DrawingVisual.RenderOpen 方法

定義

命名空間:

System.Windows.Media

組件:

PresentationCore.dll

開啟用於呈現的 DrawingVisual 物件。 傳回的 DrawingContext 值可用來在 DrawingVisual 中呈現。

public:
 System::Windows::Media::DrawingContext ^ RenderOpen();

public System.Windows.Media.DrawingContext RenderOpen ();

member this.RenderOpen : unit -> System.Windows.Media.DrawingContext

Public Function RenderOpen () As DrawingContext

傳回

DrawingContext

型別 DrawingContext 的值。

範例

在下列範例中，會 DrawingVisual 建立 物件，並傳回物件 DrawingContext 。

// Create a DrawingVisual that contains a rectangle.
private DrawingVisual CreateDrawingVisualRectangle()
{
    DrawingVisual drawingVisual = new DrawingVisual();

    // Retrieve the DrawingContext in order to create new drawing content.
    DrawingContext drawingContext = drawingVisual.RenderOpen();

    // Create a rectangle and draw it in the DrawingContext.
    Rect rect = new Rect(new System.Windows.Point(160, 100), new System.Windows.Size(320, 80));
    drawingContext.DrawRectangle(System.Windows.Media.Brushes.LightBlue, (System.Windows.Media.Pen)null, rect);

    // Persist the drawing content.
    drawingContext.Close();

    return drawingVisual;
}

' Create a DrawingVisual that contains a rectangle.
Private Function CreateDrawingVisualRectangle() As DrawingVisual
    Dim drawingVisual As New DrawingVisual()

    ' Retrieve the DrawingContext in order to create new drawing content.
    Dim drawingContext As DrawingContext = drawingVisual.RenderOpen()

    ' Create a rectangle and draw it in the DrawingContext.
    Dim rect As New Rect(New Point(160, 100), New Size(320, 80))
    drawingContext.DrawRectangle(Brushes.LightBlue, CType(Nothing, Pen), rect)

    ' Persist the drawing content.
    drawingContext.Close()

    Return drawingVisual
End Function

您繪製到繪圖內容的順序很重要- 每個成功的繪圖都會繪製到其他繪圖之上。 在下列範例中，會先繪製矩形，然後繪製文字。

// Retrieve the DrawingContext in order to draw into the visual object.
DrawingContext drawingContext = drawingVisual.RenderOpen();

// Draw a rectangle into the DrawingContext.
Rect rect = new Rect(new Point(160, 100), new Size(320, 80));
drawingContext.DrawRectangle(Brushes.LightBlue, (Pen)null, rect);

// Draw a formatted text string into the DrawingContext.
drawingContext.DrawText(
   new FormattedText("Hello, world",
      CultureInfo.GetCultureInfo("en-us"),
      FlowDirection.LeftToRight,
      new Typeface("Verdana"),
      36, Brushes.Black),
      new Point(200, 116));

// Persist the drawing content.
drawingContext.Close();

' Retrieve the DrawingContext in order to draw into the visual object.
Dim drawingContext As DrawingContext = drawingVisual.RenderOpen()

' Draw a rectangle into the DrawingContext.
Dim rect As New Rect(New Point(160, 100), New Size(320, 80))
drawingContext.DrawRectangle(Brushes.LightBlue, CType(Nothing, Pen), rect)

' Draw a formatted text string into the DrawingContext.
drawingContext.DrawText(New FormattedText("Hello, world", CultureInfo.GetCultureInfo("en-us"), FlowDirection.LeftToRight, New Typeface("Verdana"), 36, Brushes.Black), New Point(200, 116))

' Persist the drawing content.
drawingContext.Close()

備註

當您呼叫 Close 的 DrawingContext 方法時，目前的繪圖內容會取代為 DrawingVisual 定義的任何先前繪圖內容。 這表示無法將新的繪圖內容附加至現有的繪圖內容。

另請參閱

• 使用 DrawingVisuals 範例進行點擊測試