狗的速度相同

Question

我正在开发第一个C#头实验室.我在程序中遇到了一个问题,那就是狗的速度相同.我无法弄清楚他们为什么会这样做,因为在我看来,每个对象实例都会在其X位置添加一个随机的1到5个像素.这种随机性应该足以产生差异.

所以,因为我不想发布我的整套实验室1类,我重新创建了一个小型独立版本,只有两只狗赛车,没有下注方面.

Form1.Designer包含: - 两个带有猎犬的图片框.-a开始按钮

Greyhound.cs类:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing;

namespace test
{
    public class Greyhound
    {
        public int DogID;
        public PictureBox myPictureBox;
        public Point StartingPosition;
        public Point CurrentPosition;
        public Random Randomizer;

        public bool Run()
        {
            int AddDistance = Randomizer.Next(1, 7);
            CurrentPosition.X += AddDistance;
            myPictureBox.Location = CurrentPosition;

            if (CurrentPosition.X > 600)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        public void ReturnToStart()
        {
            CurrentPosition = StartingPosition;
            myPictureBox.Location = StartingPosition;
        }
    }
}

Form1.cs类:

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;

namespace test
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            Greyhound One = new Greyhound() { DogID = 1, myPictureBox = pictureBox1, StartingPosition = pictureBox1.Location, CurrentPosition = pictureBox1.Location, Randomizer = new Random() };
            Greyhound Two = new Greyhound() { DogID = 2, myPictureBox = pictureBox2, StartingPosition = pictureBox1.Location, CurrentPosition = pictureBox2.Location, Randomizer = new Random() };
            if (One.Run())
            {
                timer1.Enabled = false;
                MessageBox.Show("Dog One WON!");

            }
            else if (Two.Run())
            {
                timer1.Enabled = false;
                MessageBox.Show("Dog Two WON!");
            }


        }

        private void button1_Click(object sender, EventArgs e)
        {
            timer1.Enabled = true;
        }
    }
}

任何人都可以看到这个创建的方式有问题吗？为什么狗会以相同的速度运行而不是每次随机1到5个像素的原因.

Answer 1

不要将新的 Random 传递给每只狗，而是这样做：

Random rnd = new Random();
Greyhound One = new Greyhound() { DogID = 1, myPictureBox = pictureBox1, StartingPosition = pictureBox1.Location, CurrentPosition = pictureBox1.Location, Randomizer = rnd };
Greyhound Two = new Greyhound() { DogID = 2, myPictureBox = pictureBox2, StartingPosition = pictureBox1.Location, CurrentPosition = pictureBox2.Location, Randomizer = rnd  };

解释
发生这种情况是因为随机对象实际上是半随机的，它们生成使用给定种子数计算的随机数序列。如果您使用 Random() 构造函数，则该种子会在运行时自动生成。但是，如果您按顺序创建两个随机数，就像您在代码中所做的那样，生成的种子将相等，两个随机发生器生成的数字也将相等。

您可以尝试使用更简单的示例：

        //Your two dogs have two new Random instantiated in sequence.
        //The two random numbers will be always the same
        bool areTheSame = new Random().Next() == new Random().Next();
        Console.WriteLine("two dogs with two Random are the same? "+ areTheSame);
        Random rnd = new Random();

        //The two dogs have now the same random object.
        //The two random numbers will be almost always different. Almost because the numbers are random and two or more equals number can occur in sequence.
        areTheSame = rnd.Next() == rnd.Next();
        Console.WriteLine("two dogs using the same random are the same? ~" + areTheSame);
        Console.ReadLine();