如何：手动呈现缓冲图形

如果你正在管理自己的缓冲图形，你将需要能创建和程序图形缓冲区。 你可以通过调用 Allocate 方法，在屏幕上创建与绘图图面相关联的 BufferedGraphics 类的实例。 此方法会创建一个与特定呈现图面（如表格或控件）关联的 BufferedGraphics 实例。 在创建 BufferedGraphics 实例后，可以通过 Graphics 属性，将图形绘制到它表示的缓冲区内。 执行所有图形操作之后，可以通过调用 Render 方法将缓冲区的内容复制到屏幕。

手动显示缓冲图形

1. 获取对 BufferedGraphicsContext 类的实例的引用。 有关详细信息，请参阅如何：手动管理缓冲图形。

2. 如下列代码示例所示，通过调用 Allocate 方法，创建 BufferedGraphics 类的实例。

   // This example assumes the existence of a form called Form1.
   BufferedGraphicsContext currentContext;
   BufferedGraphics myBuffer;
   // Gets a reference to the current BufferedGraphicsContext
   currentContext = BufferedGraphicsManager.Current;
   // Creates a BufferedGraphics instance associated with Form1, and with
   // dimensions the same size as the drawing surface of Form1.
   myBuffer = currentContext.Allocate(this.CreateGraphics(),
      this.DisplayRectangle);
   

   ' This example assumes the existence of a form called Form1.
   Dim currentContext As BufferedGraphicsContext
   Dim myBuffer As BufferedGraphics
   ' Gets a reference to the current BufferedGraphicsContext.
   currentContext = BufferedGraphicsManager.Current
   ' Creates a BufferedGraphics instance associated with Form1, and with 
   ' dimensions the same size as the drawing surface of Form1.
   myBuffer = currentContext.Allocate(Me.CreateGraphics, _
      Me.DisplayRectangle)
   
   

3. 通过设置 Graphics 属性将图形绘制到图形缓冲区内。 例如：

   // Draws an ellipse to the graphics buffer.
   myBuffer.Graphics.DrawEllipse(Pens.Blue, this.DisplayRectangle);
   

   ' Draws an ellipse to the graphics buffer.
   myBuffer.Graphics.DrawEllipse(Pens.Blue, Me.DisplayRectangle)
   

4. 当你已完成所有对图形缓冲区的绘制操作时，调用 Render 方法将缓冲区呈现到与该缓冲区关联的绘图图面或指定的绘图图面，如下列代码示例所示。

   // This example assumes the existence of a BufferedGraphics instance
   // called myBuffer.
   // Renders the contents of the buffer to the drawing surface associated
   // with the buffer.
   myBuffer.Render();
   // Renders the contents of the buffer to the specified drawing surface.
   myBuffer.Render(this.CreateGraphics());
   

   ' Renders the contents of the buffer to the drawing surface associated 
   ' with the buffer.
   myBuffer.Render()
   ' Renders the contents of the buffer to the specified drawing surface.
   myBuffer.Render(Me.CreateGraphics)
   

5. 在完成图形呈现后，调用 BufferedGraphics 实例上的 Dispose 方法释放系统资源。

   myBuffer.Dispose();
   

   myBuffer.Dispose()
   

另请参阅

• BufferedGraphicsContext
• BufferedGraphics
• 双缓冲的图形
• 如何：手动管理缓冲的图形