Articolo
11/18/2011

UIElement.Arrange Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Positions child objects and determines a size for a UIElement. Parent objects that implement custom layout for their child elements should call this method from their layout override implementations to form a recursive layout update.

Namespace: System.Windows
Assembly: System.Windows (in System.Windows.dll)

Syntax

'Declaration
Public Sub Arrange ( _
    finalRect As Rect _
)

public void Arrange(
    Rect finalRect
)

Parameters

finalRect
Type: System.Windows.Rect
The final size that the parent computes for the child in layout, provided as a Rect value.

Exceptions

Exception	Condition
InvalidOperationException	finalRect contained a Double.NaN or infinite value. See Remarks.

Remarks

There is no reason to call Measure or Arrange outside of the context of overriding methods that perform custom layout actions. Silverlight layout works autonomously, based on detecting changes to the object tree and layout-relevant properties at run time. For more information, see Silverlight Layout System.

The finalRect you pass to Measure cannot have a Double.NaN value for any Rect value. Also, finalRect cannot have any infinite values for any Rect value.

Typically, calls to Arrange will incorporate a finalRect that uses the height and width values from DesiredSize for each element . Exceptions to this typical behavior might be necessary if an element holds a DesiredSize that the layout parent cannot accommodate, or if the sum total of all child element DesiredSize values cannot be accommodated or arranged. In such cases the child element content might be clipped, resized, or placed in a scroll region, which all depends on the specific functionality that is enabled in the layout parent container.

Examples

The following example shows how you would use Arrange within an ArrangeOverride implementation.

'Second arrange all children and return final size of panel 
Protected Overloads Overrides Function ArrangeOverride(ByVal finalSize As Size) As Size
    'Get the collection of children 
    Dim mychildren As UIElementCollection = Children

    'Get total number of children 
    Dim count As Integer = mychildren.Count

    'Arrange children 
    'We're only allowing 9 children in this panel. More children will get a 0x0 layout slot. 
    Dim i As Integer
    For i = 0 To 8

        'Get (left, top) origin point for the element in the 3x3 block 
        Dim cellOrigin As Point = GetOrigin(i, 3, New Size(100, 100))

        'Arrange child 
        'Get desired height and width. This will not be larger than 100x100 as set in MeasureOverride. 
        Dim dw As Double = mychildren(i).DesiredSize.Width
        Dim dh As Double = mychildren(i).DesiredSize.Height


        mychildren(i).Arrange(New Rect(cellOrigin.X, cellOrigin.Y, dw, dh))
    Next
    For i = 9 To count - 1

        'Give the remaining children a 0x0 layout slot 
        mychildren(i).Arrange(New Rect(0, 0, 0, 0))
    Next


    'Return final size of the panel 
    Return New Size(300, 300)
End Function

'Calculate point origin of the Block you are in 
Protected Function GetOrigin(ByVal blockNum As Integer, ByVal blocksPerRow As Integer, ByVal itemSize As Size) As Point
    'Get row number (zero-based) 
    Dim row As Integer = CInt(Math.Floor(blockNum / blocksPerRow))

    'Get column number (zero-based) 
    Dim column As Integer = blockNum - blocksPerRow * row

    'Calculate origin 
    Dim origin As New Point(itemSize.Width * column, itemSize.Height * row)
    Return origin

End Function

// Second arrange all children and return final size of panel
protected override Size ArrangeOverride(Size finalSize)
{
    // Get the collection of children
    UIElementCollection mychildren = Children;

    // Get total number of children
    int count = mychildren.Count;

    // Arrange children
    // We're only allowing 9 children in this panel.  More children will get a 0x0 layout slot.
    int i;
    for (i = 0; i < 9; i++)
    {

        // Get (left, top) origin point for the element in the 3x3 block
        Point cellOrigin = GetOrigin(i, 3, new Size(100, 100));

        // Arrange child
        // Get desired height and width. This will not be larger than 100x100 as set in MeasureOverride.
        double dw = mychildren[i].DesiredSize.Width;
        double dh = mychildren[i].DesiredSize.Height;

        mychildren[i].Arrange(new Rect(cellOrigin.X, cellOrigin.Y, dw, dh));

    }

    // Give the remaining children a 0x0 layout slot
    for (i = 9; i < count; i++)
    {
        mychildren[i].Arrange(new Rect(0, 0, 0, 0));
    }


    // Return final size of the panel
    return new Size(300, 300);
}

// Calculate point origin of the Block you are in
protected Point GetOrigin(int blockNum, int blocksPerRow, Size itemSize)
{
    // Get row number (zero-based)
    int row = (int)Math.Floor(blockNum / blocksPerRow);

    // Get column number (zero-based)
    int column = blockNum - blocksPerRow * row;

    // Calculate origin
    Point origin = new Point(itemSize.Width * column, itemSize.Height * row);
    return origin;

}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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