如何通过鼠标从任何坐标通过代码绘制矩形 [英] how to draw a rectangle by mouse through code from any co-ordinates

问题描述

仅当我从左上角拖动时，我的程序才通过代码绘制矩形.
我希望它可以从任何侧面拖动鼠标.

我正在使用

My program draws rectangle through code only when i drag from upper-left corner.
I want it to be from any side i drag the mouse.

I''m using

CreateGraphic.DrawRectangle(pen,rectangle);

推荐答案

，您需要处理四个事件，要绘制的表单或面板:

You need to handle four events, either for the Form you want to draw on, or a Panel instead:

MouseDown
MouseMove
MouseUp
Paint

声明三个类级别的变量:

Declare three class level variables:

private bool drawBox = false;
private Point start;
private Point end;

处理Paint事件:

Handle the Paint event:

private void myPanel_Paint(object sender, PaintEventArgs e)
    {
    if (start != null && end != null)
        {
        int mnX = Math.Min(start.X, end.X);
        int mnY = Math.Min(start.Y, end.Y);
        int mxX = Math.Max(start.X, end.X);
        int mxY = Math.Max(start.Y, end.Y);
        e.Graphics.DrawRectangle(Pens.Black, mnX, mnY, mxX - mnX, mxY - mnY);
        }
    }

并处理鼠标事件:

And handle the mouse events:

private void myPanel_MouseDown(object sender, MouseEventArgs e)
    {
    drawBox = true;
    start = e.Location;
    end = start;
    myPanel.Invalidate();
    }

private void myPanel_MouseMove(object sender, MouseEventArgs e)
    {
    if (drawBox)
        {
        end = e.Location;
        myPanel.Invalidate();
        }
    }

private void myPanel_MouseUp(object sender, MouseEventArgs e)
    {
    drawBox = false;
    }

我自己也以类似的方式解决了它.但是现在在绘制时它会闪烁很多.
我重写方法OnPaintBackgound()并将其留空.这样可以避免完全闪烁，但是会禁用表单背景和其他控件.它变得透明.

谁能建议解决方案...

I solved it myself in a similar way.. But now while drawing it flickers a lot..

i override the method OnPaintBackgound() and left it empty. This avoids flickering completely but form background and other controls are disabled.. It becomes transparent.

Can anyone suggest a solution ...

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