Question

嗨我正在使用下面的代码在pictureBox上绘制一个圆圈，问题是我不知道为什么有些时候如果我绘制一个圆形它直到我画另一个，有时它会显示第一个圈子。

public partial class Form1 : Form
{
    private bool isMoving = false;
    private Point mouseDownPosition = Point.Empty;
    private Point mouseMovePosition = Point.Empty;
    private List<Tuple<Point, Point>> lines = new List<Tuple<Point, Point>>();
    public Form1()
    {
        InitializeComponent();

        // 
        // pictureBox1
        // 
        this.pictureBox1.Location = new System.Drawing.Point(0, 0);
        this.pictureBox1.Name = "pictureBox1";
        this.pictureBox1.Size = new System.Drawing.Size(231, 235);
        this.pictureBox1.TabIndex = 0;
        this.pictureBox1.TabStop = false;
        this.pictureBox1.Paint += new System.Windows.Forms.PaintEventHandler(this.pictureBox1_Paint);
        this.pictureBox1.MouseDown += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseDown);
        this.pictureBox1.MouseMove += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseMove);
        this.pictureBox1.MouseUp += new System.Windows.Forms.MouseEventHandler(this.pictureBox1_MouseUp);
        this.Controls.Add(this.pictureBox1);
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        var g = e.Graphics;
        if (isMoving)
        {
            g.Clear(pictureBox1.BackColor);
            g.DrawLine(Pens.Black, mouseDownPosition, mouseMovePosition);
            foreach (var line in lines)
            {
                g.DrawLine(Pens.Black, line.Item1, line.Item2);
            }
        }
    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        isMoving = true;
        mouseDownPosition = e.Location;
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (isMoving)
        {
            mouseMovePosition = e.Location;
            pictureBox1.Invalidate();
        }
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        if (isMoving)
        {
            lines.Add(Tuple.Create(mouseDownPosition, mouseMovePosition));
        }
        isMoving = false;
    }
}

Answer 1

使用Refresh()而不是Invalidate()。这将强制调用重新绘制事件。请注意，如果过度重新绘制屏幕，可能会看到性能下降。

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (isMoving)
        {
            mouseMovePosition = e.Location;
            pictureBox1.Refresh();
        }
    }

Answer 2

我在示例中看不到任何圆圈：）

我注意到你的代码表现得有些奇怪，当我添加以下代码时，它似乎让它运行得更好。

  this.pictureBox1.MouseClick += pictureBox1_MouseClick;

...

    void pictureBox1_MouseClick(object sender, MouseEventArgs e)
    {
        isMoving = false;
    }

希望这会有所帮助：）

在C＃PictureBox上画一个圆圈

2 个答案: