Xamarin Cheatsheet

Xamarin - Cross-Platform Mobile Apps with .NET

Xamarin ist eine Open-Source-Plattform zum Erstellen moderner und leistungsfähiger Anwendungen für iOS, Android und Windows mit .NET. Xamarin ist eine Abstraktionsschicht, die die Kommunikation von gemeinsam genutztem Code mit zugrunde liegender Plattform-Code verwaltet.

📋 Copy All Commands 📄 Generate PDF(This section was empty in the original text, so no translation is needed) ```bash # Install Visual Studio (Windows) or Visual Studio for Mac (macOS) # Make sure to include the "Mobile development with .NET" workload

For iOS development on Windows, you need a Mac with Xcode and Visual Studio for Mac installed

```bash
# Open Visual Studio Installer
# Check if "Mobile development with .NET" is installed

# Check for Android SDK and NDK
# Visual Studio > Tools > Options > Xamarin > Android Settings

# Check for Xcode and Apple SDKs (macOS)
# Visual Studio for Mac > Preferences > Projects > SDK Locations > Apple
```(This section was empty in the original text, so no translation is needed)
```bash
# In Visual Studio
# File > New > Project
# Select "Mobile App (Xamarin.Forms)"
# Choose a template (Blank, Tabbed, Shell)

# In Visual Studio for Mac
# File > New Solution
# Select "Multiplatform > App > Xamarin.Forms"
# Choose a template (Blank, Tabbed, Shell)
```(This section was empty in the original text, so no translation is needed)
```bash
# Select a startup project (Android or iOS)
# Choose a device or emulator
# Click the "Run" button or press F5
```(This section was empty in the original text, so no translation is needed)

