如何：手动呈现缓冲图形

如果要管理自己的缓冲图形，则需要能够创建和呈现图形缓冲区。 通过调用Allocate方法，可以创建与屏幕上绘图图面关联的BufferedGraphics类的实例。 此方法创建与 BufferedGraphics 特定呈现图面（如窗体或控件）关联的实例。 创建 BufferedGraphics 实例后，可以将图形绘制到它通过属性表示的 Graphics 缓冲区。 执行所有图形作后，可以通过调用 Render 该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. 通过调用Allocate方法创建类的BufferedGraphics实例，如以下代码示例所示。

   // 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。 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. 完成图形缓冲区的所有绘图操作后，调用 Render 方法将缓冲区渲染到与该缓冲区关联的绘图图面或指定的绘图图面，如以下代码示例所示。

   // 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. 完成图形呈现后，在 BufferedGraphics 实例上调用 Dispose 方法以释放系统资源。

   myBuffer.Dispose();
   

   myBuffer.Dispose()
   

另请参阅

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