【從零開始學 Java 程式設計】JRadioButton 元件

【從零開始學 Java 程式設計】 線上教學課程目錄，使用 Java 程式語言，開發應用程式。

JRadioButton

JRadioButton 單選按鈕元件，可以提供很多選項，讓使用者單選

範例

學習如何使用 ButtonGroup 將三個 JRadioButton 變成一個單選群組，當使用者點選其中一個 JRadioButton 選項，下方 JLabel 元件，顯示剛選擇的項目名稱

關鍵程式碼

private JLabel jLabel;

public void addComponentsToPane(Container pane) {

    pane.setLayout(new BorderLayout());

    Box box = new Box(BoxLayout.Y_AXIS);

    ButtonGroup buttonGroup = new ButtonGroup();

    JRadioButton rbSpider = new JRadioButton("蜘蛛");
    rbSpider.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            updateChoice(rbSpider.getText());
        }
    });
    rbSpider.setAlignmentX(Component.CENTER_ALIGNMENT);
    buttonGroup.add(rbSpider);
    box.add(rbSpider);

    JRadioButton rbCockroach = new JRadioButton("蟑螂");
    rbCockroach.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            updateChoice(rbCockroach.getText());
        }
    });
    rbCockroach.setAlignmentX(Component.CENTER_ALIGNMENT);
    buttonGroup.add(rbCockroach);
    box.add(rbCockroach);

    JRadioButton rbfly = new JRadioButton("蒼蠅");
    rbfly.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            updateChoice(rbfly.getText());
        }
    });
    rbfly.setAlignmentX(Component.CENTER_ALIGNMENT);
    buttonGroup.add(rbfly);
    box.add(rbfly);

    jLabel = new JLabel("請選擇...");
    jLabel.setAlignmentX(Component.CENTER_ALIGNMENT);
    jLabel.setBorder(BorderFactory.createEmptyBorder(30, 0, 0, 0));
    box.add(jLabel);
    box.setBorder(BorderFactory.createEmptyBorder(30, 0, 0, 0));
    pane.add(box, BorderLayout.CENTER);
}

private void updateChoice(String text) {
    jLabel.setText("你選擇了： " + text);
}

完整程式碼

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

public class DemoJRadioButton {
    private JLabel jLabel;

    public void addComponentsToPane(Container pane) {

        pane.setLayout(new BorderLayout());

        Box box = new Box(BoxLayout.Y_AXIS);

        ButtonGroup buttonGroup = new ButtonGroup();

        JRadioButton rbSpider = new JRadioButton("蜘蛛");
        rbSpider.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                updateChoice(rbSpider.getText());
            }
        });
        rbSpider.setAlignmentX(Component.CENTER_ALIGNMENT);
        buttonGroup.add(rbSpider);
        box.add(rbSpider);

        JRadioButton rbCockroach = new JRadioButton("蟑螂");
        rbCockroach.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                updateChoice(rbCockroach.getText());
            }
        });
        rbCockroach.setAlignmentX(Component.CENTER_ALIGNMENT);
        buttonGroup.add(rbCockroach);
        box.add(rbCockroach);

        JRadioButton rbfly = new JRadioButton("蒼蠅");
        rbfly.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                updateChoice(rbfly.getText());
            }
        });
        rbfly.setAlignmentX(Component.CENTER_ALIGNMENT);
        buttonGroup.add(rbfly);
        box.add(rbfly);

        jLabel = new JLabel("請選擇...");
        jLabel.setAlignmentX(Component.CENTER_ALIGNMENT);
        jLabel.setBorder(BorderFactory.createEmptyBorder(30, 0, 0, 0));
        box.add(jLabel);
        box.setBorder(BorderFactory.createEmptyBorder(30, 0, 0, 0));
        pane.add(box, BorderLayout.CENTER);
    }

    private void updateChoice(String text) {
        jLabel.setText("你選擇了： " + text);
    }

    public DemoJRadioButton() {
        JFrame frame = new JFrame("HKT線上教室");
        // 獲取螢幕解析度
        Dimension dimension = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setSize(dimension.width / 4, dimension.height / 4);

        //設定視窗顯示在螢幕畫面中間位置
        int x = (int) ((dimension.getWidth() - frame.getWidth()) / 2);
        int y = (int) ((dimension.getHeight() - frame.getHeight()) / 2);
        frame.setLocation(x, y);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//設定關閉可以關掉程式
        //在 Pane 畫面中加入元件
        addComponentsToPane(frame.getContentPane());
//        frame.pack();
        frame.setVisible(true);
    }

    //最一開始程式進入點
    public static void main(String[] args) {
        //使用 invokeLater 確保 UI 在排程執行緒內
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new DemoJRadioButton();
            }
        });
    }
}

參考資料

• Java 8 API 官方說明書 - JRadioButton
• Oracle - The Java Tutorials : How to Use Buttons, Check Boxes, and Radio Buttons

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那這次的課程就介紹到這邊囉～

順帶一提，KT 線上教室，臉書粉絲團，會不定期發佈相關資訊，不想錯過最新資訊，不要忘記來按讚，加追蹤喔！也歡迎大家將這套課程分享給更多人喔。

我們下次再見囉！！！掰掰～