MyApp/ ├── MyApp/ # .NET Standard library (shared code) │ ├── App.xaml │ ├── App.xaml.cs │ ├── MainPage.xaml │ ├── MainPage.xaml.cs │ ├── Models/ │ ├── Views/ │ ├── ViewModels/ │ └── Services/ ├── MyApp.Android/ # Android-specific project │ ├── MainActivity.cs │ ├── Resources/ │ └── Assets/ ├── MyApp.iOS/ # iOS-specific project │ ├── AppDelegate.cs │ ├── Main.cs │ └── Info.plist └── MyApp.sln # Solution file

```csharp
// ContentPage
public class MyContentPage : ContentPage
{
    public MyContentPage()
    {
        Content = new StackLayout
        {
            Children = { new Label { Text = "Welcome to Xamarin.Forms!" } }
        };
    }
}

// TabbedPage
public class MyTabbedPage : TabbedPage
{
    public MyTabbedPage()
    {
        Children.Add(new MyContentPage { Title = "Tab 1" });
        Children.Add(new MyContentPage { Title = "Tab 2" });
    }
}

// FlyoutPage (Master-Detail)
public class MyFlyoutPage : FlyoutPage
{
    public MyFlyoutPage()
    {
        Flyout = new ContentPage { Title = "Menu" };
        Detail = new NavigationPage(new MyContentPage());
    }
}
```(This section was empty in the original text, so no translation is needed)
```csharp
// StackLayout
new StackLayout
{
    Orientation = StackOrientation.Vertical,
    Spacing = 10,
    Children = { new Label(), new Button() }
};

// Grid
new Grid
{
    RowDefinitions = { new RowDefinition { Height = GridLength.Auto } },
    ColumnDefinitions = { new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) } },
    Children = { { new Label(), 0, 0 } }
};

// FlexLayout
new FlexLayout
{
    Direction = FlexDirection.Row,
    JustifyContent = FlexJustify.SpaceBetween,
    Children = { new Label(), new Button() }
};

// AbsoluteLayout
new AbsoluteLayout
{
    Children = { { new BoxView { Color = Colors.Blue }, new Rectangle(0, 0, 100, 100) } }
};

// RelativeLayout
new RelativeLayout
{
    Children = { { new BoxView(), Constraint.Constant(0) } }
};
```(This section was empty in the original text, so no translation is needed)
```csharp
// Label
new Label { Text = "Hello, Xamarin!", FontSize = 24 };

// Button
new Button { Text = "Click Me", Command = new Command(() => DisplayAlert("Title", "Message", "OK")) };

// Entry
new Entry { Placeholder = "Enter text" };

// Editor
new Editor { Placeholder = "Enter multi-line text" };

// SearchBar
new SearchBar { Placeholder = "Search..." };

// Slider
new Slider { Minimum = 0, Maximum = 100 };

// Stepper
new Stepper { Minimum = 0, Maximum = 10 };

// Switch
new Switch { IsToggled = true };

// DatePicker
new DatePicker();

// TimePicker
new TimePicker();

// ListView
new ListView
{
    ItemsSource = new[] { "Item 1", "Item 2" },
    ItemTemplate = new DataTemplate(() =>
    {
        var cell = new TextCell();
        cell.SetBinding(TextCell.TextProperty, ".");
        return cell;
    })
};

// CollectionView
new CollectionView
{
    ItemsSource = new[] { "Item 1", "Item 2" }
};
```(This section was empty in the original text, so no translation is needed)
```csharp
// MainActivity.cs
[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
public class MainActivity : AppCompatActivity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.activity_main);

        var button = FindViewById<Button>(Resource.Id.myButton);
        button.Click += (sender, e) =>
        {
            Toast.MakeText(this, "Button Clicked!", ToastLength.Short).Show();
        };
    }
}
```(This section was empty in the original text, so no translation is needed)
```csharp
// ViewController.cs
public partial class ViewController : UIViewController
{
    public ViewController(IntPtr handle) : base(handle) { }

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        var button = new UIButton(UIButtonType.System);
        button.Frame = new CGRect(20, 200, 280, 44);
        button.SetTitle("Click Me", UIControlState.Normal);
        button.TouchUpInside += (sender, e) =>
        {
            var alert = UIAlertController.Create("Title", "Message", UIAlertControllerStyle.Alert);
            alert.AddAction(UIAlertAction.Create("OK", UIAlertActionStyle.Default, null));
            PresentViewController(alert, true, null);
        };
        View.AddSubview(button);
    }
}
```(This section was empty in the original text, so no translation is needed)
```xml
<!-- MainPage.xaml -->
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MyApp.MainPage">
    <StackLayout>
        <Label Text="Welcome to Xamarin.Forms!"
               VerticalOptions="CenterAndExpand" 
               HorizontalOptions="CenterAndExpand" />
        <Button Text="Click Me" Clicked="OnButtonClicked" />
    </StackLayout>
</ContentPage>

// MainPage.xaml.cs
public partial class MainPage : ContentPage
{
    public MainPage()
    {
        InitializeComponent();
    }

    private void OnButtonClicked(object sender, EventArgs e)
    {
        DisplayAlert("Title", "Message", "OK");
    }
}
```(This section was empty in the original text, so no translation is needed)
```xml
<!-- ViewModel -->
public class MyViewModel : INotifyPropertyChanged
{
    private string _name;
    public string Name
    {
        get => _name;
        set
        {
            _name = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

<!-- XAML -->
<ContentPage.BindingContext>
    <local:MyViewModel />
</ContentPage.BindingContext>

<Entry Text="{Binding Name, Mode=TwoWay}" />
<Label Text="{Binding Name}" />
```(This section was empty in the original text, so no translation is needed)
```csharp
// Push a new page
await Navigation.PushAsync(new DetailsPage());

// Pop a page
await Navigation.PopAsync();

// Pop to root
await Navigation.PopToRootAsync();

// Pass data
await Navigation.PushAsync(new DetailsPage(item));

// Modal navigation
await Navigation.PushModalAsync(new ModalPage());
await Navigation.PopModalAsync();
```(This section was empty in the original text, so no translation is needed)
```csharp
// Define an interface in shared code
public interface ITextToSpeech
{
    void Speak(string text);
}

// Implement the interface in platform-specific projects
// Android
[assembly: Dependency(typeof(TextToSpeech_Android))]
namespace MyApp.Droid
{
    public class TextToSpeech_Android : ITextToSpeech { ... }
}

// iOS
[assembly: Dependency(typeof(TextToSpeech_iOS))]
namespace MyApp.iOS
{
    public class TextToSpeech_iOS : ITextToSpeech { ... }
}

// Use the service in shared code
DependencyService.Get<ITextToSpeech>().Speak("Hello, Xamarin!");
```(This section was empty in the original text, so no translation is needed)
```csharp
// Create a custom control in shared code
public class MyEntry : Entry { }

// Create a custom renderer in platform-specific projects
// Android
[assembly: ExportRenderer(typeof(MyEntry), typeof(MyEntryRenderer))]
namespace MyApp.Droid
{
    public class MyEntryRenderer : EntryRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
        {
            base.OnElementChanged(e);
            if (Control != null)
            {
                Control.SetBackgroundColor(Android.Graphics.Color.LightGreen);
            }
        }
    }
}

// iOS
[assembly: ExportRenderer(typeof(MyEntry), typeof(MyEntryRenderer))]
namespace MyApp.iOS
{
    public class MyEntryRenderer : EntryRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
        {
            base.OnElementChanged(e);
            if (Control != null)
            {
                Control.BackgroundColor = UIColor.FromRGB(204, 153, 255);
            }
        }
    }
}
```(This section was empty in the original text, so no translation is needed)
```csharp
// Create an effect in shared code
public class FocusEffect : RoutingEffect
{
    public FocusEffect() : base("MyApp.FocusEffect") { }
}

// Implement the effect in platform-specific projects
// Android
[assembly: ResolutionGroupName("MyApp")]
[assembly: ExportEffect(typeof(FocusEffect_Android), "FocusEffect")]
namespace MyApp.Droid
{
    public class FocusEffect_Android : PlatformEffect { ... }
}

// Use the effect in XAML
<Entry>
    <Entry.Effects>
        <local:FocusEffect />
    </Entry.Effects>
</Entry>
```(This section was empty in the original text, so no translation is needed)
```csharp
// Subscribe to a message
MessagingCenter.Subscribe<MainPage, string>(this, "Hi", (sender, arg) =>
{
    // Do something with the message
});

// Send a message
MessagingCenter.Send(this, "Hi", "John");

// Unsubscribe
MessagingCenter.Unsubscribe<MainPage, string>(this, "Hi");
```(This section was empty in the original text, so no translation is needed)```csharp
// Set a value
Preferences.Set("my_key", "my_value");

