Java 为什么JScrollPane中的JPanel不滚动？

我在

JScrollPane

中放置了一个

JPanel

（黄色）

当我在

JTextPane

中输入一些文本时，它会调整大小，但垂直滚动条仍然不活动

yelowPanel.getSize（）

返回与以前相同的值。`（您可以在redPanel上看到它）

那么如何刷新黄色面板？我想垂直滚动面板。 我试图：

panelCreating.revalidate();
panelCreating.invalidate();
panelCreating.repaint();

仅适用于

panelCreating.setPreferredSize（新维度（333777））但我不知道该设置什么尺寸。这取决于内容

有一个小例子：

package swingtest;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;

public class SwingTest extends JFrame {

    public SwingTest() {
        initComponents();
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new SwingTest().setVisible(true);
            }
        });
    }
    private JPanel panelCenter, panelCreating;
    private JScrollPane scrollPaneCreating, scrollPaneCenter;
    private JTextPane textPane1, textPane2;
    private JButton button1;

    private void initComponents() {
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setMinimumSize(new Dimension(300, 300));

        panelCreating = new JPanel();
        panelCreating.setMinimumSize(new Dimension(160, 200));
        panelCreating.setPreferredSize(new Dimension(160, 200));
        scrollPaneCreating = new JScrollPane(panelCreating,
            JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
            JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

        textPane1 = new JTextPane();
        textPane1.setText("a\na");
        textPane2 = new JTextPane();
        textPane2.setText("b\nb");
        button1 = new JButton("+++");

        panelCenter = new JPanel();
        panelCenter.setBackground(Color.blue);
        scrollPaneCenter = new JScrollPane(panelCenter);



        // ----------------- Left Panel Init -----------------------

        panelCreating.setLayout(new GridBagLayout());
        panelCreating.setBackground(Color.ORANGE);
        panelCreating.setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));

        GridBagConstraints c = new GridBagConstraints();
        c.insets = new Insets(0, 0, 4, 4);
        c.anchor = GridBagConstraints.FIRST_LINE_START;
        c.weightx = c.weighty = 0;

        c.gridx = 0;
        c.gridy = GridBagConstraints.RELATIVE;
        c.gridwidth = GridBagConstraints.REMAINDER;
        c.gridheight = 1;
        c.fill = GridBagConstraints.BOTH;
        panelCreating.add(textPane1, c);

        button1.addActionListener(new ActionListener() {

            int height = 50;

            @Override
            public void actionPerformed(ActionEvent e) {
                textPane1.setText(textPane1.getText() + "\na");
                textPane1.setPreferredSize(new Dimension(150, height));
                textPane2.setText(textPane2.getText() + "\nb");
                textPane2.setPreferredSize(new Dimension(150, height));
                height += 30;

                panelCreating.revalidate();
                panelCreating.repaint();
                scrollPaneCreating.revalidate();
            }
        });
        panelCreating.add(button1, c);

        panelCreating.add(textPane2, c);

        // -------------------------------------------------------

        getContentPane().setLayout(new GridBagLayout());
        c = new GridBagConstraints();

        c.ipadx = c.ipady = 0;
        c.insets = new Insets(0, 0, 0, 0);
        c.weighty = 0;
        c.gridheight = 1;
        c.gridx = 0;
        c.gridy = 1;
        c.gridwidth = 1;
        c.weightx = 0;
        c.fill = GridBagConstraints.BOTH;
        getContentPane().add(scrollPaneCreating, c);


        c.gridx = 1;
        c.gridy = 1;
        c.fill = GridBagConstraints.BOTH;
        c.weightx = 1;
        c.weighty = 1;
        getContentPane().add(scrollPaneCenter, c);

    }
}

黄色面板也使用GridBagLayout。
对不起，我的英语是
JPanel
的默认布局是
FlowLayout
。尝试
GridLayout
。有一个相关的例子。比如说,

panelCreating = new JPanel(new GridLayout());
scrollPaneCreating = new JScrollPane(panelCreating);

附录：也考虑嵌套布局。下面的示例使用左面板的
BoxLayout

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;

/** @see https://stackoverflow.com/questions/9184476 */
public class SwingTest extends JFrame {

    private static final int N = 8;

    public SwingTest() {
        initComponents();
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new SwingTest().setVisible(true);
            }
        });
    }
    private JPanel panelCenter, panelCreating;
    private JScrollPane scrollPaneCreating, scrollPaneCenter;

    private void initComponents() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        panelCreating = new JPanel();
        scrollPaneCreating = new JScrollPane(panelCreating,
            JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
            JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);

        panelCenter = new JPanel();
        panelCenter.setBackground(Color.blue);
        scrollPaneCenter = new JScrollPane(panelCenter);

