你知道这是什么原因吗？

Question

public partial class Form1 : Form
    {
        Point prePoint, curPoint;
        int PointNumber = 0;
        MOUSE_STATE mouse_state;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            pictureBox1.Image = Image.FromFile("D:\\签名系统\\图片resouce\\底图.jpg");
            this.WindowState = FormWindowState.Maximized;
        }

        private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {
            textBox1.Text = PointNumber.ToString();
            if (mouse_state == MOUSE_STATE.MOUSE_STATE_DOWN)
            {
                curPoint = Control.MousePosition;
                if (prePoint == curPoint)
                {
                    MessageBox.Show("相等");
                }
                PointNumber++;
                if (2 == PointNumber)
                {
                    prePoint = curPoint;
                }
                else if (3 == PointNumber)
                {
                    prePoint = curPoint;
                }
                else if (4 == PointNumber)
                {
                    prePoint = curPoint;
                    PointNumber = 2;
                }
            }
          
        }

        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            PointNumber = 1;
            prePoint = Control.MousePosition;
            mouse_state = MOUSE_STATE.MOUSE_STATE_DOWN;
        }

        private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {
            PointNumber = 0;
            mouse_state = MOUSE_STATE.MOUSE_STATE_UP;
        }
    }
    public enum MOUSE_STATE
    { 
        MOUSE_STATE_UP,
        MOUSE_STATE_DOWN
    }

按照逻辑应该不会打印出“相等吧”，在什么条件下才促使if(prePoint==curPoint)成立的呢?

在移动鼠标的过程中打印出“相等”的情况很少？哪位帮忙看看呀

Answer 1

没有人知道么？

Answer 2

因为这代码在呼叫pictureBox1_MouseDown 之后必须要在移动后才会再次呼叫pictureBox1_MouseMove，如此一来位置一定不对，可以使用以下代码观察：

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    textBox1.Text = PointNumber.ToString();
    if (mouse_state == MOUSE_STATE.MOUSE_STATE_DOWN)
    {
        curPoint = Control.MousePosition;
        textBox3.Text = "X: " + curPoint.X + "; Y: " + curPoint.Y;
        textBox2.Text = "X: " + prePoint.X + "; Y: " + prePoint.Y; 
        if (prePoint == curPoint)
        {
            MessageBox.Show("相等");
        }
        PointNumber++;
        if (2 == PointNumber)
        {
            prePoint = curPoint;
        }
        else if (3 == PointNumber)
        {
            prePoint = curPoint;
        }
        else if (4 == PointNumber)
        {
            prePoint = curPoint;
            PointNumber = 2;
        }
    }
}

这样你就会知道为什么会不对了。

如果你需要pictureBox1_MouseDown 后位置相同，我建议直接将按钮事件带入pictureBox1_MouseMove。

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
    PointNumber = 1;
    prePoint = Control.MousePosition;
    mouse_state = MOUSE_STATE.MOUSE_STATE_DOWN;
    pictureBox1_MouseMove(sender, e);
}

Answer 3

我还是不懂为什么会相等，我就是想只在鼠标移动的时候才进行一些运算啊，如果我鼠标不移动，就不会进行MouseMove里面的代码呀，一旦鼠标移动curPoint就被赋予了另一个Control.MousePosition值，就不可能和之前的MousePosition相等了呀