Question

我在代码的这一部分出现PacmanGame.exe错误时发生'System.NullReferenceException'：

if (cells[yPosition + 1, xPosition].CellType == 'o' 
                    || cells[yPosition + 1, xPosition].CellType == '.'
                    || cells[yPosition + 1, xPosition].CellType == '!')

    public partial class Form1 : Form
    {
        const int cellSize = 20; //cell dimension in pixels
        // The two-dimensional array of Cells that will make up the maze 
        private Cell[,] cells;
        // the width of the map in tiles (NOT pixels)
        private int mapWidth;
        // the height of the map in tiles (NOT pixels)
        private int mapHeight;



        private Image[] pacmanImage = new Image[4];
        public int currentMouthPosition { get; set; }
        private Image[] ghostImage = new Image[2];
        private Random rnd = new Random();
        private int currentEyePosition { get; set; } //= 0;
        private int score = 0;
        private int lives = 3;

       // private PacmanMove pacman;


        private int xPositiong = 520;//  initial xPosition for the ghost

        private int yPositiong = 200;//  initial yPosition for the ghost

        private int xpos = 420;//  initial xPosition for the Pacman

        private int ypos = 260;//  initial yPosition for the Pacman


        public int pacmanisfaceing = 0;



 // timer1 is for pacman

        public void timer1_Tick(object sender, EventArgs e)
        {

            int xPosition = xpos / 20;
            int yPosition = ypos / 20;
           currentMouthPosition += 1;
            if (currentMouthPosition > 3) currentMouthPosition = 0;


            if (xPosition < 0) xPosition = this.Width;
            else if (xPosition > this.Width) xPosition = 0;

            if (yPosition < 0) yPosition = this.Height;
            else if (yPosition > this.Height) yPosition = 0;


            // if statement for detecting the walls so pacman wont go through them
            if (pacmanisfaceing == 0) // used to detect walls when pacman is facing down
            {
                if (cells[yPosition + 1, xPosition].CellType == 'o' 
                    || cells[yPosition + 1, xPosition].CellType == '.'
                    || cells[yPosition + 1, xPosition].CellType == '!')
                {

                  yPosition += 10;
                   // CheckCollision(); // checks if pacman has had a collision with a ghost

                    if (cells[yPosition + 1, xPosition].CellType == '.'
                        && (cells[yPosition, xPosition].IsVisible == true)) //if statement used detect a pill and if one is visible
                    {                                                                                                    // it will add up the number of pills lifted

                        cells[yPosition, xPosition].IsVisible = false; // this is the code for adding up the score of the pills
                        score += 10; // adds on 10 everytime a pill is lifted
                        ScoreInfoEventArgs currentScore = new ScoreInfoEventArgs(score);
                        OnScoreChanged(currentScore);
                    }

                    // if statement for detecting the power pills and adding on extra points
                    if (cells[yPosition + 1, xPosition].CellType == '!' && (cells[yPosition, xPosition].IsVisible == true))
                    {
                        cells[yPosition, xPosition].IsVisible = false;
                        score += 50; // adds on 50 points when a power pill is lifted
                        ScoreInfoEventArgs currentScore = new ScoreInfoEventArgs(score);
                        OnScoreChanged(currentScore);
                        //SoundPlayer myPlayerMove = new SoundPlayer("..\\..\\Sounds\\pacman_eatfruit.wav"); // plays the eat fruit tune when a power pill is lifted
                       // myPlayerMove.Play();
                    }

                }

            }

Answer 1

在该特定行中只有两件事可能为空

(cells[yPosition + 1, xPosition].CellType == 'o' || cells[yPosition + 1, xPosition].CellType == '.' || cells[yPosition + 1, xPosition].CellType == '!')

细胞
细胞的数组元素[yPosition + 1，xPosition]

如果 cells 为null，那么这是一个简单的修复 - 只是意味着单元格引用的对象尚未实例化。如果数组元素为null，则单元格索引的逻辑或填充单元格数组的逻辑是错误的。

PacmanGame.exe中出现未处理的“System.NullReferenceException”类型异常

1 个答案: