check the version of the SDK you are currently using by running dotnet --version in a command prompt or terminal, and then update it to the latest version that supports .NET 7.0.
    • You can check the SDK version by running dotnet –list-sdks and you can update your SDK version by running dotnet update sdk
    • Once you have updated your SDK version, you should be able to build your application targeting .NET 7.0 without encountering this error.
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