永远不会调用OnPaint覆盖

Question

我已经在这几天了,这让我很生气.我有一个继承自System.Windows.Forms.Panel的控件,我试图覆盖OnPaint.它很简单,直截了当地发出它.

public class CollapsiblePanel : System.Windows.Forms.Panel
{
  public CollapsiblePanel()
  {
   //
   // Required for the Windows Form Designer
   //
   InitializeComponent();

   //
   // TODO: Add any constructor code after InitializeComponent call
   //
   SetStyle
    (
     ControlStyles.AllPaintingInWmPaint | 
     ControlStyles.UserPaint      | ControlStyles.DoubleBuffer   |
     ControlStyles.ResizeRedraw     | ControlStyles.Selectable ,
     true
    );
        }

  protected override void OnPaint(PaintEventArgs e)
  {
            // This never runs no matter what I try!
            base.OnPaint(e);
        }
}

Answer 1

当我尝试覆盖OnPaint时,我对ProgressBar也有同样的问题.它从未被调用过.

我在这里找到了解决方案:http://web.archive.org/web/20140214234801/http : //osix.net/modules/article/？id = 826

您必须创建一个构造函数并启用用户绘制,如下所示:

SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.ResizeRedraw, true);

默认值可能因框架版本和操作系统而异.