C#Drawing Rectangle鼠标事件

Question

我想画一个矩形.我想要的是向用户显示鼠标事件上的矩形.

就像在图像中.这适用于C#.net Forms应用程序.

帮助我实现这一目标.任何帮助表示赞赏.

谢谢Yohan

Answer 1

您可以分三步完成:

• 首先检查是否按下了鼠标
• 如果是鼠标移动事件,则在拖动鼠标时继续使用新位置初始化矩形
• 然后在paint事件上绘制矩形.(几乎每个鼠标事件都会引发,取决于鼠标刷新率和dpi)

你可以做这样的事情(在你的Form):

public class Form1
{

       Rectangle mRect;

    public Form1()
    {
                    InitializeComponents();

                    //Improves prformance and reduces flickering
        this.DoubleBuffered = true;
    }

            //Initiate rectangle with mouse down event
    protected override void OnMouseDown(MouseEventArgs e)
    {
        mRect = new Rectangle(e.X, e.Y, 0, 0);
        this.Invalidate();
    }

            //check if mouse is down and being draged, then draw rectangle
    protected override void OnMouseMove(MouseEventArgs e)
    {
        if( e.Button == MouseButtons.Left)
        {
            mRect = new Rectangle(mRect.Left, mRect.Top, e.X - mRect.Left, e.Y - mRect.Top);
            this.Invalidate();
        }
    }

            //draw the rectangle on paint event
    protected override void OnPaint(PaintEventArgs e)
    {
                //Draw a rectangle with 2pixel wide line
        using(Pen pen = new Pen(Color.Red, 2))
        {
        e.Graphics.DrawRectangle(pen, mRect);
        }

    }
}

稍后如果要检查按钮(如图所示)是否为矩形,可以通过检查按钮的区域并检查它们是否位于绘制的矩形中来实现.