单击事件 - 从另一个 class 访问布尔变量

Question

遇到一个需要从另一个 class.

获取 boolean 变量的问题

我有以下 for-loop、boolean 和 if-else 语句

import java.awt.*;
import javax.swing.*;
import java.awt.Color.*;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import java.util.Random;

public class Checkers extends JFrame 
{
    Random random = new Random();
    private final int ROWS = 2;
    private final int COLS = 5;
    private final int GAP = 2;
    private final int NUM = ROWS * COLS;
    private int i;
    private int score;
    private JPanel pane = new JPanel(new GridLayout(ROWS,COLS, GAP,GAP));
    private JPanel pane2 = new JPanel();
    private JPanel pane3 = new JPanel();

    private JButton btn1 = new JButton("Play A Game");
    private JButton btn2 = new JButton("Exit");

    private JButton btn3 = new JButton("Easy");
    private JButton btn4 = new JButton("Intermediate");
    private JButton btn5 = new JButton("Difficult");
    private JLabel lbl1 = new JLabel ("score: " + score);
    private JLabel gameLost = new JLabel("You lose! You got: " + score + " points");

    private JButton btnRestart = new JButton("Restart");

    private MyPanel [] panel = new MyPanel[NUM];
    private Color col1 = Color.RED;
    private Color col2 = Color.WHITE;
    private Color col3 = Color.GREEN;
    private Color tempColor;
    private boolean isPanelDisabled;

    //Starts the checkers GUI, calling the constructor below this.

    public static void main(String[] args){
        new Checkers();
    }

    //Sets the dimensions of the GUI, visibility, background color and 
    //contents via the setBoard(); 

    public Checkers()
    {
        super("Checkers");
        setSize(600,600);
        setVisible(true);
        setBackground(Color.BLACK);
        setBoard();
    }

    //Makes the grid, contains a conditional boolean, adds the panels to grid based on i value.
    //sets Colours accordingly

    public void setBoard()


    {

        boolean isPanelDisabled = false;
        for (int i = 0; i < panel.length; i++) {
            panel[i] = new MyPanel(this);
            pane.add(panel[i]);

            if (i % COLS == 0) {
                tempColor = col1;
            }
            if (i == 9 || i <8) {
                panel[i].setBackground(col1);

            }
            if(i == 8){
                isPanelDisabled = true;
                panel[i].setBackground(col3);
            }

        }

        //pane background colour and the size of this pane.

        pane.setBackground(Color.BLACK);
        pane.setPreferredSize(new Dimension(300,300));

        //pane background colour and size of this pane.

        pane2.setBackground(Color.white);
        pane2.setPreferredSize(new Dimension(300,300));

        //directions on the board where these panes appear.

        add(pane, BorderLayout.WEST);
        add(pane2, BorderLayout.EAST);
        pane2.add(lbl1);
        pane2.add(btnRestart);
        btnRestart.addActionListener( e -> restartBoard());
        pane2.setLayout(new BoxLayout(pane2, BoxLayout.PAGE_AXIS));

    }

    //increments the score for the user based on current points.

    public void incrementScore(){
        if (score != 5){

            score++;
            lbl1.setText("Score: " + Integer.toString(score));
        }
        else if(score == 5){

            lbl1.setText("Congratulations!, you've won!, your score is:" + score);
        }

    }
}

和这个 mouseClicked 事件

 import java.awt.Color;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.*;  
import java.awt.event.*;  
import javax.swing.JPanel;


public class MyPanel extends JPanel implements MouseListener, ActionListener {
    private final Checkers checkers;
    private boolean isPanelDisabled;

    //MyPanel Constructor that initiates a instance of checkers.

    public MyPanel(Checkers checkers) {
        this.checkers = checkers;
        addMouseListener(this);

    }

    @Override
    public void actionPerformed(ActionEvent e){

    }
    // Sets the panel colours according to their int number and the boolean condiiton.
    @Override
    public void mouseClicked(MouseEvent e) {
        if (isPanelDisabled == true){ 

            setBackground(Color.CYAN);
        }
        else{
            setBackground(Color.BLACK);
            checkers.incrementScore();
        }

    }

我的预期结果应该是，如果用户单击该网格中的第 8 个面板，则该面板的颜色在按下时将是青色而不是黑色，但它无法访问布尔变量？我哪里错了？

Answer 1

你的问题涉及到不同 class 对象之间的通信，有几种方法可以做到这一点，但最基本的是调用一个 class 中对象的方法给另一个.

首先让我们设置问题，...我创建了 classes 称为 MyPanel2 和 Checkers2，以将它们与您的区分开来。

假设在 MyPanel2 中我们有一个 Checkers2 字段和一个名为 selected 且设置为 false 的布尔字段：

private Checkers2 checkers;
private boolean selected = false;

以及适当的布尔值 getter 和 setter:

public void setSelected(boolean selected) {
    this.selected = selected;
}

public boolean isSelected() {
    return selected;
}

然后说在 Checkers2 class 中，您有 10 个 MyPanel2 实例保存在一个数组中，并且您希望用户能够 "select" 个 class 实例，但只允许选择其中的 7 个，并假设您想要使用您当前正在使用的设置，您可以提供主要 class、一个方法 public boolean isPanelDisabled()，并让MyPanel2 class 调用此方法来确定是否允许选择。所以在 MyPanel2 中你可以有一个 MouseListener 像这样：

@Override
public void mousePressed(MouseEvent e) {
    if (selected) {
        return;
    }

    // call the Checkers2 boolean method to check
    if (checkers.isPanelDisabled()) {
        setBackground(DISABLED_COLOR);
    } else {
        setBackground(SELECTED_COLOR);
        setSelected(true);
    }
}

在 Checkers2 .isPanelDisabled() 方法中，您将遍历 MyPanel2 实例的数组以查看已选择了多少，这样的方法可能有效：

public boolean isPanelDisabled() {
    int count = 0;
    for (MyPanel2 panel2 : myPanels) {
        if (panel2.isSelected()) {
            count++;
        }
    }
    return count >= MAX_COUNT;
}

整个 MCVE 可测试代码可能如下所示：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Checkers2 extends JFrame {
    private static final int MAX_COUNT = 7;
    private final int ROWS = 2;
    private final int COLS = 5;
    private final int GAP = 2;
    private final int NUM = ROWS * COLS;
    private MyPanel2[] myPanels = new MyPanel2[NUM];

    public Checkers2() {
        super("Checkers");
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        JPanel gridPanel = new JPanel(new GridLayout(ROWS, COLS, 1, 1));
        gridPanel.setBackground(Color.BLACK);
        gridPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        for (int i = 0; i < myPanels.length; i++) {
            MyPanel2 myPanel = new MyPanel2(this);
            gridPanel.add(myPanel);
            myPanels[i] = myPanel;
        }

        JButton resetButton = new JButton("Reset");
        resetButton.setMnemonic(KeyEvent.VK_R);
        resetButton.addActionListener(evt -> {
            for (MyPanel2 myPanel2 : myPanels) {
                myPanel2.reset();
            }
        });
        JButton exitButton = new JButton("Exit");
        exitButton.setMnemonic(KeyEvent.VK_X);
        exitButton.addActionListener(evt -> System.exit(0));

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(resetButton);

        add(gridPanel);
        add(buttonPanel, BorderLayout.PAGE_END);

        pack();
        setLocationRelativeTo(null);
    }

    public boolean isPanelDisabled() {
        int count = 0;
        for (MyPanel2 panel2 : myPanels) {
            if (panel2.isSelected()) {
                count++;
            }
        }
        return count >= MAX_COUNT;
    }


    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            new Checkers2().setVisible(true);
        });
    }