        // ----------------- Left Panel Init -----------------------
        panelCreating.setLayout(new BoxLayout(panelCreating, BoxLayout.Y_AXIS));
        panelCreating.setBackground(Color.orange);
        panelCreating.setBorder(BorderFactory.createEmptyBorder(N, N, N, N));

        panelCreating.add(createTextPane());
        panelCreating.add(Box.createVerticalStrut(N));
        panelCreating.add(createTextPane());
        panelCreating.add(Box.createVerticalStrut(N));
        panelCreating.add(createTextPane());

        // -------------------------------------------------------
        setLayout(new GridLayout(1, 0));
        add(scrollPaneCreating);
        add(scrollPaneCenter);
        pack();
    }

    private JTextPane createTextPane() {
        JTextPane pane = new JTextPane();
        pane.setText(""
            + "Twas brillig and the slithy toves\n"
            + "Did gyre and gimble in the wabe;\n"
            + "All mimsy were the borogoves,\n"
            + "And the mome raths outgrabe.");

        pane.setBorder(BorderFactory.createEmptyBorder(N, N, N, N));
        return pane;
    }
}


不要在
面板creating
上设置首选大小，而是在
滚动面板creating
上设置它。并且不要在文本组件上设置首选大小，它们会随着您添加新的文本行而增长。这样做的目的是让滚动窗格中的面板按需要增大，并限制滚动窗格本身的大小

    // [...]

    panelCreating = new JPanel();
    //panelCreating.setMinimumSize(new Dimension(160, 200));
    //panelCreating.setPreferredSize(new Dimension(160, 200));
    scrollPaneCreating = new JScrollPane(panelCreating,
        JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, 
        JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    scrollPaneCreating.setMinimumSize(new Dimension(160, 200));
    scrollPaneCreating.setPreferredSize(new Dimension(160, 200));

    // [...]

        @Override
        public void actionPerformed(ActionEvent e) {
            textPane1.setText(textPane1.getText() + "\na");
            //textPane1.setPreferredSize(new Dimension(150, height));
            textPane2.setText(textPane2.getText() + "\nb");
            //textPane2.setPreferredSize(new Dimension(150, height));
            //height += 30;

            // This isn't necessary either
            //panelCreating.revalidate();
            //panelCreating.repaint();
            //scrollPaneCreating.revalidate();
        }


编辑以添加：另一种选择是在附加到滚动窗格的
JViewport
上设置大小。视口是显示内容的位置。您可以将滚动窗格视为由视口和滚动条组成。如果滚动窗格设置为固定大小，则通过减去滚动条大小来确定视口大小。但如果视口设置为固定大小，则滚动窗格大小将通过将滚动条大小添加到视口大小来确定。如果要精确控制屏幕上显示的内容量，最好在视口中设置固定大小，因为滚动条大小可能因操作系统而异

scrollPaneCreating.getViewport().setMinimumSize(new Dimension(160, 200));
scrollPaneCreating.getViewport().setPreferredSize(new Dimension(160, 200));

我修复了添加一行时出现的问题

panelCreating.setPreferredSize(new Dimension((int) panelCreating.getPreferredSize().getWidth(),
                    (int)(panelCreating.getPreferredSize().getHeight()+30)));

该行必须插入以下行之后

@Override
        public void actionPerformed(ActionEvent e) {
            textPane1.setText(textPane1.getText() + "\na");
            textPane1.setPreferredSize(new Dimension(150, height));
            textPane2.setText(textPane2.getText() + "\nb");
            textPane2.setPreferredSize(new Dimension(150, height));
            height += 30;

说明：
当您在网格袋布局中设置文本窗格的首选大小时，网格袋布局不会设置其窗格的首选大小，但滚动窗格仅根据其中窗格的首选大小进行滚动。因此，每次更改窗格中组件的大小时，都必须设置窗格的新首选大小，这样滚动窗格将确切地知道他必须做什么。这就是我所做的，添加了一行，增加了creatingPanel的首选大小，这是scrollPanel内部的一行
当其中的组件仅垂直增长时，为什么水平滚动条会自动启用？请包括一个，因为它不清楚你在问什么（至少对我来说）。对不起，我指的是垂直滚动条。@alaster请你用表单中的代码编辑你的帖子，因为这可能是一个教训，为什么JScrollPane不能使用绝对布局，+1来记录这个奇怪的问题。我只使用了GridBagLayout“Done”：对不起，完成了什么？我看到2个SSCCE请求，但没有SSCCE。我只使用GridBagLayout。内部和外部面板。但是当我在附加的SSCCE中使用
GridBagLayout
时，我遇到了同样的问题。这是我的错误。我甚至不需要更改布局。谢谢