Question

我正在运行一个已编程的游戏，但我得到四个错误，这些错误都是javax.swing.AbstractButton类型中的方法addActionListener不适用于参数（DisplayArea）。我已确保所有内容都已正确导入，但我是java的新用户，可能会遗漏格式错误。

GUI.java

import java.awt.BorderLayout;
import java.awt.Color;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.AbstractButton;

public class GUI extends JFrame { 

private JButton bleft;
private JButton bRight;
private JButton bUp;
private JButton bDown;

private String[] colors;
private JComboBox colorList;
public DisplayArea display;

public GUI() {

    super("Lab 4: Simple GUI");

    setBackground(Color.white);
    setSize(DisplayArea.SCREEN_SIZE, DisplayArea.SCREEN_SIZE + 50);
    setResizable(false);
    setDefaultCloseOperation(EXIT_ON_CLOSE);

    //Initializes the variable

    bleft = new JButton("Left");
    bRight = new JButton("Right");
    bUp = new JButton("Up");
    bDown = new JButton("Down");

    colors = new String []{"red", "black", "blue", "green"};
    colorList = new JComboBox(colors);

    display = new DisplayArea();

    add(display, BorderLayout.CENTER);

    JPanel buttonpanel = new JPanel();
    buttonpanel.add(bleft);
    buttonpanel.add(bRight);
    buttonpanel.add(bUp);
    buttonpanel.add(bDown);
    buttonpanel.add(colorList);

    add(buttonpanel, BorderLayout.SOUTH);

    bleft.addActionListener(display);  //ERROR 
    bRight.addActionListener(display); //ERROR
    bUp.addActionListener(display);    //ERROR
    bDown.addActionListener(display);  //ERROR

}

public static void main(String [] args) {

    GUI gui = new GUI();
    gui.setVisible(true);
}

}

DisplayArea.java

import javax.swing.JPanel;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JComboBox;
import javax.swing.JButton;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListene

public class DisplayArea extends JPanel {

public static final int SCREEN_SIZE = 500;
public static final int DELTA = 10;

private Color currentColor;
private Point center;

public DisplayArea(){

    setSize(SCREEN_SIZE, SCREEN_SIZE);
    center = new Point(SCREEN_SIZE/2, SCREEN_SIZE/2);
    currentColor = Color.RED;

}

@Override
public void paint(Graphics g){

    super.paint(g);
    g.setColor(currentColor);
    g.fillOval(center.x, center.y, 10, 10);
}

public void actionPerformed (ActionEvent e){

    if(e.getSource() instanceof JButton) {

        String cmd = e.getActionCommand();

        if(cmd.equals("Left")){
            center.x = center.x - DELTA;
        } else if (cmd.equals("Right")){
            center.x = center.x + DELTA;
        } else if (cmd.equals("Up")){
            center.y = center.y + DELTA;
        } else if (cmd.equals("Down")){
            center.y = center.y - DELTA;
        }
}

repaint();

}

}

Answer 1

正如@LuxxMiner所指出的，传递给addActionListener的值必须是ActionListener类型。一种选择是声明匿名内部类，如下所示：

bleft.addActionListener(new AbstractAction() {
    @Override
    public void actionPerformed(ActionEvent arg0) {
        //Do stuff here
    }
});

方法addActionListener，类型为javax.swing.AbstractButton

1 个答案: