当鼠标在panel2上移动时,我需要绘制线条。到目前为止,我已经完成了以下
public Form1()
{
InitializeComponent();
}
private void panel2_Paint(object sender, PaintEventArgs e)
{
if (isDragging)
{
letsPaint(sender, e);
}
}
private void panel2_MouseMove(object sender, MouseEventArgs e)
{
if (isDragging)
{
mouseMoveX = e.X;
mouseMoveY = e.Y;
this.Paint += new PaintEventHandler(panel2_Paint);
}
}
private void letsPaint(object sender, PaintEventArgs e)
{
Pen blackpen = new Pen(Color.Black, 3);
Graphics g = e.Graphics;
g.DrawLine(blackpen, mouseClickedX, mouseClickedY, mouseMoveX, mouseMoveY);
g.Dispose();
}
但是当我移动鼠标时没有任何反应。我想我在这里做错了PaintEventHandler()。请告诉我如何做到这一点,以及是否有更好的方法。
另外我认为我的方法会在表单上绘制,但我需要在panel2上画线。怎么做?提前致谢。
答案 0 :(得分:4)
您无效:
public Form1()
{
InitializeComponent();
panel2.Paint += new letsPaint;
}
private void panel2_MouseMove(object sender, MouseEventArgs e)
{
if (isDragging) {
mouseMoveX = e.X;
mouseMoveY = e.Y;
panel2.Invalidate();
}
}
并且你没有处理图形对象(你没有创建它),但是你做了笔:
private void letsPaint(object sender, PaintEventArgs e) {
using (Pen blackpen = new Pen(Color.Black, 3)) {
e.Graphics.DrawLine(blackpen,
mouseClickedX, mouseClickedY, mouseMoveX, mouseMoveY);
}
}
这是一个使用位图的快速小方法:
Bitmap bmp;
Point lastPoint;
public Form1() {
InitializeComponent();
bmp = new Bitmap(panel1.ClientSize.Width, panel1.ClientSize.Height,
System.Drawing.Imaging.PixelFormat.Format32bppPArgb);
panel1.MouseDown += panel1_MouseDown;
panel1.MouseMove += panel1_MouseMove;
panel1.Paint += panel1_Paint;
}
void panel1_Paint(object sender, PaintEventArgs e) {
e.Graphics.DrawImage(bmp, Point.Empty);
}
void panel1_MouseMove(object sender, MouseEventArgs e) {
if (e.Button == MouseButtons.Left) {
using (Graphics g = Graphics.FromImage(bmp)) {
g.DrawLine(Pens.Black, lastPoint, e.Location);
}
lastPoint = e.Location;
panel1.Invalidate();
}
}
void panel1_MouseDown(object sender, MouseEventArgs e) {
lastPoint = e.Location;
}
这会闪烁,因此您需要使用双缓冲面板更换面板。像这样:
public class PanelEx : Panel {
public PanelEx() {
this.DoubleBuffered = true;
}
}