// Get a value
var value = Preferences.Get("my_key", "default_value");
```### Dateisystem
```csharp
// Get the local app data folder
var path = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
var filename = Path.Combine(path, "myfile.txt");

// Write to a file
File.WriteAllText(filename, "Hello, Xamarin!");

// Read from a file
var content = File.ReadAllText(filename);
```### SQLite
```csharp
// Install sqlite-net-pcl NuGet package

// Create a model
public class MyItem
{
    [PrimaryKey, AutoIncrement]
    public int ID { get; set; }
    public string Text { get; set; }
}

// Create a database connection
var db = new SQLiteAsyncConnection(dbPath);
await db.CreateTableAsync<MyItem>();

// Save an item
await db.InsertAsync(item);

// Get all items
var items = await db.Table<MyItem>().ToListAsync();
```## Netzwerk
```csharp
var client = new HttpClient();
var response = await client.GetAsync("https://api.example.com/items");
if (response.IsSuccessStatusCode)
{
    var content = await response.Content.ReadAsStringAsync();
    var items = JsonConvert.DeserializeObject<List<MyItem>>(content);
}
```### HttpClient
```csharp
// Install Refit NuGet package

// Define an interface
public interface IMyApi
{
    [Get("/items")]
    Task<List<MyItem>> GetItems();
}

// Use the interface
var api = RestService.For<IMyApi>("https://api.example.com");
var items = await api.GetItems();
```### Refit
```csharp
// Use a testing framework like NUnit or xUnit
[Test]
public void MyViewModel_MyCommand_ShouldDoSomething()
{
    // Arrange
    var viewModel = new MyViewModel();

    // Act
    viewModel.MyCommand.Execute(null);

    // Assert
    Assert.IsTrue(viewModel.MyProperty);
}
```## Testing
```csharp
// Use Xamarin.UITest
[Test]
public void AppLaunches()
{
    app.Screenshot("First screen.");
}

[Test]
public void TappingButton_ShouldNavigateToDetails()
{
    app.Tap(c => c.Button("MyButton"));
    app.WaitForElement(c => c.Marked("DetailsPage"));
    app.Screenshot("Details screen.");
}
```### Komponententests
```bash
# Build the app in Release mode
# Archive the app
# Distribute the archive (e.g., to Google Play)
```### UI-Tests
```bash
# Build the app in Release mode
# Archive the app
# Distribute the archive (e.g., to the App Store)
```## Bereitstellung