一个类在实例化另一个类之后如何调用方法

Question

我是这个社区的新手。在发布这个问题(以及研究解决方案)之前，我已经试着了解所有规则。如果我因为无知而冒犯或违反了任何规则，我深表歉意。也请原谅我糟糕的代码，我还在学习。感谢您的理解！

编辑：我添加了更多的信息，并尝试了不同的方法来解决这个问题。我已经修改了下面的部分代码。

我正在制作一个简单的足球游戏，有一个游戏场面板和控制面板。游戏区域在GUI上显示所有球员和铲球。控制面板设置比赛的难度，启动计时器，以及四分卫的类型。我遇到了一个障碍，我有所有的代码要正确编译，但当调用GameField类上的set方法来更新分数时，它会通过我的JTextArea分数保持器更新变量，但不会更新实际分数。

我已经在GameField类中实例化了ControlPanel。我还用System.out.println()进行了测试，它表明它确实在更新变量。是否允许在类之间更新JTextArea？

GameField.java

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class GameField extends JPanel implements KeyListener {
ControlPanel cp = new ControlPanel();
// Game pieces
private JButton playerIcon = new JButton("RB");
private JButton tackleIcon1 = new JButton("LB");
private JButton tackleIcon2 = new JButton("LB");
private JButton fieldGoal = new JButton("FG");
// Player and Tackle locations
private int playerPositionX = 100;
private int playerPositionY = 500;
private int tackle1PositionX = 1200;
private int tackle1PositionY = 400;
private int tackle2PositionX = 1200;
private int tackle2PositionY = 600;
// Player variable speeds
private int playerSpeed = 20;
public GameField() {
setLayout(null);
setBackground(Color.green);
add(playerIcon);
playerIcon.setBounds(new Rectangle(getPlayerPositionX(), getPlayerPositionY(), 80, 30));
add(tackleIcon1);
tackleIcon1.setBounds(new Rectangle(getTackle1PositionX(), getTackle1PositionY(), 100, 50));
add(tackleIcon2);
tackleIcon2.setBounds(new Rectangle(getTackle2PositionX(), getTackle2PositionY(), 100, 50));
add(fieldGoal);
fieldGoal.setBounds(new Rectangle(1600, 100, 100, 800));
playerIsTackled();
setFocusable(true);
addKeyListener(this);
}
public void playerIsTackled() {
Rectangle playerRect = playerIcon.getBounds();
Rectangle tackle1Rect = tackleIcon1.getBounds();
Rectangle tackle2Rect = tackleIcon2.getBounds();
if (playerRect.intersects(tackle1Rect) || playerRect.intersects(tackle2Rect)) {
setPlayerPositionX(100);
setPlayerPositionY(500);
setTackle1PositionX(1200);
setTackle1PositionY(400);
setTackle2PositionX(1200);
setTackle2PositionY(600);
playerIcon.setBounds(getPlayerPositionX(), getPlayerPositionY(), 80, 30);
tackleIcon1.setBounds(getTackle1PositionX(), getTackle1PositionY(), 100, 50);
tackleIcon2.setBounds(getTackle2PositionX(), getTackle2PositionY(), 100, 50);
cp.setCurrentTackles(cp.getCurrentTackles() + 1);
System.out.println(cp.getCurrentTackles());
}
}
public void playerScored() {
Rectangle playerRect = playerIcon.getBounds();
Rectangle fieldGoalRect = fieldGoal.getBounds();
if (playerRect.intersects(fieldGoalRect)) {
setPlayerPositionX(100);
setPlayerPositionY(500);
setTackle1PositionX(1200);
setTackle1PositionY(400);
setTackle2PositionX(1200);
setTackle2PositionY(600);
playerIcon.setBounds(getPlayerPositionX(), getPlayerPositionY(), 80, 30);
tackleIcon1.setBounds(getTackle1PositionX(), getTackle1PositionY(), 100, 50);
tackleIcon2.setBounds(getTackle2PositionX(), getTackle2PositionY(), 100, 50);
cp.setCurrentScore(cp.getCurrentScore() + 1);
System.out.println(cp.getCurrentScore());
}
} 
public void moveToPlayer() {      
if (getTackle1PositionX() > getPlayerPositionX()) {
setTackle1PositionX(getTackle1PositionX() - 1);
} else {
setTackle1PositionX(getTackle1PositionX() + 1);
}
if (getTackle1PositionY() > getPlayerPositionY()) {
setTackle1PositionY(getTackle1PositionY() - 1);
} else {
setTackle1PositionY(getTackle1PositionY() + 1);
}
getTackleIcon1().setBounds(getTackle1PositionX(), getTackle1PositionY(), 100, 50);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
requestFocusInWindow();
playerIsTackled();
playerScored();
}
@Override
public void keyTyped(KeyEvent e) {
}
@Override
public void keyPressed(KeyEvent e) {
int k = e.getKeyCode();
if (k == e.VK_LEFT && getPlayerPositionX() > 0) {
setPlayerPositionX(getPlayerPositionX() - getPlayerSpeed());
}
if (k == e.VK_RIGHT && getPlayerPositionX() < 1703) {
setPlayerPositionX(getPlayerPositionX() + getPlayerSpeed());
}
if (k == e.VK_UP && getPlayerPositionY() > 0) {
setPlayerPositionY(getPlayerPositionY() - getPlayerSpeed());
}
if (k == e.VK_DOWN && getPlayerPositionY() < 1089) {
setPlayerPositionY(getPlayerPositionY() + getPlayerSpeed());
}
getPlayerIcon().setBounds(getPlayerPositionX(), getPlayerPositionY(), 80, 30);
}

