如何绘制矩形上的MouseDown /移动C# [英] How to draw rectangle on MouseDown/Move c#
问题描述
我不太清楚如何绘制一个矩形(未填写),当我拖我的鼠标按下左侧的同时单击鼠标。
I am not quite sure how to draw a Rectangle (not filled) when I drag my mousedown while left clicking the mouse.
我有这到目前为止
private void canevas_MouseDown( object sender , MouseEventArgs e )
{
if( e.Button == MouseButtons.Left )
{
_topLeft = new Point( e.X , e.Y );
_drawing = true;
}
}
private void canevas_MouseMove( object sender , MouseEventArgs e )
{
if( _drawing )
{
Rectangle rec = new Rectangle( _topLeft.X , _topLeft.Y , ( e.X - _topLeft.X ) , ( e.Y - _topLeft.Y ) );
canevas.CreateGraphics().DrawRectangle( Pens.Black , rec );
}
}
但问题是它,我不希望所有的矩形现身
But the problems it that I dont want all the rectangles to show up
推荐答案
有些code去与Ed的正确答案:
Some code to go with Ed's correct answer:
Point startPos; // mouse-down position
Point currentPos; // current mouse position
bool drawing; // busy drawing
List<Rectangle> rectangles = new List<Rectangle>(); // previous rectangles
private Rectangle getRectangle() {
return new Rectangle(
Math.Min(startPos.X, currentPos.X),
Math.Min(startPos.Y, currentPos.Y),
Math.Abs(startPos.X - currentPos.X),
Math.Abs(startPos.Y - currentPos.Y));
}
private void canevas_MouseDown(object sender, MouseEventArgs e) {
currentPos = startPos = e.Location;
drawing = true;
}
private void canevas_MouseMove(object sender, MouseEventArgs e) {
currentPos = e.Location;
if (drawing) canevas.Invalidate();
}
private void canevas_MouseUp(object sender, MouseEventArgs e) {
if (drawing) {
drawing = false;
var rc = getRectangle();
if (rc.Width > 0 && rc.Height > 0) rectangles.Add(rc);
canevas.Invalidate();
}
}
private void canevas_Paint(object sender, PaintEventArgs e) {
if (rectangles.Count > 0) e.Graphics.DrawRectangles(Pens.Black, rectangles.ToArray());
if (drawing) e.Graphics.DrawRectangle(Pens.Red, getRectangle());
}
要获得canevas具有双缓冲开启,所以它画不闪烁,使用Project +添加新项,选择类并粘贴此code:
To get a 'canevas' that has double-buffering turned on, so it painting doesn't flicker, use Project + Add New Item, select "Class" and paste this code:
using System;
using System.Windows.Forms;
class Canvas : Panel {
public Canvas() {
this.DoubleBuffered = true;
this.SetStyle(ControlStyles.ResizeRedraw, true);
}
}
编译。从工具箱顶部的新控件拖到窗体,取代了原有的canevas。更新相应的事件处理程序。
Compile. Drag the new control from the top of the toolbox onto your form, replacing the original 'canevas'. Update the event handlers accordingly.
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