我正在为大学作业创建一个游戏，并试图在JFrame中按下按钮时在我的GameEnviroment类中设置一个变量，但是它踢出了以下错误。我通过在类的变量声明中声明该类的新实例找到了一种解决方法，但是我需要在多个JFrame之间不断传递相同的实例。下面是JFrame代码和我尝试创建/传递实例的类。
当我尝试设置实例游戏的游戏天数变量时，错误似乎在第52行中。我曾尝试过其他吸气剂和吸气剂，但似乎都不起作用
这是我的JUnit窗口：
package displays;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JComboBox;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JSlider;
import main.GameEnviroment;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class SelectDays {
private JFrame frmHowManyDay;
public GameEnviroment game;
public int numInt;
/**
* Launch the application.
*/
/**
* Create the application.
*/
public SelectDays() {
GameEnviroment game = new GameEnviroment();
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frmHowManyDay = new JFrame();
frmHowManyDay.setTitle("How Many Day Would You Like Your Adventure To Last?");
frmHowManyDay.setBounds(100, 100, 630, 192);
frmHowManyDay.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frmHowManyDay.getContentPane().setLayout(null);
final JComboBox comboBox = new JComboBox();
comboBox.setModel(new DefaultComboBoxModel(new String[] {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10"}));
comboBox.setBounds(259, 12, 96, 64);
frmHowManyDay.getContentPane().add(comboBox);
JButton btnNewButton = new JButton("OKAY");
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
int number = Integer.parseInt((String) comboBox.getSelectedItem());
game.setGameDays(number);
System.out.println(game.getGameDays());
ShipAndCrew shipAndCrew = new ShipAndCrew(game);
shipAndCrew.getFrmSelectCrew().setVisible(true);
//move to the next window
}
});
btnNewButton.setBounds(250, 106, 120, 25);
frmHowManyDay.getContentPane().add(btnNewButton);
}
public JFrame getFrmHowManyDay() {
return frmHowManyDay;
}
public void setFrmHowManyDay(JFrame frmHowManyDay) {
this.frmHowManyDay = frmHowManyDay;
}
public GameEnviroment getGame() {
return game;
}
public void setGame(GameEnviroment game) {
this.game = game;
}
}
这是我的GameEnviroment类：（删除了一些方法，因为它们不重要）
public class GameEnviroment {
int gameDays = 0;
int shipPieces;
int shipPiecesFound = 0;
int planetCount;
int crewMemeberCount = 0;
boolean allFound = false;
SpaceShip spaceShip;
Planet currentPlanet;
public ArrayList<Planet> planets = new ArrayList<Planet>();
public GameEnviroment() {
this.gameDays = 0;
}
//AAAAEG
/*
public static void main(String args[]) {
GameEnviroment game = new GameEnviroment();
//open loading screen, then open
//select days
System.out.println("Welcome to the game bby ;)");
game.init(game);
System.out.println("Welcome travellers aboard the ship " + game.spaceShip.getName() + " with crew");
System.out.println(game.spaceShip.getCrewList());
System.out.println("You will have " + game.gameDays + " days to explore the system with " + game.planetCount + " Planets");
System.out.println("Here is your map");
System.out.println(game.planets);
game.currentPlanet = game.planets.get(ThreadLocalRandom.current().nextInt(0, game.planets.size()));
game.planets.remove(game.currentPlanet);
for(int i = 1; i <= game.gameDays; i++) {
//now we play the game
System.out.println("It is day " + i + " what would you like to do first?");
game.allFound = game.gameday(game);
if(game.allFound) {
i = game.gameDays;
}
//we need random events to happen during the night??? 'game.gameNight()?
}
}
*/
public void init(GameEnviroment game) {
//this is for selecting charecters and lenght
shipPieces = Math.round((gameDays*2)/3);
//here we need to create a new spaceship object
//need to init planets
planetCount = gameDays;
for(int j = 0; j < planetCount; j++) {
//now we generate the correct amount of planets
//name, part present, int foodDropMax, int healthDropMax, int moneyDropMax
if(j < game.shipPieces) {
Planet planet = new Planet("name", true, randomPcChance(70), randomPcChance(50), randomPcChance(60));
planets.add(planet);
}else {
Planet planet = new Planet("name", false, randomPcChance(70), randomPcChance(50), randomPcChance(60));
planets.add(planet);
}
}
}
public boolean gameday(GameEnviroment game) {
//returns if all the pieces have been found
//each gameday this loop is called
//goes to a random planet when the player wants to and is able to, removes it from the list of planets
//check if all pieces have been found
String whatsHappend = checkRandomEvents(game);
System.out.println(whatsHappend);
Scanner scanner = new Scanner(System.in);
String tempCrewName = "c";
while(tempCrewName.equals("x") != true) {
System.out.println("What Charecter would you like to use?");
tempCrewName = scanner.next();
if(tempCrewName.equals("x") != true) {
charActions(tempCrewName, game);
}
if(game.shipPieces == game.shipPiecesFound) {
System.out.println("You found all the bits! congrats");
return true;
}
}
for(CrewMember crewMember: game.spaceShip.crewList) {
crewMember.setActionsLeft(2);
//how are we doing the degrading of health and shit
crewMember.setTiredness(crewMember.getTireddeg() * 30);
crewMember.setHunger(crewMember.getHungerdeg() * 30);
//reset all actions left for chars and check health/hunger ect
}
return false;
}
public int getGameDays() {
return gameDays;
}
public void setGameDays(int gameDays) {
this.gameDays = gameDays;
}
public int getShipPieces() {
return shipPieces;
}
public void setShipPieces(int shipPieces) {
this.shipPieces = shipPieces;
}
public int getShipPiecesFound() {
return shipPiecesFound;
}
public void setShipPiecesFound(int shipPiecesFound) {
this.shipPiecesFound = shipPiecesFound;
}
public int getPlanetCount() {
return planetCount;
}
public void setPlanetCount(int planetCount) {
this.planetCount = planetCount;
}
}
我希望它设置gameDays的变量并继续，但是显示此错误消息：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at displays.SelectDays$1.actionPerformed(SelectDays.java:52)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:270)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6589)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
at java.desktop/java.awt.Component.processEvent(Component.java:6354)
at java.desktop/java.awt.Container.processEvent(Container.java:2261)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4966)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2319)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4798)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4914)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4543)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4484)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2305)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2772)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4798)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
at java.desktop/java.awt.EventQueue.access$600(EventQueue.java:97)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:97)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
答案 0 :(得分：1)
您不是在构造函数中初始化类成员，而是声明和初始化新的局部变量
GameEnviroment game = new GameEnviroment();
像这样初始化它
game = new GameEnviroment();