它正在到达F_Paint事件，但没有到达F_MouseDown事件。我想在F表格上画矩形。
也许因为F表单是透明的，所以它不能在上面绘制？但它永远不会到达F_MouseDown事件，我在F_MouseDown事件中使用了一个断点。
不确定为什么没有进入MouseDown事件。
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace Tester
{
public partial class Form1 : Form
{
Ffmpeg ffmpeg = new Ffmpeg();
private bool _canDraw;
private int _startX, _startY;
private Rectangle _rect;
public Form1()
{
InitializeComponent();
BackColor = Color.Blue;
TransparencyKey = BackColor;
Opacity = 1;
var f = new HelperForm { Opacity = 0, ShowInTaskbar = false, FormBorderStyle = FormBorderStyle.None };
f.MouseDown += F_MouseDown;
f.MouseMove += F_MouseMove;
f.MouseUp += F_MouseUp;
f.Paint += F_Paint;
f.Show();
Visible = false;
Owner = f;
Visible = true;
Move += (o, a) => f.Bounds = Bounds;
Resize += (o, a) => f.Bounds = Bounds;
f.Bounds = Bounds;
ffmpeg.Start(@"d:ffmpegx86test.mp4", 24);
}
private void F_Paint(object sender, PaintEventArgs e)
{
//Create a new 'pen' to draw our rectangle with, give it the color red and a width of 2
using (Pen pen = new Pen(Color.Red, 2))
{
//Draw the rectangle on our form with the pen
e.Graphics.DrawRectangle(pen, _rect);
}
}
private void F_MouseUp(object sender, MouseEventArgs e)
{
//The system is no longer allowed to draw rectangles
_canDraw = false;
}
private void F_MouseMove(object sender, MouseEventArgs e)
{
//If we are not allowed to draw, simply return and disregard the rest of the code
if (!_canDraw) return;
//The x-value of our rectangle should be the minimum between the start x-value and the current x-position
int x = Math.Min(_startX, e.X);
//The y-value of our rectangle should also be the minimum between the start y-value and current y-value
int y = Math.Min(_startY, e.Y);
//The width of our rectangle should be the maximum between the start x-position and current x-position minus
//the minimum of start x-position and current x-position
int width = Math.Max(_startX, e.X) - Math.Min(_startX, e.X);
//For the hight value, it's basically the same thing as above, but now with the y-values:
int height = Math.Max(_startY, e.Y) - Math.Min(_startY, e.Y);
_rect = new Rectangle(x, y, width, height);
//Refresh the form and draw the rectangle
Refresh();
}
private void F_MouseDown(object sender, MouseEventArgs e)
{
//The system is now allowed to draw rectangles
_canDraw = true;
//Initialize and keep track of the start position
_startX = e.X;
_startY = e.Y;
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
ffmpeg.Close();
}
}
class HelperForm : Form
{
protected override CreateParams CreateParams
{
get
{
const int WS_EX_TOOLWINDOW = 0x80;
CreateParams cp = base.CreateParams;
cp.ExStyle |= WS_EX_TOOLWINDOW;
return cp;
}
}
}
}
有几个原因阻止绘制矩形并触发鼠标事件。首先，将Opacity设置为0；这意味着，无论你想画什么，都永远看不见。相反，您应该将TransparencyKey设置为BackColor:中的颜色
f.TransparencyKey = f.BackColor;
然后，您尝试使用从未初始化过的对象_rect绘制一个矩形；因此，您试图绘制的矩形将以0宽0高的大小绘制，这意味着它不会被绘制，因此，在初始化过程中，您应该为_rect提供一个默认值，例如：
_rect = new Rectangle(Point.Empty, this.Size);
绘制的矩形现在应该是可见的；然而，事件不会触发，因为你正在反转表单所有权，所以，不是
Owner = f;
用途：
f.Owner = this;