XAML Behaviors for Avalonia UI

The Xaml.Behaviors.Interactions.Events package provides strongly-typed Behaviors and Triggers for Avalonia events. It allows you to handle input events (Pointer, Keyboard, Focus, Gestures, and Drag & Drop) directly in XAML.

Key capabilities include:

• Strongly Typed Wrappers: Uses dedicated classes (e.g., PointerPressedEventTrigger) instead of string-based event names.
• Routing Strategies: Supports the RoutingStrategies property to control whether an event is handled during the Tunnel, Bubble, or Direct phase.
• Base Classes: Provides abstract *EventBehavior classes to simplify creating custom reusable logic without manual event subscription boilerplate.

The Avalonia.Xaml.Interactions.Custom package provides specialized behaviors designed to work with SelectingItemsControl in Avalonia. These behaviors allow you to extend the functionality of controls like ListBox, ComboBox, or DataGrid by reacting to selection changes or implementing search/filtering logic.

Available behaviors include:

• SelectingItemsControlEventsBehavior: An abstract base class used to implement custom logic that responds to the SelectingItemsControl.SelectionChanged event.
• SelectingItemsControlSearchBehavior: A behavior that enables filtering the items within a SelectingItemsControl based on text input from a search box.

The package provides several specialized behaviors for different UI interaction scenarios:

• CanvasDragBehavior: Enables dragging child controls specifically within a Canvas container.
• MouseDragElementBehavior: Enables dragging a control by applying a TranslateTransform to it.
• ListReorderDragBehavior: Enables reordering items within an ItemsControl using drag-and-drop functionality.
• GridDragBehavior: Enables dragging child controls within a Grid, specifically for swapping rows or columns.

The Animations sample application provides practical examples of the following feature families:

• Key-frames: Using the key-frame factory, builder, and both synchronous and asynchronous runners.
• Fluid Movement: Demonstrating movement with automatic transform preparation.
• Animation Primitives: Implementation of fade, sliding, scale, and rotation.
• Animation Catalogs: Usage of attention, entrance, exit, Framer Motion, and special catalogs.
• UI Feedback: Selection indicator animations.
• Composition Effects: Orbit, tilt, and parallax effects.
• Collection Operations: Transition collection mutation and observation operations.

The Validation category provides a set of specialized behaviors and rules for validating UI controls in Avalonia.

Validation Behaviors

Behaviors are attached to specific control types to trigger validation logic based on user interaction:

• ComboBoxValidationBehavior
• DatePickerValidationBehavior
• NumericUpDownValidationBehavior
• PropertyValidationBehavior
• SliderValidationBehavior
• TextBoxValidationBehavior

Validation Rules

Rules define the specific logic used to determine if a value is valid. These are typically implemented via the IValidationRule interface:

• IValidationRule (Base interface)
• MaxValueValidationRule
• MinLengthValidationRule
• MinValueValidationRule
• NotNullValidationRule
• RangeValidationRule
• RegexValidationRule
• RequiredDateValidationRule
• RequiredDecimalValidationRule
• RequiredTextValidationRule

The Avalonia.Xaml.Interactions.Custom package provides a set of behaviors designed to trigger the visibility of a control in response to specific user interaction events.

Available behaviors include:

• ShowOnDoubleTappedBehavior: Shows a control when a double-tap event occurs.
• ShowOnKeyDownBehavior: Shows a control when a key-down event occurs.
• ShowOnTappedBehavior: Shows a control when a tap event occurs.

All these behaviors inherit from ShowBehaviorBase, which serves as the foundation for control visibility logic triggered by events.

The Gestures category provides a variety of interaction triggers that can be used to respond to user input patterns in Avalonia. These triggers allow you to attach specific actions to complex input events like pinching, scrolling, or touchpad-specific gestures.

Available triggers include:

• Tapping & Clicking: TappedGestureTrigger, DoubleTappedGestureTrigger, RightTappedGestureTrigger.
• Holding: HoldingGestureTrigger.
• Pinch & Zoom: PinchGestureTrigger, PinchEndedGestureTrigger.
• Scrolling: ScrollGestureGestureTrigger, ScrollGestureEndedGestureTrigger, ScrollGestureInertiaStartingGestureTrigger.
• Pulling: PullGestureGestureTrigger, PullGestureEndedGestureTrigger.
• Touchpad Specific: PointerTouchPadGestureSwipeGestureTrigger, PointerTouchPadGestureRotateGestureTrigger, PointerTouchPadGestureMagnifyGestureTrigger.