递归中的stackoverflow
本文关键字：stackoverflow 递归 | 更新日期: 2023-09-27 18:24:17
我正在制作一个ms paint应用程序，它在里面绘制conture和fill。我写了一个递归函数来填充conture。它工作得很好，但如果污染太大，程序会抛出stackerflow异常。我该如何解决这个问题？？我甚至抓不到这个异常（
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
[DllImport( "user32.dll" )]
static extern IntPtr GetDC( IntPtr hWnd );
[DllImport( "user32.dll" )]
static extern int ReleaseDC( IntPtr hWnd, IntPtr hDC );
[DllImport( "gdi32.dll" )]
static extern int GetPixel( IntPtr hDC, int x, int y );
[DllImport( "gdi32.dll" )]
static extern int SetPixel( IntPtr hDC, int x, int y, int color );
static public Color GetPixel( Control control, int x, int y )
{
Color color = Color.Empty;
if (control != null)
{
IntPtr hDC = GetDC( control.Handle );
int colorRef = GetPixel( hDC, x, y );
color = Color.FromArgb(
(int)(colorRef & 0x000000FF),
(int)(colorRef & 0x0000FF00) >> 8,
(int)(colorRef & 0x00FF0000) >> 16 );
ReleaseDC( control.Handle, hDC );
}
return color;
}
static public void SetPixel( Control control, int x, int y, Color color )
{
if (control != null)
{
IntPtr hDC = GetDC( control.Handle );
int argb = color.ToArgb();
int colorRef =
(int)((argb & 0x00FF0000) >> 16) |
(int)(argb & 0x0000FF00) |
(int)((argb & 0x000000FF) << 16);
SetPixel( hDC, x, y, colorRef );
ReleaseDC( control.Handle, hDC );
}
}
int oldX, oldY;
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
Graphics g = panel1.CreateGraphics();
g.Clear(panel1.BackColor);
}
bool paint;
private void Form1_Load(object sender, EventArgs e)
{
}
private void panel1_MouseDown(object sender, MouseEventArgs e)
{
oldX = e.X;
oldY = e.Y;
paint = true;
}
private void panel1_MouseUp(object sender, MouseEventArgs e)
{
paint = false;
}
private void panel1_MouseMove(object sender, MouseEventArgs e)
{
if (paint)
{
Graphics g = panel1.CreateGraphics();
Pen p = new Pen(Color.Black);
g.DrawLine(p, oldX, oldY, e.X, e.Y);
oldX = e.X;
oldY = e.Y;
}
}
private void panel1_MouseDoubleClick(object sender, MouseEventArgs e)
{
fill(e.X, e.Y, Color.Black, Color.Red);
Color c = GetPixel(panel1, e.X, e.Y);
ClearButton.BackColor = c;
label1.Text = e.X + " " + e.Y;
}
private void fill(int x, int y, Color border, Color c) {
Color PointedColor = GetPixel(panel1, x, y);
try {
if (PointedColor.R != border.R && PointedColor.G != border.G && PointedColor.B != border.B &&
PointedColor.R != c.R && PointedColor.G != c.G && PointedColor.B != c.B &&
x >= 0 && x < panel1.Size.Width && y >= 0 && y < panel1.Size.Height)
{
SetPixel(panel1, x, y, c);
fill(x - 1, y, border, c);
fill(x + 1, y, border, c);
fill(x, y - 1, border, c);
fill(x, y + 1, border, c);
}
}
catch(System.StackOverflowException e)
{
label1.Text = e.Message;
}
}
}
}
您应该使用非递归洪泛填充算法。
有关描述，请参阅维基百科文章
Bob Powell在这里有一些源代码。
请注意，试图通过每次创建一个新线程来解决当前堆栈溢出的问题是一个非常昂贵的解决方案：使用简单的非递归解决方案肯定是更好的方法。创建额外的线程来克服堆栈问题而不是正确使用线程。如果您认为通过使用多个线程可以获得更好的性能，那么即使这样，您也应该使用非递归解决方案。
设计时不允许捕获StackOverflowException：
从.NET Framework 2.0版本开始，尝试捕获块无法捕获
StackOverflowException对象，并且默认情况下会终止相应的进程。因此，建议用户编写代码以检测并防止堆栈溢出。例如，如果应用程序依赖于递归，请使用计数器或状态条件终止递归循环。
我相信有更有效的方法来实现这一点。然而，首先，您可以将调用堆栈具体化为Stack<T>:，从而将递归转换为迭代
private void fill(int xInitial, int yInitial, Color border, Color c)
{
var remaining = new Stack<Tuple<int, int>>();
remaining.Push(Tuple.Create(xInitial, yInitial));
while (remaining.Any())
{
var next = remaining.Pop();
int x = next.Item1;
int y = next.Item2;
Color PointedColor = GetPixel(panel1, x, y);
if (PointedColor.R != border.R &&
PointedColor.G != border.G &&
PointedColor.B != border.B &&
PointedColor.R != c.R &&
PointedColor.G != c.G &&
PointedColor.B != c.B &&
x >= 0 &&
x < panel1.Size.Width &&
y >= 0 &&
y < panel1.Size.Height)
{
SetPixel(panel1, x, y, c);
remaining.Push(Tuple.Create(x - 1, y));
remaining.Push(Tuple.Create(x + 1, y));
remaining.Push(Tuple.Create(x, y - 1));
remaining.Push(Tuple.Create(x, y + 1));
}
}
}