我的第一个 c# 应用程序和第一个空对象异常
本文关键字:第一个 对象 异常 应用程序 我的 | 更新日期: 2023-09-27 18:37:27
这里的菜鸟总数。这是我第一次尝试 c#,它是一个控制台应用程序,模拟一个名为"左右中心"的饮酒游戏。在控制台中,我收到以下内容:
安慰
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
at LeftRightCenter.MainClass.Main (System.String[] args) [0x00038] in /Users/apple/Projects/LearningC/LearningC/Main.cs:80
C#
using System;
namespace LeftRightCenter
{
class Player
{
//fields
private int _quarters = 4;
public int Quarters {
get{ return _quarters; }
set{ _quarters += value; }
}
public Player (string name)
{
}
}
class Dice
{
Random random = new Random();
public int Roll ()
{
random = new Random ();
int diceSide;
diceSide = random.Next (0, 6);
diceSide = (diceSide > 2) ? 3 : diceSide;
return diceSide;
}
}
class MainClass
{
static int activePlayer = 0;
static int theCup = 0;
static Player[] thePlayers = {
new Player ("Jessica"),
new Player ("Isaac"),
new Player ("Ed"),
new Player ("Bella"),
new Player ("Elisa"),
new Player ("Fake RedHead"),
new Player ("Linda"),
new Player ("MJ"),
new Player ("Irene"),
new Player("Devin")
};
static Dice[] theDice = new Dice[2];
private static void MoveQuarter (int direction)
{
int numberOfPlayers = thePlayers.Length - 1;
switch (direction) {
case 0:
thePlayers [activePlayer].Quarters = -1;
theCup++;
break;
case 1:
thePlayers [activePlayer].Quarters = -1;
int leftPlayer = (activePlayer == 0) ? numberOfPlayers : activePlayer - 1;
thePlayers [leftPlayer].Quarters = +1;
break;
case 2:
thePlayers [activePlayer].Quarters = -1;
int rightPlayer = (activePlayer == numberOfPlayers) ? 0 : activePlayer + 1;
thePlayers [rightPlayer].Quarters = +1;
break;
}
}
public static void Main (string[] args)
{
int cupEndPoint = thePlayers.Length * 4 - 1;
while (theCup < cupEndPoint) {
foreach (Dice rattle in theDice) {
if (thePlayers [activePlayer].Quarters > 0) {
MoveQuarter (rattle.Roll ()); // this line seems to be the problem
}
}
Console.WriteLine ("{0} Quarters In the Cup", theCup);
}
}
}
}
我不知道问题是什么或为什么,我的谷歌搜索已被证明更多的是令人困惑而不是有用。
对于那些好奇的人,我现在几乎没有实验工作
http://pastebin.com/jxCCW2cd
此行
static Dice[] theDice = new Dice[2];
声明一个数组,该数组允许存储 Dice 类的 2 个对象,但此数组中的每个值仍为 null。
您需要在数组的每个插槽上创建一个骰子,然后再在 Main 方法内的 foreach 循环中使用它。
theDice[0] = new Dice();
theDice[1] = new Dice();
如果停止该行的调试器
MoveQuarter (rattle.Roll ());
您将看到rattle
骰子为空。
编辑:查看您的代码,我发现了一个有问题的情况在 Roll 方法中,您重新创建随机生成器,这对随机性没有好处。(请参阅本问题中接受的答案)
最后,Dice 数组可以像您已经为 Player 数组所做的那样创建和初始化
static Dice[] theDice = new Dice[2] {new Dice(), new Dice()};
这是您的骰子类的完整修订版
class Dice
{
private static Random random;
public Dice()
{
// create the static random generator only on the first instance
if(random == null) random = new Random();
}
public int Roll ()
{
int diceSide;
diceSide = random.Next (1, 7);
diceSide = (diceSide > 2) ? 3 : diceSide;
return diceSide;
}
}