在 JScrollBar 中自动换行的布局

Question

我正在尝试构建一个组件水平放置的面板，如果没有足够的空间则自动换行，还有一个垂直滚动条。

像这样：

+-----------------+
|[1][2][3][4][5]  |
|                 | 
+-----------------+

减小宽度：

+-----------+
|[1][2][3]  |
|[4][5]     |
+-----------+

再次缩小宽度，出现滚动条：

+---------+
|[1][2]  ^|
|[3][4]  v|
+---------+

我离解决方案不远了：

public class TestFlow extends JFrame {

    public TestFlow() {

        getContentPane().setLayout(new BorderLayout());

        JPanel panel = new JPanel(new FlowLayout());
        JScrollPane scroll = new JScrollPane(panel, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        getContentPane().add(scroll, BorderLayout.CENTER);

        panel.add(new MyComponent("A"));
        panel.add(new MyComponent("B"));
        panel.add(new MyComponent("C"));
        panel.add(new MyComponent("D"));
        panel.add(new MyComponent("E"));
        panel.add(new MyComponent("F"));
        panel.add(new MyComponent("G"));
        panel.add(new MyComponent("H"));
        panel.add(new MyComponent("I"));
        panel.add(new MyComponent("J"));
        panel.add(new MyComponent("K"));
        panel.add(new MyComponent("L"));
        panel.add(new MyComponent("M"));
        panel.add(new MyComponent("N"));
        panel.add(new MyComponent("O"));

        scroll.addComponentListener(new ComponentAdapter() {

            @Override
            public void componentResized(ComponentEvent e) {
                Dimension max=((JScrollPane)e.getComponent()).getViewport().getExtentSize();
//                panel.setMaximumSize(new Dimension(max.width,Integer.MAX_VALUE));
                panel.setPreferredSize(new Dimension(max.width,Integer.MAX_VALUE));
//                panel.setPreferredSize(max);
                panel.revalidate();
//                panel.repaint();
//                System.out.println(panel.getSize().width+"--"+max.width);
            }

        });

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(500, 200);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new TestFlow().setVisible(true));
    }

    private static class MyComponent extends JLabel {

        public MyComponent(String text) {
            super(String.join("", Collections.nCopies((int)(Math.round(Math.random()*4)+4), text)));
            setOpaque(true);
            setBackground(Color.YELLOW);
        }

    }

}

，但仍然有奇怪的行为：

有了解决方案panel.setPreferredSize(new Dimension(max.width,Integer.MAX_VALUE));

调整 window 的大小后，面板变空了。我必须手动移动滚动条才能显示内容
滚动条始终可见，但不应该

有了解决方案panel.setPreferredSize(max);

调整 window 大小后，面板不会重新布局。我必须再次手动移动 window 以重新布局内容。
滚动条永远不可见，而它应该。

该代码有什么建议吗？

[编辑] 我已将原始代码复杂化，并应用了迄今为止提供的建议。

出于设计目的，我想在面板顶部使用 MigLayout。一开始，一切都布置得很好。当放大 window 时，它也有效。但不是减少window。 addComponentListener没有带来任何附加值。

public class TestMigFlow extends JFrame {

    public TestMigFlow() {

        getContentPane().setLayout(new BorderLayout());
        JPanel panel = new JPanel(new MigLayout("debug, fill, flowy", "[fill]"));
        JScrollPane scroll = new JScrollPane(panel, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        getContentPane().add(scroll, BorderLayout.CENTER);

        panel.add(new JLabel("A title as spearator "), "growy 0");

        JPanel sub = new JPanel(new WrapLayout());
//        panel.add(sub, "growx 0"); // Works well on shrink but not on grow
        panel.add(sub); // Works well on grow but not on shrink

        sub.add(new MyComponent("A"));
        sub.add(new MyComponent("B"));
        sub.add(new MyComponent("C"));
        sub.add(new MyComponent("D"));
        sub.add(new MyComponent("E"));
        sub.add(new MyComponent("F"));
        sub.add(new MyComponent("G"));
        sub.add(new MyComponent("H"));
        sub.add(new MyComponent("I"));
        sub.add(new MyComponent("J"));
        sub.add(new MyComponent("K"));
        sub.add(new MyComponent("L"));
        sub.add(new MyComponent("M"));
        sub.add(new MyComponent("N"));
        sub.add(new MyComponent("O"));

        addComponentListener(new ComponentAdapter() {

            @Override
            public void componentResized(ComponentEvent e) {
                Dimension max = new Dimension(scroll.getWidth(), Short.MAX_VALUE);
                panel.setMaximumSize(max);
                panel.repaint();
            }

        });

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(200, 500);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new TestMigFlow().setVisible(true));
    }

    private static class MyComponent extends JLabel {

        public MyComponent(String text) {
            super(String.join("", Collections.nCopies((int) (Math.round(Math.random() * 4) + 4), text)));
            setOpaque(true);
            setBackground(Color.YELLOW);
        }

    }

Answer 1

下面的代码适合我。

我已将代码拆分为一个组件，该组件执行所有布局和测试代码以验证它是否有效（在 static main 中）方法。

我没有挂钩以调整 JScrollPane 上的事件大小，而是在整个 TestFlow (TF) 组件上这样做 - 我相信这是等效的，但它似乎更安全。每当调整 TF 大小时，我都会更新面板的首选大小，就像您所做的一样 - 但有两个步骤您没有采取：

内面板的宽度将与外面板指定的宽度相同，但如果需要，还应为垂直滚动条留出足够的 space。
内部面板的高度应该是它显示的最低组件的高度。在我的例子中，我采取了假设最低行中的所有组件高度相同的捷径，但这不一定总是正确的。

深入研究 Swing 如何处理布局和绘画，以及调用几个看起来相似的方法中的哪些方法时，总是让我想起黑魔法。

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

public class TestFlow extends JPanel {

    JPanel panel;
    JScrollPane scroll;

    public TestFlow() {
        panel = new JPanel(new FlowLayout());
        scroll = new JScrollPane(panel, 
            ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, 
            ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        setLayout(new BorderLayout());
        add(scroll, BorderLayout.CENTER);
        addComponentListener(new ComponentAdapter(){
            @Override
            public void componentResized(ComponentEvent e){
                Rectangle lastChildBounds = panel
                    .getComponent(panel.getComponentCount() - 1).getBounds();
                Dimension preferred = new Dimension(
                    scroll.getWidth(), 
                    lastChildBounds.y + lastChildBounds.height);
                if (scroll.getVerticalScrollBar().isVisible()) {
                    preferred.width -= scroll.getVerticalScrollBar().getWidth();
                }
                // System.err.println("setting inner panel size to " + preferred);
                panel.setPreferredSize(preferred);
                panel.repaint();
            }
        });
    }

    public JPanel getInnerPanel() { return panel; }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            // get a TestFlow instance and fill it with random labels
            TestFlow tf = new TestFlow();
            Random r = new Random();
            for (String s : "A B C D E F G H I J K L M N O".split(" ")) {
                String labelText = String.join("", Collections.nCopies(4+r.nextInt(3)*4, s));
                JLabel label = new JLabel(labelText);
                label.setOpaque(true);
                label.setBackground(Color.YELLOW);
                tf.getInnerPanel().add(label);
            }

            // display it in a window
            JFrame jf = new JFrame("test");
            jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);            
            jf.add(tf, BorderLayout.CENTER);
            jf.setSize(500, 200);
            jf.setLocationRelativeTo(null);
            jf.setVisible(true);
        });
    }
}

Answer 2

可能我误解了你的问题，但是当我添加 revalidate 调用时，面板缩小时一切正常。

Dimension max = new Dimension(scroll.getWidth(), Short.MAX_VALUE);
panel.setMaximumSize(max);
// trigger layout recalculation
panel.revalidate();
panel.repaint();

这里有一些复杂的改进（以便在需要时更好地考虑滚动条和布局的大小 ;)

public class TestMigFlow extends JFrame {
    private Integer layoutDecr;

    public TestMigFlow() {

        getContentPane().setLayout(new BorderLayout());
        JPanel panel = new JPanel(new MigLayout("debug, fill, flowy", "[fill]"));
        JScrollPane scroll =
                new JScrollPane(panel, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        getContentPane().add(scroll, BorderLayout.CENTER);

        panel.add(new JLabel("A title as spearator "), "growy 0");

        JPanel sub = new JPanel(new WrapLayout());
        // panel.add(sub, "growx 0"); // Works well on shrink but not on grow
        panel.add(sub); // Works well on grow but not on shrink

        sub.add(new MyComponent("A"));
        sub.add(new MyComponent("B"));
        sub.add(new MyComponent("C"));
        sub.add(new MyComponent("D"));
        sub.add(new MyComponent("E"));
        sub.add(new MyComponent("F"));
        sub.add(new MyComponent("G"));
        sub.add(new MyComponent("H"));
        sub.add(new MyComponent("I"));
        sub.add(new MyComponent("J"));
        sub.add(new MyComponent("K"));
        sub.add(new MyComponent("L"));
        sub.add(new MyComponent("M"));
        sub.add(new MyComponent("N"));
        sub.add(new MyComponent("O"));

        addComponentListener(new ComponentAdapter() {

            @Override
            public void componentResized(ComponentEvent e) {
                if (layoutDecr == null && panel.getWidth() > 0) {
                    layoutDecr = panel.getWidth() - sub.getWidth();
                }
                JScrollBar vBar = scroll.getVerticalScrollBar();
                int decr = vBar.isVisible() ? vBar.getPreferredSize().width : 0;
                decr += layoutDecr == null ? 0 : layoutDecr;
                Dimension max = new Dimension(scroll.getWidth() - decr, Short.MAX_VALUE);
                sub.setMaximumSize(max);
                sub.revalidate();
                sub.repaint();
            }

