winforms 尝试在C#表单中设计Square的预览

kh212irz 于 7个月前发布在 C#

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的数据
我试图创建一个通过拖动鼠标，而被点击一个正方形，我可以单独创建squaure，但不能使它与预览工作。虽然它被拖动预览形状不被删除的某些原因，我真的不明白为什么会发生这种情况。我将包括图片和视频发生这种情况，因为它是有点难以解释它的文字。
Preview是如何工作的：有2笔，一个是用来擦除正在创建的形状，而光标通过形式旅行，直到它是让小康和广场的设计

public partial class Form1 : Form
{
    Pen pen, eraser;
    Graphics graphics;
    Bitmap bitmap;
    Point startPoint, endPoint;
    int choice;
    Boolean draw;
    int width;
    int height;
    public Form1()
    {
        InitializeComponent();
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        if (draw && choice == 1)
        {
            width = e.Location.X - startPoint.X;
            height = e.Location.Y - startPoint.Y;
            width = height;
            Rectangle shape = new Rectangle(startPoint.X, startPoint.Y, width, height);
            graphics.DrawRectangle(pen, shape);
            pictureBox1.Refresh();
            draw = false;
        }
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (draw && choice == 1)
        {
            width = e.Location.X - startPoint.X;
            height = e.Location.Y - startPoint.Y;
            width = height;
            graphics.DrawRectangle(eraser, startPoint.X, startPoint.Y, width, height);
            graphics.DrawRectangle(pen, startPoint.X, startPoint.Y, width, height);
            pictureBox1.Refresh();
        }
    }


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

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winforms

来源：https://stackoverflow.com/questions/77484366/trying-to-design-the-preview-of-a-square-in-a-c-sharp-form

1条答案

按热度按时间

vktxenjb1#

您的代码采用了次优方法。当您想要在PictureBox上绘制时，您可以调用pictureBox1.Refresh() * 或 * 您可以Invalidate部分或全部ClientRectangle。PictureBox通过创建Graphics上下文并触发Paint事件来响应，从而为您提供可以绘制的机会和边界。
需要注意的是，操作系统会告诉PictureBox在其他不同的时间进行重绘，而不一定是响应您的请求，例如当控件或其父控件调整大小时。如果您的绘图代码“在其他地方”，并且不包含在OnPaint事件处理程序中，那么您在表面上绘制的任何内容都将被删除。
你帖子中的图片证明了你的方法出了严重的问题。每次调用Invalidate时，你都会得到一个新的画布来绘制，如下所示。“擦除”任何东西都是完全不必要的，以至于如果你想保留以前绘制的方块，你必须将它们保存在某种文档中（参见下面的RectanglesToRedraw）。

的数据

public partial class MainForm : Form
{
    public MainForm()
    {
        InitializeComponent();

        // Capture starting point.
        pictureBox1.MouseDown += (sender, e) =>
            _mouseDownPoint = e.Location;

        // If Left button is down, tell the picture box to repaint itself.
        pictureBox1.MouseMove += (sender, e) =>
        {
            if (e.Button == MouseButtons.Left)
            {
                _mouseCurrentPoint = e.Location;
                pictureBox1.Invalidate();
            }
        };

        // Use the Paint event to draw.
        pictureBox1.Paint += (sender, e) =>
        {
            if (MouseButtons == MouseButtons.Left)
            {
                using (var pen = new Pen(Color.DarkRed, 2F))
                {
                    Debug.WriteLine($"{_mouseDownPoint}{_mouseCurrentPoint}");
                    var width = _mouseCurrentPoint.X - _mouseDownPoint.X;
                    var height = _mouseCurrentPoint.Y - _mouseDownPoint.Y;
                    var side = Math.Max(width, height);

                    // Draw rectangle ON THE GRAPHICS PROVIDED.
                    _currentBounds = new Rectangle(_mouseDownPoint, new Size(side, side));
                    e.Graphics.DrawRectangle(pen, _currentBounds);

                    foreach (var savedRectangle in RectanglesToRedraw)
                    {
                        e.Graphics.DrawRectangle(pen, savedRectangle);                           
                    }
                }
            }
        };

        // If you don't want this square to erase the next
        // time you Invalidate, add it to your "Document".
        pictureBox1.MouseUp += (sender, e) => 
            RectanglesToRedraw.Add(_currentBounds);
    }
    Point _mouseDownPoint = default;
    Point _mouseCurrentPoint = default;
    Rectangle _currentBounds = default;
    List<Rectangle> RectanglesToRedraw { get; } = new List<Rectangle>();
}

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winforms 尝试在C#表单中设计Square的预览

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