4.C#编程学习——窗体Paint事件处理程序

源码

usingSystem;

usingSystem.Drawing;

usingSystem.Windows.Forms;

classPaintEvent

{

   publicstaticvoid Main()

    {

       Form form =newForm();

        form.Text ="Paint Event";

        form.Paint +=newPaintEventHandler(MyPaintHandler);

       Application.Run(form);

    }

   staticvoid MyPaintHandler(object objSender, PaintEventArgs pea)

    {

       Graphics grfx = pea.Graphics;

        grfx.Clear(Color.Chocolate);

    }

}

         当在Main中创建窗体之后，名为MyPaintHandler方法附加到这个窗体的Paint事件中。

         从PaintEventArgs类获得一个Graphics对象，并使用它来调用Clear方法。

Paint事件

         相当频繁、有时出乎意料到调用这个方法。可以不中断的快速重新绘制客户区。

多个窗体

usingSystem;

usingSystem.Drawing;

usingSystem.Windows.Forms;

classPaintTwoForms

{

   staticForm form1, form2;

   publicstaticvoid Main()

    {

        form1 =newForm();

        form2 =newForm();

        form1.Text ="First Form";

        form1.BackColor =Color.White;

        form1.Paint +=newPaintEventHandler(MyPaintHandler);

        form2.Text ="Second Form";

       form2.BackColor =Color.White;

        form2.Paint +=newPaintEventHandler(MyPaintHandler);

        form2.Show();

       Application.Run(form1);

    }

   staticvoid MyPaintHandler(object objSender, PaintEventArgs pea)

    {

       Form form = (Form)objSender;

       Graphics grfx = pea.Graphics;

       string str;

       if (form == form1)

            str ="Hello from the first form";

       else

            str ="Hello from the second form";

        grfx.DrawString(str, form.Font,Brushes.Black, 0, 0);

    }

}

OnPaint方 法

         通过继承Form而不只是创建一个实例可以获得一些好处。

源码

usingSystem;

usingSystem.Drawing;

usingSystem.Windows.Forms;

classHelloWorld :Form

{

   publicstaticvoid Main()

    {

       Application.Run(newHelloWorld());

    }

   public HelloWorld()

    {

        Text ="Hello World";

        BackColor =Color.White;

    }

   protectedoverridevoid OnPaint(PaintEventArgs pea)

    {

       Graphics grfx = pea.Graphics;

        grfx.DrawString("Hello, Windows Forms!", Font,Brushes.Black, 0, 0);

    }

}