Question

我想在同一JFrame上使用2个按钮分别执行不同的任务。一个用于更改右侧的标签，另一个用于更改中间圆圈的颜色。（随机变化的颜色在另一个类上。）

由于某些未知原因，程序似乎无法识别主类（类TwoButtons）中存在的内部类。我对java很新，我找不到我做错了什么....你能帮我解决一下我的问题吗？

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

public class TwoButtons {
    JFrame frame;
    JLabel label;


    public static void main(String[] args) {
        TwoButtons gui = new TwoButtons();
        gui.go();

    }
    public void go(){
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JButton labelButton = new JButton("Change label");
        labelButton.addActionListener(new LabelListener());

        JButton colorButton = new JButton("Change cirle");
        colorButton.addActionListener(new ColorListener());

        label = new JLabel("I'm a labele");
        MyDrawPanel drawPanel = new MyDrawPanel();

        frame.getContentPane().add(BorderLayout.SOUTH, colorButton);
        frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
        frame.getContentPane().add(BorderLayout.WEST, labelButton);
        frame.getContentPane().add(BorderLayout.EAST, label);
        frame.setSize(300, 300);
        frame.setVisible(true);

        class LabelListener implements ActionListener {
            public void actionPerformed(ActionEvent event) {
            label.setText("Ouch!");

            }
        }
        class ColorListener implements ActionListener {
            public void actionPerformed(ActionEvent event) {
            frame.repaint();
            }
        }


        }


    }

我在

上收到错误

labelButton.addActionListener(new LabelListener());

和

colorButton.addActionListener(new ColorListener());

在两种情况下都说LabelListener和ColorListener都无法解析为类型非常感谢你提前.. !!

Answer 1

您需要将类 LabelListener 和 ColorListener 移出public void go（）方法

class LabelListener implements ActionListener {
    public void actionPerformed(ActionEvent event) {
        label.setText("Ouch!");
    }
}

和

class ColorListener implements ActionListener {
    public void actionPerformed(ActionEvent event) {
        frame.repaint();
    }
}

Answer 2

在java中，您不能在使用它们之后在方法中定义类（就像方法中的变量一样），因此，尝试在ColorListener中定义类LabelListener和class TwoButtons而不是在go方法中定义它们，如下所示:(这通常是更好的做法）

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

public class TwoButtons {
    JFrame frame;
    JLabel label;

    public static void main(String[] args) {
        TwoButtons gui = new TwoButtons();
        gui.go();
    }

    public void go(){
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JButton labelButton = new JButton("Change label");
        labelButton.addActionListener(new LabelListener());

        JButton colorButton = new JButton("Change cirle");
        colorButton.addActionListener(new ColorListener());

        label = new JLabel("I'm a labele");
        MyDrawPanel drawPanel = new MyDrawPanel();

        frame.getContentPane().add(BorderLayout.SOUTH, colorButton);
        frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
        frame.getContentPane().add(BorderLayout.WEST, labelButton);
        frame.getContentPane().add(BorderLayout.EAST, label);
        frame.setSize(300, 300);
        frame.setVisible(true);
    }

    class LabelListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            label.setText("Ouch!");
        }
    }

    class ColorListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            frame.repaint();
        }
    }
}

程序无法识别java

2 个答案: