Question

我无法将Panel类放到主类中。我似乎无法实例化并将按钮注册到actionPerformed方法。这个项目假设使用带有9个输入按钮的网格布局（其他3个按钮用于输入，空格和清除）然后在JTextArea上显示输入。我相信我已经正确设置了Panel类，但是在将JButton数组放在一起时会出现问题，然后将其注册到actionPerformed方法。任何指针都将非常感激。（附带问题，如何将代码复制并粘贴到代码块中？）

import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class TextButtons extends JFrame implements ActionListener {

    private JButton[] buttons;
    private JTextArea textArea;
    private final int ENTER;   //Index of Enter button in buttons
    private final int SPACE;    //Index of Space button in buttons
    private final int CLEAR;    //Index of Clear button in buttons

    public TextButtons(String title) {
        super(title);
        JFrame frame = new JFrame("Text Button");

        //TODO: instantiate all JButtons, add them to the buttons array,
        //  and register "this" as the ActionListener for each button.

        for (int i = 0; i < buttons.length; i++) {
            buttons[i] = new JButton();
            //this.buttons.addActionListener(e);
        }

        ENTER = 9;
        SPACE = 10;
        CLEAR = 11;
        buttons[ENTER] = new JButton("\n");
        buttons[SPACE] = new JButton(" ");
        buttons[CLEAR] = new JButton("clear");

        JTextArea textArea = new JTextArea();
        textArea.setEditable(false);

        TextButtonsPanel mainPanel = new TextButtonsPanel(buttons, textArea);

        this.getContentPane().add(mainPanel);
        this.pack();
        this.setVisible(true);
    }

    /* (non-Javadoc)
     * @see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
     */
    @Override
    public void actionPerformed(ActionEvent e) {
        // ??
    }

    public static void main(String[] args) {
        final TextButtons f = new TextButtons("Text Buttons");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

PanelClass

    public class TextButtonsPanel extends JPanel {

        public TextButtonsPanel(JButton[] buttons, JTextArea textArea) {

            int ENTER = 11;

            JPanel mainPanel = new JPanel(new GridLayout(4, 3));

            JButton b1 = new JButton("A");
            JButton b2 = new JButton("B");
            JButton b3 = new JButton("C");
            JButton b4 = new JButton("1");
            JButton b5 = new JButton("2");
            JButton b6 = new JButton("3");
            JButton b7 = new JButton("X");
            JButton b8 = new JButton("Y");
            JButton b9 = new JButton("Z");

            add(b1);
            mainPanel.add(b2);
            mainPanel.add(b3);
            mainPanel.add(b4);
            mainPanel.add(b5);
            mainPanel.add(b6);
            mainPanel.add(b7);
            mainPanel.add(b8);
            mainPanel.add(b9);

            JScrollPane scrollPane = new JScrollPane(textArea);
            scrollPane.setPreferredSize(new Dimension(80, 120));
            mainPanel.add(scrollPane);
        }
    }
}

Answer 1

您的TextButtonsPanel延伸JPanel，但是您要将JPanel的所有内容添加到名为mainPanel的{{1}}，这些内容永远不会添加到任何内容中。

由于JButton是本地变量，因此您永远无法将外部ActionListener附加到其中。不确定这是好事还是坏事。

我会创建一个只包含按钮的TextButtonsPane，没有其他组件。它只是生成事件。

我会提供一个addActionListener和removeActionListener，它只会根据其中包含的所有按钮注册监听器。

这样，按钮窗格并不关心它的用途，它只是生成其他可以使用的事件。

您可能需要一些时间来阅读Creating a GUI with Swing

Answer 2

我似乎无法实例化并将按钮注册到actionPerformed方法。

您可以像这样组织代码：

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

class TextButtonPanel extends JPanel implements ActionListener {

    public TextButtonPanel(String[] labels) {
        setLayout(new GridLayout(0, 3));  //same as self.setLayout(..)

        JButton button;

        for (String label : labels) {
            button = new JButton(label);
            button.addActionListener(this);
            add(button);  //same as self.add(button)
        }
    }   

    public void actionPerformed(ActionEvent e) {
        JButton button = (JButton) e.getSource();
        System.out.println(button.getText());
    }

}


class MyGui {

    public MyGui() {
        JFrame frame = new JFrame("Name");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.setBounds(200, 100, 500, 300);
        Container cpane = frame.getContentPane();

        String[] labels = {"A", "B", "C", "D"};
        TextButtonPanel panel = new TextButtonPanel(labels);
        cpane.add(panel);

        frame.setVisible(true);
    }
}



public class SwingProg {
    private static void createAndShowGUI() {
        new MyGui();
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

JPanel，实例化一个JButton数组

2 个答案: