处理静电刷

Question

我正在写一个生物节律应用程序.为了测试它,我有一个带有Button和PictureBox的表单.当我点击按钮时,我做了

myPictureBox.Image = GetBiorhythm2();

哪个第一次运行正常,但在第二次单击时会导致以下异常:

System.ArgumentException: Parameter is not valid.
   at System.Drawing.Graphics.CheckErrorStatus
   at System.Drawing.Graphics.FillEllipse
   at Larifari.Biorhythm.Biorhythm.GetBiorhythm2 in c:\delo\Horoskop\Biorhythm.cs:line 157
   at Larifari.test.Button1Click in c:\delo\Horoskop\test.Designer.cs:line 169
   at System.Windows.Forms.Control.OnClick
   at System.Windows.Forms.Button.OnClick
   at System.Windows.Forms.Button.OnMouseUp
   at System.Windows.Forms.Control.WmMouseUp
   at System.Windows.Forms.Control.WndProc
   at System.Windows.Forms.ButtonBase.WndProc
   at System.Windows.Forms.Button.WndProc
   at ControlNativeWindow.OnMessage
   at ControlNativeWindow.WndProc
   at System.Windows.Forms.NativeWindow.DebuggableCallback
   at ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop
   at ThreadContext.RunMessageLoopInner
   at ThreadContext.RunMessageLoop
   at System.Windows.Forms.Application.Run
   at Larifari.test.Main in c:\delo\Horoskop\test.cs:line 20

导致错误的减少功能是:

public static Image GetBiorhythm2() {
        Bitmap bmp = new Bitmap(600, 300);
        Image img = bmp;
        Graphics g = Graphics.FromImage(img);

        Brush brush = Brushes.Black;
        g.FillEllipse(brush, 3, 3, 2, 2); //Here the exception is thrown on the second call to the function

        brush.Dispose(); //If i comment this out, it works ok.

        return img;
 }

如果我评论刷子处理它可以正常工作,但我对此并不满意,并希望找到一个替代解决方案.你能帮我吗 ？

Answer 1

Bruhes.Black是一种系统资源,不适合您处置.运行时管理Brushes类,Pens和其他此类对象中的画笔.它根据需要创建和处理这些对象,使常用项目保持活动状态,以便不必持续创建和销毁它们.

Brushes类的文档说:

Brushes类包含静态只读属性,这些属性返回由属性名称指示的颜色的Brush对象.除非用于构造新画笔,否则通常不必显式处理此类中属性返回的画笔.

简而言之,不要在系统提供的对象上调用Dispose.

Answer 2

看起来你正试图处理静态,这会在下次使用时导致一些问题:

    Brush brush = Brushes.Black;
    g.FillEllipse(brush, 3, 3, 2, 2); //Here the exception is thrown on the second call to the function

    brush.Dispose(); //If i comment this out, it works ok.

当你设置brush = Brushes.Black时,你实际上是将画笔设置为静态Brushes.Black的引用(或指针).通过处理它,你有效地写作:

    Brushes.Black.dispose();

当你回来再次使用黑色画笔时,运行时说你不能,因为它已被处理掉,并且不是g.FillEllipse()的有效参数

写这个的更好方法可能只是:

    g.FillEllipse(Brushes.Black, 3, 3, 2, 2);

或者,如果你想要真的很复杂:

    Brush brush = Brushes.Black.Clone();
    g.FillEllipse( brush, 3, 3, 2, 2 );
    brush.Dispose();

或者如果你不关心看错的东西,只需注释掉brush.Dispose(); 原始代码中的行.