下面是ControlPanel.java。在actionPerformed方法中，您可以看到我添加了一个getScore().setText()方法来更新分数。如果我用任何整数替换getCurrentScore()方法，它会正确地更新那里的分数。

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.Hashtable;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class ControlPanel extends JPanel implements ActionListener, ChangeListener {
private JButton start;
private JButton stop;
private JSlider speed;
private JComboBox playerList;
private Timer tim;
private int delay = 1000;
private int i = 0;
private int currentScore = 0;
private int currentTackles = 0;
private JTextArea timer = new JTextArea("Timer: " + 0, 1, 6);
private JTextArea score = new JTextArea("Field Goals: " + currentScore + "       Tackles: " + currentTackles, 1, 16);
private String[] playerStyle = {"Slow Runner", "Running Back", "All Star"};
public ControlPanel() {
super();
setBackground(Color.darkGray);
// Game controls
start = new JButton("Start");
stop = new JButton("Stop");
speed = new JSlider(JSlider.HORIZONTAL, 0, 2, 1);
playerList = new JComboBox(getPlayerStyle());
// Slider label
Hashtable labelTable = new Hashtable();
labelTable.put(new Integer(0), new JLabel("Slow"));
labelTable.put(new Integer(1), new JLabel("Normal"));
labelTable.put(new Integer(2), new JLabel("Fast"));
speed.setLabelTable(labelTable);
speed.setPaintLabels(true);
// Combo box dropdown
playerList.setSelectedIndex(1);
// Timer
tim = new Timer(getDelay(), this);
// Add methods
add(start);
add(stop);
add(timer);
add(speed);
add(score);
add(playerList);
// Event listeners
start.addActionListener(this);
stop.addActionListener(this);
speed.addChangeListener(this);
playerList.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
JComboBox cb = (JComboBox) e.getSource();
String playerChoice = (String) cb.getSelectedItem();
playerList.setSelectedItem(playerChoice);
}
});
// Set focus to false on all game controls
start.setFocusable(false);
stop.setFocusable(false);
speed.setFocusable(false);
playerList.setFocusable(false);
}
@Override
public void actionPerformed(ActionEvent event) {
Object obj = event.getSource();
if (obj == getTim()) {
setI(getI() + 1);
getTimer().setText("Timer: " + getI());
getScore().setText("Field Goals: " + getCurrentScore() + "       Tackles: " + getCurrentTackles());
}
if (obj == getStop()) {
getTim().stop();
}
if (obj == getStart()) {
getTim().start();
}
}
@Override
public void stateChanged(ChangeEvent e) {
JSlider source = (JSlider) e.getSource();
int currentSpeed = (int) source.getValue();
if (currentSpeed == 0) {
int delaySpeed = getTim().getDelay();
delaySpeed = (int) 2000;
getTim().setDelay(delaySpeed);
}
if (currentSpeed == 1) {
int delaySpeed = getTim().getDelay();
delaySpeed = (int) 1000;
getTim().setDelay(delaySpeed);
}
if (currentSpeed == 2) {
int delaySpeed = getTim().getDelay();
delaySpeed = (int) 500;
getTim().setDelay(delaySpeed);
}
}

MyJPanel.java

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyJPanel extends JPanel {
public MyJPanel() {
super();
setBackground(Color.gray);
setLayout(new BorderLayout());
ControlPanel gm = new ControlPanel();
GameField gf = new GameField();
add(gm, "North");
add(gf, "Center");
}

}

Answer 1

感谢@D.B.，我的代码可以按预期运行了。因为我只打算有两个JPanel(控制面板和游戏面板)，所以我添加了这些面板作为参数传递给彼此。在此之后，代码开始按预期工作。谢谢你把我推向正确的方向！这是一个如此简单的错误。特别感谢@DaveyDaveDave激励我更加努力！

我对我的主要JPanel对象所做的更改：

public class MyJPanel extends JPanel {
ControlPanel gm = new ControlPanel();
GameField gf = new GameField();
public MyJPanel() {
super();
setBackground(Color.gray);
setLayout(new BorderLayout());
add(gm, "North");
add(gf, "Center");
gf.setCp(gm);
gm.setGf(gf);
}
}