Class UIElement

Inheritance

Object

DispatcherObject

UIElement

Inherited Members

DispatcherObject.CheckAccess()

DispatcherObject.VerifyAccess()

DispatcherObject.Dispatcher

Object.ToString()

Object.Equals(Object)

Object.Equals(Object, Object)

Object.ReferenceEquals(Object, Object)

Object.GetHashCode()

Object.GetType()

Object.MemberwiseClone()

Namespace: nanoFramework.Presentation

Assembly: nanoFramework.Graphics.dll

Syntax

public abstract class UIElement : DispatcherObject

Constructors

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UIElement()

Declaration

protected UIElement()

Fields

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_horizontalAlignment

Declaration

protected HorizontalAlignment _horizontalAlignment

Field Value

Type	Description
HorizontalAlignment

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_verticalAlignment

Declaration

protected VerticalAlignment _verticalAlignment

Field Value

Type	Description
VerticalAlignment

Properties

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ActualHeight

Declaration

public int ActualHeight { get; }

Property Value

Type	Description
Int32

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ActualWidth

Declaration

public int ActualWidth { get; }

Property Value

Type	Description
Int32

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Height

Declaration

public int Height { get; set; }

Property Value

Type	Description
Int32

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HorizontalAlignment

Declaration

public HorizontalAlignment HorizontalAlignment { get; set; }

Property Value

Type	Description
HorizontalAlignment

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InstanceEventHandlersStore

Ensure the store has been created.

Declaration

protected Hashtable InstanceEventHandlersStore { get; }

Property Value

Type	Description
Hashtable

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IsArrangeValid

Determines if the RenderSize and position of child elements is valid.

Declaration

public bool IsArrangeValid { get; }

Property Value

Type	Description
Boolean

Remarks

A developer can force arrangement to be invalidated by calling InvalidateArrange. IsArrangeValid and IsMeasureValid are related, in that arrangement cannot be valid without measurement first being valid.

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IsEnabled

Fetches the value of the IsEnabled property

Declaration

public bool IsEnabled { get; set; }

Property Value

Type	Description
Boolean

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IsFocused

A property indicating if the button is focused on this element or not.

Declaration

public bool IsFocused { get; }

Property Value

Type	Description
Boolean

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IsMeasureValid

Determines if the DesiredSize is valid.

Declaration

public bool IsMeasureValid { get; }

Property Value

Type	Description
Boolean

Remarks

A developer can force arrangement to be invalidated by calling InvalidateMeasure. IsArrangeValid and IsMeasureValid are related, in that arrangement cannot be valid without measurement first being valid.

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IsVisible

A property indicating if this element is Visible or not.

Declaration

public bool IsVisible { get; }

Property Value

Type	Description
Boolean

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LogicalChildren

Declaration

protected UIElementCollection LogicalChildren { get; }

Property Value

Type	Description
UIElementCollection

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Parent

Declaration

public UIElement Parent { get; }

Property Value

Type	Description
UIElement

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RootUIElement

Declaration

public UIElement RootUIElement { get; }

Property Value

Type	Description
UIElement

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VerticalAlignment

Declaration

public VerticalAlignment VerticalAlignment { get; set; }

Property Value

Type	Description
VerticalAlignment

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Visibility

Visibility accessor

Declaration

public Visibility Visibility { get; set; }

Property Value

Type	Description
Visibility

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Width

Declaration

public int Width { get; set; }

Property Value

Type	Description
Int32

Methods

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AddHandler(RoutedEvent, RoutedEventHandler, Boolean)

Adds a routed event handler for the particular RoutedEvent

Declaration

public void AddHandler(RoutedEvent routedEvent, RoutedEventHandler handler, bool handledEventsToo)

Parameters

Type	Name	Description
RoutedEvent	routedEvent	RoutedEvent for which the handler is attached
RoutedEventHandler	handler	The handler that will be invoked on this object when the RoutedEvent is raised
Boolean	handledEventsToo	Flag indicating whether or not the listener wants to hear about events that have already been handled

Remarks

The handler added thus is also known as an instance handler

NOTE: It is not an error to add a handler twice (handler will simply be called twice)

Input parameters RoutedEvent and handler cannot be null

handledEventsToo input parameter when false means that listener does not care about already handled events. Hence the handler will not be invoked on the target if the RoutedEvent has already been Handled

handledEventsToo input parameter when true means that the listener wants to hear about all events even if they have already been handled. Hence the handler will be invoked irrespective of the event being Handled

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AddToEventRoute(EventRoute, RoutedEventArgs)

Add the event handlers for this element to the route.

Declaration

public void AddToEventRoute(EventRoute route, RoutedEventArgs args)

Parameters

Type	Name	Description
EventRoute	route
RoutedEventArgs	args

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Arrange(Int32, Int32, Int32, Int32)

Parents or system call this method to arrange the internals of children on a second pass of layout update.

