我的主要方法有问题，我运行它我的代码无法编译因为这个问题： ＆＃34;线程中的异常＆＃34; main＆＃34;显示java.lang.NullPointerException 在UI.ConnectFourFrame.refreshUI（ConnectFourFrame.java:96） 在UI.ConnectFourFrame。（ConnectFourFrame.java:43） 在main.main（main.java:11）＆＃34;
我试图看看问题是什么，但我无法弄明白，有人可以帮助我
package Game;
import java.util.ArrayList;
public class ConnectFourBoard {
// This constant is used to indicate the width and height, in cells,
// of the board. Since we want an 8x8 board, we'll set it to 8.
private static final int WIDTH = 7;
private static final int HEIGHT = 6;
private ConnectFourCell[][] currentPlayer;
// The current state the Othello board is defined with these two
// fields: a two-dimensional array holding the state of each cell,
// and a boolean value indicating whether it's the black player's
// turn (true) or the white player's turn (false).
private ConnectFourCell[][] cells;
private boolean isBlueTurn;
// Since the board is a model and it needs to notify views of changes,
// it will employ the standard "listener" mechanism of tracking a list
// of listeners and firing "events" (by calling methods on those
// listeners) when things change.
private ArrayList<ConnectFourListener> listeners;
public ConnectFourBoard()
{
// Arrays, in Java, are objects, which means that variables of
// array types (like cells, which has type OthelloCell[][]) are
// really references that say where an array lives. By default,
// references point to null. So we'll need to create an actual
// two-dimensional array for "cells" to point to.
cells = new ConnectFourCell[WIDTH][HEIGHT];
listeners = new ArrayList<ConnectFourListener>();
reset();
}
public void reset(){
for (int i = 0; i<WIDTH ; i++){
for (int j = 0; j<HEIGHT; j++){
cells[i][j] = ConnectFourCell.NONE;
}
}
isBlueTurn = true;
}
public void addConnectFourListener(ConnectFourListener listener)
{
listeners.add(listener);
}
public void removeConnectFourListener(ConnectFourListener listener)
{
if (listeners.contains(listener))
{
listeners.remove(listener);
}
}
// These are fairly standard "fire event" methods that we've been building
// all quarter, one corresponding to each method in the listener interface.
private void fireBoardChanged()
{
for (ConnectFourListener listener : listeners)
{
listener.boardChanged();
}
}
private void fireGameOver()
{
for (ConnectFourListener listener : listeners)
{
listener.gameOver();
}
}
// isBlackTurn() returns true if it's the black player's turn, and false
// if it's the white player's turn.
public boolean isBlueTurn()
{
return isBlueTurn;
}
public int getWidth()
{
return WIDTH;
}
public int getHeight(){
return HEIGHT;
}
// getBlackScore() calculates the score for the black player.
public int getBlackScore()
{
return getScore(ConnectFourCell.BLUE);
}
// getWhiteScore() calculates the score for the white player.
public int getWhiteScore()
{
return getScore(ConnectFourCell.RED);
}
// getScore() runs through all the cells on the board and counts the
// number of cells that have a particular value (e.g., BLACK or WHITE).
// This method uses the naive approach of counting them each time
// it's called; it might be better to keep track of this score as we
// go, updating it as tiles are added and flipped.
private int getScore(ConnectFourCell cellValue)
{
int score = 0;
for (int i = 0; i < WIDTH; i++)
{
for (int j = 0; j < HEIGHT; j++)
{
if (cells[i][j] == cellValue)
{
score++;
}
}
}
return score;
}
// getWhiteScore() calculates the score for the white player.
public int getRedScore()
{
return getScore(ConnectFourCell.RED);
}
public int getBlueScore() {
// TODO Auto-generated method stub
return getScore(ConnectFourCell.BLUE);
}
public ConnectFourCell getCell(int x, int y)
{
if (!isValidCell(x, y))
{
throw new IllegalArgumentException(
"(" + x + ", " + y + ") is not a valid cell");
}
return cells[x][y];
}
/**
* The drop method.
*
* Drop a checker into the specified HEIGHT,
* and return the WIDTH that the checker lands on.
*/
int drop(int HEIGHT) {
if (hasWon()) {
return -1;
}
for ( ; WIDTH<6 && HEIGHT != 0; WIDTH++) { };
if (WIDTH==6) {
// if the WIDTH is 6, it went through all 6 WIDTHs
// of the cells, and couldn't find an empty one.
// Therefore, return false to indicate that this
// drop operation failed.
return -1;
}
// fill the WIDTH of that HEIGHT with a checker.
cells[HEIGHT][WIDTH] = currentPlayer[HEIGHT][WIDTH];
// alternate the players
//currentPlayer = (currentPlayer%2)+1;
return WIDTH;
}
/**
* The toString method
*
* Returns a String representation of this
* Connect Four (TM) game.
*/
public String toString() {
String returnString = "";
for (int WIDTH=5; WIDTH>=0; WIDTH--) {
for (int HEIGHT=0; HEIGHT<7; HEIGHT++) {
returnString = returnString + cells[HEIGHT][WIDTH];
}
returnString = returnString + "\n";
}
return returnString;
}
/**
* The hasWon method.
*
* This method returns true if one of the
* players has won the game.