        });

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(200, 500);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> new TestMigFlow().setVisible(true));
    }

    private static class MyComponent extends JLabel {

        public MyComponent(String text) {
            super(String.join("", Collections.nCopies((int) (Math.round(Math.random() * 4) + 4), text)));
            setOpaque(true);
            setBackground(Color.YELLOW);
        }

    }
}

Answer 3

解决方案是

等待面板容器的大小调整完毕。因此 addComponentListener 在面板级别而不是帧级别
使用 WrapLayout
依靠 WrapLayout 的 preferredLayoutSize 计算面板的适当大小
在 MigLayout

调整 window 大小时，解决方案的反面有点闪烁。

public class TestMigFlow2 extends JFrame {

    public TestMigFlow2() {

        getContentPane().setLayout(new BorderLayout());
        JPanel panel = new JPanel(new MigLayout("fillx, flowy", "[fill]"));
        JScrollPane scroll
                = new JScrollPane(panel, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        getContentPane().add(scroll, BorderLayout.CENTER);

        panel.add(new MySeparator("sep1"), "growy 0, shrinky 100");

        JPanel sub = new JPanel(new WrapLayout());
        panel.add(sub, "shrinky 100"); // Works well on grow but not on shrink

        sub.add(new MyComponent("A"));
        sub.add(new MyComponent("B"));
        sub.add(new MyComponent("C"));
        sub.add(new MyComponent("D"));
        sub.add(new MyComponent("E"));
        sub.add(new MyComponent("F"));
        sub.add(new MyComponent("G"));
        sub.add(new MyComponent("H"));
        sub.add(new MyComponent("I"));
        sub.add(new MyComponent("J"));
        sub.add(new MyComponent("K"));
        sub.add(new MyComponent("L"));
        sub.add(new MyComponent("M"));
        sub.add(new MyComponent("N"));
        sub.add(new MyComponent("O"));

        panel.add(new MySeparator("sep2"), "growy 0, shrinky 100");

        panel.addComponentListener(new ComponentAdapter() {
            @Override
            public void componentResized(ComponentEvent e) {

                WrapLayout wl = (WrapLayout) sub.getLayout();
                Dimension prefdim = wl.preferredLayoutSize(sub);
                sub.setPreferredSize(prefdim);
                panel.revalidate();
                panel.repaint();
            }

        });

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(200, 500);
        setLocationRelativeTo(null);
    }

这同样适用于 BoxLayout 而不是 MigLayout 添加了 2 个：

添加 VerticulGlue 作为最后一个元素

为面板指定最大高度以防止 BoxLayout 在面板和垂直胶水之间共享额外的 space。

public TestBoxLayout() {

    getContentPane().setLayout(new BorderLayout());
    JPanel panel = new JPanel();
    BoxLayout layout = new BoxLayout(panel, BoxLayout.PAGE_AXIS);
    panel.setLayout(layout);
    JScrollPane scroll
            = new JScrollPane(panel, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

    getContentPane().add(scroll, BorderLayout.CENTER);

    JLabel separator;
    separator = new MySeparator("Sep1");
    panel.add(separator);

    JPanel sub = new MyPanel(new WrapLayout());
    sub.setAlignmentX(0f);
    panel.add(sub);

    sub.add(new MyComponent("A"));
    sub.add(new MyComponent("B"));
    sub.add(new MyComponent("C"));
    sub.add(new MyComponent("D"));
    sub.add(new MyComponent("E"));
    sub.add(new MyComponent("F"));
    sub.add(new MyComponent("G"));
    sub.add(new MyComponent("H"));
    sub.add(new MyComponent("I"));
    sub.add(new MyComponent("J"));
    sub.add(new MyComponent("K"));
    sub.add(new MyComponent("L"));
    sub.add(new MyComponent("M"));
    sub.add(new MyComponent("N"));
    sub.add(new MyComponent("O"));

    separator = new MySeparator("Sep2");
    panel.add(separator);

    // -- Un filler --
    panel.add(Box.createVerticalGlue());


    panel.addComponentListener(new ComponentAdapter() {
        @Override
        public void componentResized(ComponentEvent e) {

            WrapLayout wl=(WrapLayout) sub.getLayout();
            Dimension prefdim=wl.preferredLayoutSize(sub);
            sub.setPreferredSize(prefdim);
            // Force the max height = pref height to prevent the BoxLayout dispatching the remaining height between the panel and the glue.
            Dimension maxdim=new Dimension(Short.MAX_VALUE,prefdim.height);
            sub.setMaximumSize(maxdim);
            panel.revalidate();
            panel.repaint();
        }

    });

    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(200, 500);
    setLocationRelativeTo(null);
}

在 JScrollBar 中自动换行的布局

Layout with auto-wrap within JScrollBar

java

swing

jscrollpane

miglayout

flowlayout