Declaration

public void Arrange(int finalRectX, int finalRectY, int finalRectWidth, int finalRectHeight)

Parameters

Type	Name	Description
Int32	finalRectX	This is the final X location that parent or system wants this UIElement to assume.
Int32	finalRectY	This is the final Y location that parent or system wants this UIElement to assume.
Int32	finalRectWidth	This is the Width that parent or system wants this UIElement to assume.
Int32	finalRectHeight	This is the height that parent or system wants this UIElement to assume.

Remarks

This method internally calls ArrangeOverride override, giving the derived class opportunity to arrange its children and/or content using final computed size. In their ArrangeOverride overrides, derived class is supposed to create its visual structure and prepare itself for rendering. Arrange is called by parents from their implementation of ArrangeOverride or by system when needed. This method sets Bounds=finalSize before calling ArrangeOverride.

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ArrangeOverride(Int32, Int32)

ArrangeOverride allows for the customization of the final sizing and positioning of children.

Declaration

protected virtual void ArrangeOverride(int arrangeWidth, int arrangeHeight)

Parameters

Type	Name	Description
Int32	arrangeWidth	Final width
Int32	arrangeHeight	Final height

Remarks

UIElement authors should override this method, call Arrange on each visible child UIElement, to size and position each child UIElement by passing a rectangle reserved for the child within parent space. Note: It is required that a parent UIElement calls Arrange on each child or they won't be rendered. Typical override follows a pattern roughly like this (pseudo-code):

protected override void ArrangeOverride(int arrangeWidth, int arrangeHeight)
{

foreach (UIElement child in VisualChildren)
{
    child.Arrange(new Rect(childX, childY, childWidth, childHeight);
}
}

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ChildElementFromPoint(Int32, Int32)

Given x, y co-ordinates of the parent UIElement, find the child control that is directly underneath that point. If there are multiple such controls, the one that was created/inserted into the list last wins. This is because we don't have explicit z-ordering right now.

Declaration

public UIElement ChildElementFromPoint(int x, int y)

Parameters

Type	Name	Description
Int32	x
Int32	y

Returns

Type	Description
UIElement

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ContainsPoint(Int32, Int32)

Declaration

public bool ContainsPoint(int x, int y)

Parameters

Type	Name	Description
Int32	x
Int32	y

Returns

Type	Description
Boolean

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GetDesiredSize(out Int32, out Int32)

Declaration

public void GetDesiredSize(out int width, out int height)

Parameters

Type	Name	Description
Int32	width
Int32	height

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GetLayoutOffset(out Int32, out Int32)

Declaration

public void GetLayoutOffset(out int x, out int y)

Parameters

Type	Name	Description
Int32	x
Int32	y

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GetMargin(out Int32, out Int32, out Int32, out Int32)

Declaration

public void GetMargin(out int left, out int top, out int right, out int bottom)

Parameters

Type	Name	Description
Int32	left
Int32	top
Int32	right
Int32	bottom

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GetPointerTarget(Int32, Int32)

Declaration

public UIElement GetPointerTarget(int x, int y)

Parameters

Type	Name	Description
Int32	x
Int32	y

Returns

Type	Description
UIElement

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GetRenderSize(out Int32, out Int32)

Declaration

public void GetRenderSize(out int width, out int height)

Parameters

Type	Name	Description
Int32	width
Int32	height

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GetUnclippedSize(out Int32, out Int32)

Declaration

public void GetUnclippedSize(out int width, out int height)

Parameters

Type	Name	Description
Int32	width
Int32	height

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Invalidate()

Declaration

public void Invalidate()

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InvalidateArrange()

Invalidates the arrange state for the UIElement. The UIElement will be queued for an update layout that will occur asynchronously. MeasureOverride will not be called unless InvalidateMeasure is also called - or that something else caused the measure state to be invalidated.

Declaration

public void InvalidateArrange()

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InvalidateMeasure()

Invalidates the measurement state for the UIElement. This has the effect of also invalidating the arrange state for the UIElement. The UIElement will be queued for an update layout that will occur asynchronously.

Declaration

public void InvalidateMeasure()

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InvalidateRect(Int32, Int32, Int32, Int32)

Declaration

public void InvalidateRect(int x, int y, int w, int h)

Parameters

Type	Name	Description
Int32	x
Int32	y
Int32	w
Int32	h

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Measure(Int32, Int32)

Updates DesiredSize of the UIElement. Must be called by parents from their MeasureOverride, to form recursive update. This is first pass of layout update.