*/
public boolean hasWon() {
boolean status = false;
// check for a horizontal win
for (int WIDTH=0; WIDTH<6; WIDTH++) {
for (int HEIGHT=0; HEIGHT<4; HEIGHT++) {
if (!(cells[HEIGHT][WIDTH] == ConnectFourCell.NONE) &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+1][WIDTH] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+2][WIDTH] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+3][WIDTH]) {
status = true;
}
}
}
// check for a vertical win
for (int WIDTH=0; WIDTH<3; WIDTH++) {
for (int HEIGHT=0; HEIGHT<7; HEIGHT++) {
if (!(cells[HEIGHT][WIDTH] == ConnectFourCell.NONE) &&
cells[HEIGHT][WIDTH] == cells[HEIGHT][WIDTH+1] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT][WIDTH+2] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT][WIDTH+3]) {
status = true;
}
}
}
// check for a diagonal win (positive slope)
for (int WIDTH=0; WIDTH<3; WIDTH++) {
for (int HEIGHT=0; HEIGHT<4; HEIGHT++) {
if (!(cells[HEIGHT][WIDTH] == ConnectFourCell.NONE) &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+1][WIDTH+1] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+2][WIDTH+2] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+3][WIDTH+3]) {
status = true;
}
}
}
// check for a diagonal win (negative slope)
for (int WIDTH=3; WIDTH<6; WIDTH++) {
for (int HEIGHT=0; HEIGHT<4; HEIGHT++) {
if (!(cells[HEIGHT][WIDTH] == ConnectFourCell.NONE) &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+1][WIDTH-1] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+2][WIDTH-2] &&
cells[HEIGHT][WIDTH] == cells[HEIGHT+3][WIDTH-3]) {
status = true;
}
}
}
return status;
}
private boolean isValidCell(int x, int y)
{
return x >= 0 && x < WIDTH
&& x>= 0 && x<HEIGHT
&& y >= 0 && y < WIDTH
&& y>= 0 && y<HEIGHT;
}
}
package UI;
import java.awt.*;
import javax.swing.*;
import UI.ConnectFourBoardPanel;
import Game.ConnectFourBoard;
import Game.ConnectFourListener;
public class ConnectFourFrame extends JFrame implements ConnectFourListener {
// Variables
private ConnectFourBoard board;
private JLabel scoreLabel;
private ConnectFourBoardPanel boardPanel;
private JLabel statusLabel;
public ConnectFourFrame()
{
// The frame builds its own model.
ConnectFourBoard board = new ConnectFourBoard();
// We want the frame to receive notifications from the board as its
// state changes.
System.out.println(this);
board.addConnectFourListener(this);
setTitle("Informatics 45 Spring 2011: ConnectFour Game");
setSize(700, 700);
setResizable(true);
setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
getContentPane().setBackground(Color.BLACK);
buildUI();
refreshUI();
}
private void buildUI()
{
GridBagLayout layout = new GridBagLayout();
getContentPane().setLayout(layout);
Font labelFont = new Font("SansSerif", Font.BOLD, 18);
scoreLabel = new JLabel();
scoreLabel.setForeground(Color.WHITE);
scoreLabel.setFont(labelFont);
layout.setConstraints(
scoreLabel,
new GridBagConstraints(
0, 0, 1, 1, 1.0, 0.0,
GridBagConstraints.CENTER,
GridBagConstraints.NONE,
new Insets(10, 10, 10, 10), 0, 0));
getContentPane().add(scoreLabel);
boardPanel = new ConnectFourBoardPanel(board);
layout.setConstraints(
boardPanel,
new GridBagConstraints(
0, 1, 1, 1, 1.0, 1.0,
GridBagConstraints.CENTER,
GridBagConstraints.BOTH,
new Insets(10, 10, 10, 10), 0, 0));
getContentPane().add(boardPanel);
statusLabel = new JLabel();
statusLabel.setForeground(Color.WHITE);
statusLabel.setFont(labelFont);
layout.setConstraints(
statusLabel,
new GridBagConstraints(
0, 2, 1, 1, 1.0, 0.0,
GridBagConstraints.CENTER,
GridBagConstraints.NONE,
new Insets(10, 10, 10, 10), 0, 0));
getContentPane().add(statusLabel);
}
private void refreshUI()
{
// Refreshing the UI means to change the text in each of the
// two labels (the score and the status) and also to ask the
// board to repaint itself.
scoreLabel.setText(
"Blue: " + board.getBlueScore() +
" Red: " + board.getRedScore());
statusLabel.setText(
(board.isBlueTurn() ? "Blue's" : "Red's")
+ " turn");
boardPanel.repaint();
}
// These are the ConnectFourBoardListener event-handling methods.
public void boardChanged()
{
// When the board changes, we'll refresh the entire UI. (There
// are times when this approach is too inefficient, but it will
// work fine for our relatively simple UI.)
refreshUI();
}
public void gameOver()
{
// When the game is over, we'll pop up a message box showing the final
// score, then, after the user dismisses the message box, dispose of
// this window and end the program.
JOptionPane.showMessageDialog(
this,
"Game over!\nFinal score: " + scoreLabel.getText(),
"Game Over",
JOptionPane.INFORMATION_MESSAGE);
dispose();
}
}
答案 0 :(得分：2)
初始化本地var而不是你的成员var
ConnectFourBoard board = new ConnectFourBoard();
将该行更改为：
board = new ConnectFourBoard();
答案 1 :(得分：0)
查看完整堆栈跟踪会很有帮助，但是{{1and1}}似乎是返回整数，而您尝试使用getBlueScore()设置它将需要一个字符串。