如何设置 JFrame 大小以适合 CardLayout 显示的 JPanel?

2022-01-24 00:00:00 java swing jpanel jframe cardlayout

我有一个 JFrame，在 CardLayout 中包含一组 JPanels.每个 JPanel 都有不同的大小，我希望 JFrame 适应当前显示的 JPanel 的大小(而不是 JPanel 来适应 JFrame 的大小).

I have a JFrame containing a set of JPanels in a CardLayout. Each JPanel has a different size and I want the JFrame to adapt to the size of the currently displayed JPanel (not the JPanel to adapt to the size of the JFrame).

我怎样才能做到这一点?

How can I achieve this?

推荐答案

一般是:如果你有布局问题，总是用合适的 LayoutManager 解决.切勿调整组件的大小提示以达到您的目标.

The general is: if you have a layout problem, always solve it with an appropriate LayoutManager. Never tweak a component's sizing hint to reach your goal.

在这种情况下，调整 CardLayout 尤其容易.默认情况下，它会将其 prefSize 计算为所有卡的 prefSize 的最大值.只需子类化并实现以返回当前可见卡片的 prefSize(加上 insets):

In this case, it's particularly easy to adjust the CardLayout. By default, it calculates its prefSize to the max of prefSizes of all cards. Simply subclass and implement to return the prefSize (plus insets) of the currently visible card:

public static class MyCardLayout extends CardLayout {

    @Override
    public Dimension preferredLayoutSize(Container parent) {

        Component current = findCurrentComponent(parent);
        if (current != null) {
            Insets insets = parent.getInsets();
            Dimension pref = current.getPreferredSize();
            pref.width += insets.left + insets.right;
            pref.height += insets.top + insets.bottom;
            return pref;
        }
        return super.preferredLayoutSize(parent);
    }

    public Component findCurrentComponent(Container parent) {
        for (Component comp : parent.getComponents()) {
            if (comp.isVisible()) {
                return comp;
            }
        }
        return null;
    }

}

使用它(借用@mKorbel 的示例)，主要方法干净利落地缩小:

Using that (borrowing @mKorbel's example), the main method cleanly shrinks down:

private static void createAndShowUI() {
    final CardLayout cardLayout = new MyCardLayout();
    final JPanel cardHolder = new JPanel(cardLayout);
    final JFrame frame = new JFrame("MultiSizedPanels");
    JLabel[] labels = {
        new JLabel("Small Label", SwingConstants.CENTER),
        new JLabel("Medium Label", SwingConstants.CENTER),
        new JLabel("Large Label", SwingConstants.CENTER)};

    for (int i = 0; i < labels.length; i++) {
        int padding = 50 * (i + 1);
        Border lineBorder = BorderFactory.createCompoundBorder(
            BorderFactory.createLineBorder(Color.blue),
            BorderFactory.createEmptyBorder(padding, padding, padding, padding));
        labels[i].setBorder(lineBorder);
        JPanel containerPanel = new JPanel();
        containerPanel.add(labels[i]);
        cardHolder.add(containerPanel, String.valueOf(i));
    }
    JButton nextButton = new JButton("Next");
    nextButton.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            cardLayout.next(cardHolder);
            frame.pack();
        }
    });
    JPanel btnHolder = new JPanel();
    btnHolder.add(nextButton);

    frame.add(cardHolder, BorderLayout.CENTER);
    frame.add(btnHolder, BorderLayout.SOUTH);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocation(150, 150);
    frame.setVisible(true);
}

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