我目前正在为我的c＃课练习。我在某个特定部分遇到了一些麻烦，非常感谢你的帮助。
我正在进行一项练习，其中我们获得了一个不完整的项目文件。
该项目有多个类，该类用于控制放置在电路板上的方块。
namespace HareAndTortoise {
public partial class SquareControl : PictureBox {
public const int SQUARE_SIZE = 100;
private Square square; // A reference to the corresponding square object
private BindingList<Player> players; // References the players in the overall game.
private bool[] containsPlayers = new bool[6];//HareAndTortoiseGame.MAX_PLAYERS];
public bool[] ContainsPlayers {
get {
return containsPlayers;
}
set {
containsPlayers = value;
}
}
// Font and brush for displaying text inside the square.
private Font textFont = new Font("Microsoft Sans Serif", 8);
private Brush textBrush = Brushes.White;
public SquareControl(Square square, BindingList<Player> players) {
this.square = square;
this.players = players;
// Set GUI properties of the whole square.
Size = new Size(SQUARE_SIZE, SQUARE_SIZE);
Margin = new Padding(0); // No spacing around the cell. (Default is 3 pixels.)
Dock = DockStyle.Fill;
BorderStyle = BorderStyle.FixedSingle;
BackColor = Color.CornflowerBlue;
SetImageWhenNeeded();
}
private void SetImageWhenNeeded()
{
if (square is Square.Win_Square)
{
LoadImageFromFile("Win.png");
textBrush = Brushes.Black;
}
else if (square is Square.Lose_Square)
{
LoadImageFromFile("Lose.png");
textBrush = Brushes.Red;
}
else if (square is Square.Chance_Square)
{
LoadImageFromFile("monster-green.png");
}
else if (square.Name == "Finish")
{
LoadImageFromFile("checkered-flag.png");
}
else
{
// No image needed.
}
}
private void LoadImageFromFile(string fileName) {
Image image = Image.FromFile(@"Images\" + fileName);
Image = image;
SizeMode = PictureBoxSizeMode.StretchImage; // Zoom is also ok.
}
protected override void OnPaint(PaintEventArgs e) {
// Due to a limitation in WinForms, don't use base.OnPaint(e) here.
if (Image != null)
e.Graphics.DrawImage(Image, e.ClipRectangle);
string name = square.Name;
// Create rectangle for drawing.
float textWidth = textFont.Size * name.Length;
float textHeight = textFont.Height;
float textX = e.ClipRectangle.Right - textWidth;
float textY = e.ClipRectangle.Bottom - textHeight;
RectangleF drawRect = new RectangleF(textX, textY, textWidth, textHeight);
// When debugging this method, show the drawing-rectangle on the screen.
//Pen blackPen = new Pen(Color.Black);
//e.Graphics.DrawRectangle(blackPen, textX, textY, textWidth, textHeight);
// Set format of string.
StringFormat drawFormat = new StringFormat();
drawFormat.Alignment = StringAlignment.Far; // Right-aligned.
// Draw string to screen.
e.Graphics.DrawString(name, textFont, textBrush, drawRect, drawFormat);
// Draw player tokens (when any players are on this square).
const int PLAYER_TOKENS_PER_ROW = 3;
const int PLAYER_TOKEN_SIZE = 30; // pixels.
const int PLAYER_TOKEN_SPACING = (SQUARE_SIZE - (PLAYER_TOKEN_SIZE * PLAYER_TOKENS_PER_ROW)) / (PLAYER_TOKENS_PER_ROW - 1);
for (int i = 0; i < containsPlayers.Length; i++) {
if (containsPlayers[i]) {
int xPosition = i % PLAYER_TOKENS_PER_ROW;
int yPosition = i / PLAYER_TOKENS_PER_ROW;
int xPixels = xPosition * (PLAYER_TOKEN_SIZE + PLAYER_TOKEN_SPACING);
int yPixels = yPosition * (PLAYER_TOKEN_SIZE + PLAYER_TOKEN_SPACING);
Brush playerTokenColour = players[i].PlayerTokenColour;
e.Graphics.FillEllipse(playerTokenColour, xPixels, yPixels, PLAYER_TOKEN_SIZE, PLAYER_TOKEN_SIZE);
}
}//endfor
}
}
}
该计划在以下地点绊倒：
else if (square.Name == "Finish")
{
LoadImageFromFile("checkered-flag.png");
}
我知道这是因为square.name，但是通过代码，我无法理解为什么square.Name不可识别。
使用此方法从另一个类传递Square
private void SetUpGuiGameBoard()
{
for (int i = 0; i <= 55; i++)
{
Square q = Board.GetGameBoardSquare(i);
SquareControl sq = new SquareControl(q, null);
int coloumn;
int row;
if (i == 0)
{
BackColor = Color.BurlyWood;
}
if (i == 55)
{
BackColor = Color.BurlyWood;
}
MapSquareNumToTablePanel(i, out coloumn, out row);
tableLayoutPanel1.Controls.Add(sq, coloumn, row);
}
和Squares在这个类中创建
private static Square[] gameBoard = new Square[56];
static public void SetUpBoard()
{
for (int i = 1; i == 55; i++)
{
gameBoard[i] = new Square("Ordinary Square", i);
}
gameBoard[0] = new Square("Start", 0);
gameBoard[4] = new Square.Lose_Square("Lose Square", 4);
gameBoard[5] = new Square.Chance_Square("Chance Square", 5);
gameBoard[9] = new Square.Win_Square("Win Square", 9);
gameBoard[11] = new Square.Chance_Square("Chance Square", 11);
gameBoard[14] = new Square.Lose_Square("Lose Square", 14);
gameBoard[17] = new Square.Chance_Square("Chance Square", 17);
gameBoard[19] = new Square.Win_Square("Win Square", 19);
gameBoard[24] = new Square.Lose_Square("Lose Square", 24);
gameBoard[29] = new Square.Win_Square("Win Square", 29);
gameBoard[34] = new Square.Lose_Square("Lose Square", 34);
gameBoard[35] = new Square.Chance_Square("Chance Square", 35);
gameBoard[39] = new Square.Win_Square("Win Square", 39);
gameBoard[44] = new Square.Lose_Square("Lose Square", 44);
gameBoard[47] = new Square.Chance_Square("Chance Square", 47);
gameBoard[49] = new Square.Win_Square("Win Square", 49);
gameBoard[53] = new Square.Chance_Square("Chance Square", 53);
gameBoard[55] = new Square("Finish", 56);
}
public static Square GetGameBoardSquare(int n)
{
return gameBoard[n];
}
public static Square StartSquare()
{
return gameBoard[0];
}
public static Square NextSquare(int n)
{
return gameBoard[(n+1)];
}
}
答案 0 :(得分：0)
已经提供的答案是防止任何空引用异常的最佳方法。为了进一步说明，我建议您在调试器到达SquareControl构造函数时检查调用堆栈。此时，您应该检查传入的Square对象为何为“NULL”。这将引导您找到问题的根本原因。希望这会有所帮助。