Declaration

public void Measure(int availableWidth, int availableHeight)

Parameters

Type	Name	Description
Int32	availableWidth	Available width that parent can give to the child. May be MaxValue (when parent wants to measure to content). This is soft constraint. Child can return bigger size to indicate that it wants bigger space and hope that parent can throw in scrolling...
Int32	availableHeight	Available height that parent can give to the child. May be MaxValue (when parent wants to measure to content). This is soft constraint. Child can return bigger size to indicate that it wants bigger space and hope that parent can throw in scrolling...

Remarks

Measure is called by parents on their children. Internally, Measure calls MeasureOverride override on the same object, giving it opportunity to compute its DesiredSize.

This method will return immediately if child is not Dirty, previously measured and availableSize is the same as cached.

This method also resets the IsMeasureinvalid bit on the child.

In case when "unbounded measure to content" is needed, parent can use availableSize as double.PositiveInfinity. Any returned size is OK in this case.

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MeasureOverride(Int32, Int32, out Int32, out Int32)

Measurement override. Implement your size-to-content logic here.

Declaration

protected virtual void MeasureOverride(int availableWidth, int availableHeight, out int desiredWidth, out int desiredHeight)

Parameters

Type	Name	Description
Int32	availableWidth	Available size that parent can give to the child. May be MaxValue(when parent wants to measure to content). This is soft constraint. Child can return bigger size to indicate that it wants bigger space and hope that parent can throw in scrolling...
Int32	availableHeight
Int32	desiredWidth
Int32	desiredHeight

Remarks

MeasureOverride is designed to be the main customizability point for size control of layout. UIElement authors should override this method, call Measure on each child UIElement, and compute their desired size based upon the measurement of the children. The return value should be the desired size.

Note: It is required that a parent UIElement calls Measure on each child or they won't be sized/arranged. Typical override follows a pattern roughly like this (pseudo-code):

protected override void MeasureOverride(int avialableWidth, int availableHeight, out int desiredWidth, out int desiredHeight)
{
foreach (UIElement child in VisualChildren)
{
    child.Measure(availableSize);
    availableSize.Deflate(child.DesiredSize);
    _cache.StoreInfoAboutChild(child);
}

Size desired = CalculateBasedOnCache(_cache);
return desired;
}

The key aspects of this snippet are:

You must call Measure on each child UIElement
It is common to cache measurement information between the MeasureOverride and ArrangeOverride method calls
Calling base.MeasureOverride is not required.
Calls to Measure on children are passing either the same availableSize as the parent, or a subset of the area depending on the type of layout the parent will perform (for example, it would be valid to remove the area for some border or padding).

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OnButtonDown(ButtonEventArgs)

Declaration

protected virtual void OnButtonDown(ButtonEventArgs e)

Parameters

Type	Name	Description
ButtonEventArgs	e

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OnButtonUp(ButtonEventArgs)

Declaration

protected virtual void OnButtonUp(ButtonEventArgs e)

Parameters

Type	Name	Description
ButtonEventArgs	e

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OnChildDesiredSizeChanged(UIElement)

Notification that is called by Measure of a child when it ends up with different desired size for the child.

Declaration

protected virtual void OnChildDesiredSizeChanged(UIElement child)

Parameters

Type	Name	Description
UIElement	child

Remarks

Default implementation simply calls invalidateMeasure(), assuming that layout of a parent should be updated after child changed its size.

Finer point: this method can only be called in the scenario when the system calls Measure on a child, not when parent calls it since if parent calls it, it means parent has dirty layout and is recalculating already.

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OnChildrenChanged(UIElement, UIElement, Int32)

OnChildrenChanged is called when the UIElementCollection of the UIElement is edited.

Declaration

protected virtual void OnChildrenChanged(UIElement added, UIElement removed, int indexAffected)

Parameters

Type	Name	Description
UIElement	added
UIElement	removed
Int32	indexAffected

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OnGenericEvent(GenericEventArgs)

Declaration

protected virtual void OnGenericEvent(GenericEventArgs e)

Parameters

Type	Name	Description
GenericEventArgs	e

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OnGotFocus(FocusChangedEventArgs)

Declaration

protected virtual void OnGotFocus(FocusChangedEventArgs e)

Parameters

Type	Name	Description
FocusChangedEventArgs	e

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OnLostFocus(FocusChangedEventArgs)

Declaration

protected virtual void OnLostFocus(FocusChangedEventArgs e)

Parameters

Type	Name	Description
FocusChangedEventArgs	e

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OnPreviewButtonDown(ButtonEventArgs)

Declaration

protected virtual void OnPreviewButtonDown(ButtonEventArgs e)

Parameters

Type	Name	Description
ButtonEventArgs	e

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OnPreviewButtonUp(ButtonEventArgs)

Declaration

protected virtual void OnPreviewButtonUp(ButtonEventArgs e)

