java - 填充 JPanel 底部的空白区域

Question

我正在手工编写一个自定义 JPanel，称之为 MyPanel，其中包含两个 JLabel 和两个 JTextBox。此 JPanel 将在 JFrame 中使用，该 JFrame 包含使用 CardLayout 的其他 JPanel。 JFrame 是不可调整大小的；它的大小是根据具有最多组件的 JPanel 固定的。

由于 MyPanel 的控件很少，我正试图找出最好的布局管理器来使用。我希望标签和文本字段显示在靠近顶部的位置，所有额外的空间都在底部。我相信 GridBagLayout 提供了让这个面板看起来像我想要的方式的功能。 MyPanel 具有以下从构造函数调用的 initComponents() 方法:

public class MyPanel extends JPanel {

    public static void main(String[] args) {
        JFrame frame = new JFrame("MyPanel Test");
        frame.add(new MyPanel(null));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 425);
        frame.setVisible(true);
    }

    public MyPanel() {
        initComponents();
    }

    private void initComponents() {
        this.setLayout(new GridBagLayout());

        JLabel cardYearLabel = new JLabel("Card Year:");
        cardYearLabel.setFont(new Font("Tahoma", 0, 14)); // NOI18N

        GridBagConstraints yearLabelConstraints = new GridBagConstraints();
        yearLabelConstraints.gridx = 0;
        yearLabelConstraints.gridy = 0;
        yearLabelConstraints.weightx = 1;
        yearLabelConstraints.weighty = 1;
        yearLabelConstraints.anchor = GridBagConstraints.WEST;
        yearLabelConstraints.insets = new Insets(20, 50, 10, 10);
        this.add(cardYearLabel, yearLabelConstraints);

        this.yearTextField = new JFormattedTextField();
        this.yearTextField.setFormatterFactory(new DefaultFormatterFactory(new NumberFormatter(new DecimalFormat("#0"))));
        this.yearTextField.setFont(new Font("Tahoma", 0, 14)); // NOI18N
        this.yearTextField.setColumns(10);
        this.yearTextField.addFocusListener(new UpdateInstructionsFocusListener("Enter card year."));

        GridBagConstraints yearTextFieldConstraints = new GridBagConstraints();
        yearTextFieldConstraints.gridx = 1;
        yearTextFieldConstraints.gridy = 0;
        yearTextFieldConstraints.weightx = 2;
        yearTextFieldConstraints.weighty = 1;
        yearTextFieldConstraints.fill = GridBagConstraints.HORIZONTAL;
        yearTextFieldConstraints.insets = new Insets(20, 10, 10, 50);
        this.add(this.yearTextField, yearTextFieldConstraints);

        JLabel cardNumberLabel = new JLabel("Card Number:");
        cardNumberLabel.setFont(new Font("Tahoma", 0, 14)); // NOI18N

        GridBagConstraints numberLabelConstraints = new GridBagConstraints();
        numberLabelConstraints.gridx = 0;
        numberLabelConstraints.gridy = 1;
        numberLabelConstraints.weightx = 1;
        numberLabelConstraints.weighty = 1;
        numberLabelConstraints.anchor = GridBagConstraints.WEST;
        numberLabelConstraints.insets = new Insets(10, 50, 0, 10);
        this.add(cardNumberLabel, numberLabelConstraints);

        this.numberTextField = new JFormattedTextField();
        this.numberTextField.setFormatterFactory(new DefaultFormatterFactory(new NumberFormatter(new DecimalFormat("#0"))));
        this.numberTextField.setFont(new Font("Tahoma", 0, 14)); // NOI18N
        this.numberTextField.setColumns(10);
        this.numberTextField.addFocusListener(new UpdateInstructionsFocusListener("Enter card number."));

        GridBagConstraints numberTextFieldConstraints = new GridBagConstraints();
        numberTextFieldConstraints.gridx = 1;
        numberTextFieldConstraints.gridy = 1;
        numberTextFieldConstraints.weightx = 2;
        numberTextFieldConstraints.weighty = 1;
        numberTextFieldConstraints.fill = GridBagConstraints.HORIZONTAL;
        numberTextFieldConstraints.insets = new Insets(10, 10, 0, 50);
        this.add(this.numberTextField, numberTextFieldConstraints);

        JPanel filler = new JPanel();
        GridBagConstraints fillerConstraints = new GridBagConstraints();
        fillerConstraints.gridx = 0;
        fillerConstraints.gridy = 2;
        fillerConstraints.gridwidth = 2;
        fillerConstraints.weightx = 1;
        fillerConstraints.weighty = 100;
        this.add(filler, fillerConstraints);
    }
}

我不敢使用空白的 JPanel 来填充 MyPanel 底部的空白区域。有没有更好、更优雅的方法来做到这一点？ (我并没有坚持使用 GridBagLayout。如果另一个标准的 LayoutManager 可以做到这一点，我完全赞成。)

Answer 1

实现此目的的一种方法是将控件放在一个面板中，然后将该面板添加到具有 BorderLayout 的第二个面板的 PAGE_START。