如何设置JFrame大小以适合显示JPanel的CardLayout？ [英] How to set a JFrame size to fit the CardLayout displayed JPanel?

问题描述

我在 CardLayout JFrame ，其中包含一组 JPanels C $ C>。每个 JPanel 都有不同的大小，我希望 JFrame 适应当前显示的<$ c $的大小c> JPanel （不是 JPanel 以适应 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).

我怎样才能实现这个目标？

How can I achieve this?

推荐答案

一般是：如果您有布局问题，始终使用适当的LayoutManager解决它。 从不调整组件的大小提示以达到目标。

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特别容易。默认情况下，它会将prefSize计算为所有卡的prefSizes的最大值。简单地子类化并实现以返回当前可见卡片的prefSize（加上插图）：

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的例子），主要方法干净利落：

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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