Parameters

Type	Name	Description
ButtonEventArgs	e

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OnRender(DrawingContext)

Declaration

public virtual void OnRender(DrawingContext dc)

Parameters

Type	Name	Description
DrawingContext	dc

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OnTouchDown(TouchEventArgs)

Declaration

protected virtual void OnTouchDown(TouchEventArgs e)

Parameters

Type	Name	Description
TouchEventArgs	e

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OnTouchGestureChanged(TouchGestureEventArgs)

Declaration

protected virtual void OnTouchGestureChanged(TouchGestureEventArgs e)

Parameters

Type	Name	Description
TouchGestureEventArgs	e

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OnTouchGestureEnded(TouchGestureEventArgs)

Declaration

protected virtual void OnTouchGestureEnded(TouchGestureEventArgs e)

Parameters

Type	Name	Description
TouchGestureEventArgs	e

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OnTouchGestureStarted(TouchGestureEventArgs)

Declaration

protected virtual void OnTouchGestureStarted(TouchGestureEventArgs e)

Parameters

Type	Name	Description
TouchGestureEventArgs	e

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OnTouchMove(TouchEventArgs)

Declaration

protected virtual void OnTouchMove(TouchEventArgs e)

Parameters

Type	Name	Description
TouchEventArgs	e

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OnTouchUp(TouchEventArgs)

Declaration

protected virtual void OnTouchUp(TouchEventArgs e)

Parameters

Type	Name	Description
TouchEventArgs	e

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PointToClient(ref Int32, ref Int32)

Declaration

public void PointToClient(ref int x, ref int y)

Parameters

Type	Name	Description
Int32	x
Int32	y

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PointToScreen(ref Int32, ref Int32)

We are deviating little from their desktop counter parts, mostly for simplicity and perf.

Declaration

public void PointToScreen(ref int x, ref int y)

Parameters

Type	Name	Description
Int32	x
Int32	y

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RaiseEvent(RoutedEventArgs)

Raise the events specified by RoutedEvent

Declaration

public void RaiseEvent(RoutedEventArgs args)

Parameters

Type	Name	Description
RoutedEventArgs	args	RoutedEventArgs for the event to be raised

Remarks

This method is a shorthand for This method walks up the visual tree, calling cref="UIElement.BuildRouteCore" on every cref="UIElement"

NOTE: The RoutedEvent in RoutedEventArgs and EventRoute must be matched

Once the route is built, it calls InvokeHandlers()

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RenderRecursive(DrawingContext)

Declaration

protected virtual void RenderRecursive(DrawingContext dc)

Parameters

Type	Name	Description
DrawingContext	dc

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SetMargin(Int32)

Declaration

public void SetMargin(int length)

Parameters

Type	Name	Description
Int32	length

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SetMargin(Int32, Int32, Int32, Int32)

Declaration

public void SetMargin(int left, int top, int right, int bottom)

Parameters

Type	Name	Description
Int32	left
Int32	top
Int32	right
Int32	bottom

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UpdateLayout()

Call this method to ensure that the whoel subtree of elements that includes this UIElement is properly updated.

Declaration

public void UpdateLayout()

Remarks

This ensures that UIElements with IsMeasureInvalid or IsArrangeInvalid will get call to their MeasureOverride and ArrangeOverride, and all computed sizes will be validated. This method does nothing if layout is clean but it does work if layout is not clean so avoid calling it after each change in the UIElement tree. It makes sense to either never call it (system will do this in a deferred manner) or only call it if you absolutely need updated sizes and positions after you do all changes.

Events

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IsEnabledChanged

Declaration

public event PropertyChangedEventHandler IsEnabledChanged

Event Type

Type	Description
PropertyChangedEventHandler

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IsVisibleChanged

Declaration

public event PropertyChangedEventHandler IsVisibleChanged

Event Type

Type	Description
PropertyChangedEventHandler

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TouchDown

Declaration

public event TouchEventHandler TouchDown

Event Type

Type	Description
TouchEventHandler

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TouchGestureChanged

Declaration

public event TouchGestureEventHandler TouchGestureChanged

Event Type

Type	Description
TouchGestureEventHandler

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TouchGestureEnd

Declaration

public event TouchGestureEventHandler TouchGestureEnd

Event Type

Type	Description
TouchGestureEventHandler

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TouchGestureStart

Declaration

public event TouchGestureEventHandler TouchGestureStart

Event Type

Type	Description
TouchGestureEventHandler

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TouchMove

Declaration

public event TouchEventHandler TouchMove

Event Type

Type	Description
TouchEventHandler

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TouchUp

Declaration

public event TouchEventHandler TouchUp

Event Type

Type	Description
TouchEventHandler

Extension Methods

LogDispatcher.GetCurrentClassLogger(Object)