}

class MyPanel2 extends JPanel {
    private static final int PREF_W = 200;
    private static final int PREF_H = PREF_W;
    private static final int GR = 240;
    public static final Color BASE_COLOR = new Color(GR, GR, GR);
    public static final Color DISABLED_COLOR = Color.CYAN;
    public static final Color SELECTED_COLOR = Color.BLACK;
    private Checkers2 checkers;
    private boolean selected = false;

    public MyPanel2(Checkers2 checkers) {
        setBackground(BASE_COLOR);
        this.checkers = checkers;
        setPreferredSize(new Dimension(PREF_W, PREF_H));
        addMouseListener(new MyMouse());
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
    }

    public boolean isSelected() {
        return selected;
    }

    public void reset() {
        setBackground(BASE_COLOR);
        setSelected(false);
    }

    private class MyMouse extends MouseAdapter {
        @Override
        public void mousePressed(MouseEvent e) {
            if (selected) {
                return;
            }
            if (checkers.isPanelDisabled()) {
                setBackground(DISABLED_COLOR);
            } else {
                setBackground(SELECTED_COLOR);
                setSelected(true);
            }
        }
    }
}

另一个选项是把MyPanel的所有逻辑out放到主程序中，比如：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class Checkers3 extends JPanel {
    private static final int MAX_COUNT = 7;
    private final int ROWS = 2;
    private final int COLS = 5;
    private final int GAP = 2;
    private final int NUM = ROWS * COLS;
    private MyPanel3[] myPanels = new MyPanel3[NUM];

    public Checkers3() {
        JPanel gridPanel = new JPanel(new GridLayout(ROWS, COLS, 1, 1));
        gridPanel.setBackground(Color.BLACK);
        gridPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK));
        MyMouse myMouse = new MyMouse();
        for (int i = 0; i < myPanels.length; i++) {
            MyPanel3 myPanel = new MyPanel3();
            myPanel.addMouseListener(myMouse);
            gridPanel.add(myPanel);
            myPanels[i] = myPanel;
        }

        JButton resetButton = new JButton("Reset");
        resetButton.setMnemonic(KeyEvent.VK_R);
        resetButton.addActionListener(evt -> {
            for (MyPanel3 myPanel : myPanels) {
                myPanel.reset();
            }
        });
        JButton exitButton = new JButton("Exit");
        exitButton.setMnemonic(KeyEvent.VK_X);
        exitButton.addActionListener(evt -> System.exit(0));

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(resetButton);

        setLayout(new BorderLayout());
        add(gridPanel);
        add(buttonPanel, BorderLayout.PAGE_END);
    }

    public boolean isPanelDisabled() {
        int count = 0;
        for (MyPanel3 panel : myPanels) {
            if (panel.isSelected()) {
                count++;
            }
        }
        return count >= MAX_COUNT;
    }

    private class MyMouse extends MouseAdapter {
        @Override
        public void mousePressed(MouseEvent e) {
            MyPanel3 myPanel = (MyPanel3) e.getSource();
            if (myPanel.isSelected()) {
                return; // it's already selected
            } else if (isPanelDisabled()) {
                myPanel.setSelected(false);
            } else {
                myPanel.setSelected(true);
            }
        }
    }

    private static void createAndShowGui() {
        Checkers3 mainPanel = new Checkers3();

        JFrame frame = new JFrame("Checkers");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

@SuppressWarnings("serial")
class MyPanel3 extends JPanel {
    private static final int PREF_W = 200;
    private static final int PREF_H = PREF_W;
    private static final int GR = 240;
    public static final Color BASE_COLOR = new Color(GR, GR, GR);
    public static final Color DISABLED_COLOR = Color.CYAN;
    public static final Color SELECTED_COLOR = Color.BLACK;
    private boolean selected = false;

    public MyPanel3() {
        setBackground(BASE_COLOR);
        setPreferredSize(new Dimension(PREF_W, PREF_H));
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
        Color background = selected ? SELECTED_COLOR : DISABLED_COLOR;
        setBackground(background);
    }

    public boolean isSelected() {
        return selected;
    }

    public void reset() {
        setSelected(false);
        setBackground(BASE_COLOR);
    }
}

但是 BEST 选项是将所有逻辑放在一个单独的模型 class（或 classes）中，并使 GUI 尽可能简单.

单击事件 - 从另一个 class 访问布尔变量

Click Event - Accessing a boolean variable from another class

java

swing

boolean

jpanel

mouseclick-event