JScrollPane内部的JPanel内部的JTextComponent

Question

我最近需要在一个JScrollPane的viewport视图中放置几个组件，其中包括一个JTextPane。
我将所有组件（两个JPanel和JTextPane）放在另一个JPanel中，这个JPanel有一个BorderLayout LayoutManager，并将该JPanel设置为ScrollPane的viewport视图。

我立即注意到:
JTextPane不再根据JScrollPane的宽度调整其宽度大小，即使JScrollPane设置为horizontal_scrollbar_never也是如此。相反，它只是最大化它的宽度，以将里面的整个文本放入一行（除了“\n”换行符）。

下面是它的两张图片:

它应该是这样的:

现在，我在这里找到了这个问题，它回答了问题的第一部分。JPanel需要子类化，子类需要实现Scrollable。

但是，这样做又产生了另一个问题。JPanel内部的JTextPane不再支持JPanel的BorderLayout.Center。如果文本没有填满窗口中的剩余空间，则JTextPane将不再伸缩。

下面，我发布了一些代码，您可以在那里尝试不同的配置。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.GridLayout;
import java.awt.Rectangle;
import javax.swing.JLabel;
import javax.swing.JTextPane;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;
import javax.swing.Scrollable;


public class MinimalExample extends JFrame {

    private JPanel contentPane;
    private JPanel outerPanel;
    private JPanel firstHeadlinePanel;
    private JLabel lblSomeJlabel;
    private JPanel secondHeadlinePanel;
    private JLabel lblAnotherJlabel;
    private JPanel headlinesPanel;
    private JTextPane textPane;
    private JScrollPane scrollPane;

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {

            public void run() {

                try {
                    MinimalExample frame = new MinimalExample();
                    frame.setVisible(true);
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public MinimalExample() {

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 230, 350);
        contentPane = new JPanel();
        contentPane.setBorder(null);
        setContentPane(contentPane);
        contentPane.setLayout(new GridLayout(1, 0, 0, 0));

        outerPanel = new ScrollablePanel();
        //outerPanel = new JPanel();
        outerPanel.setLayout(new BorderLayout(0, 0));

        headlinesPanel = new JPanel();
        headlinesPanel.setBorder(new EmptyBorder(5, 0, 0, 0));
        outerPanel.add(headlinesPanel, BorderLayout.NORTH);
        headlinesPanel.setLayout(new BorderLayout(0, 0));

        firstHeadlinePanel = new JPanel();
        firstHeadlinePanel.setBorder(new EmptyBorder(0, 0, 5, 0));
        headlinesPanel.add(firstHeadlinePanel, BorderLayout.NORTH);
        firstHeadlinePanel.setLayout(new BorderLayout(0, 0));

        lblSomeJlabel = new JLabel("Some JLabel");
        firstHeadlinePanel.add(lblSomeJlabel, BorderLayout.CENTER);

        secondHeadlinePanel = new JPanel();
        headlinesPanel.add(secondHeadlinePanel, BorderLayout.SOUTH);
        secondHeadlinePanel.setLayout(new BorderLayout(0, 0));

        lblAnotherJlabel = new JLabel("Another JLabel");
        lblAnotherJlabel.setBorder(new EmptyBorder(0, 0, 5, 0));
        secondHeadlinePanel.add(lblAnotherJlabel, BorderLayout.NORTH);

        textPane = new JTextPane();
        textPane.setText(addSomeShortText());
        //textPane.setText(addSomeLongText());
        outerPanel.add(textPane);

        scrollPane = new JScrollPane();
        scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        scrollPane.setViewportView(outerPanel);

        contentPane.add(scrollPane);
    }

    private String addSomeShortText() {

        return ("Lorem ipsum dolor sit amet, consectetur adipiscing elit. Curabitur facilisis "
                + "dictum ullamcorper. Nulla sed diam sit amet ante pellentesque ultricies in non "
                + "est.");
    }

    private String addSomeLongText() {

        return (" Lorem ipsum dolor sit amet, consectetur adipiscing elit. Curabitur facilisis "
                + "dictum ullamcorper. Nulla sed diam sit amet ante pellentesque ultricies in non "
                + "est. Suspendisse sit amet leo purus. Aenean lacinia ornare quam, a porttitor "
                + "tortor vulputate quis. Quisque suscipit porttitor nisl, mollis suscipit ligula "
                + "laoreet vitae. Nulla quis faucibus dui. Donec vestibulum quam sit amet "
                + "facilisis scelerisque. Pellentesque eu lacus eget nibh elementum venenatis in "
                + "congue magna. Donec et vestibulum magna, ut dapibus sapien.\n"
                + "Donec nec enim magna. Curabitur vitae est est. Etiam non tellus nec ipsum "
                + "dapibus ultricies eget ac lacus. Aliquam eu rhoncus leo. Suspendisse sodales "
                + "nibh eros, vel placerat velit bibendum ut. Vivamus feugiat purus at viverra "
                + "volutpat. Donec tincidunt quam quam, ut mattis enim rutrum sit amet. Integer "
                + "volutpat sit amet metus vitae elementum. Aenean ullamcorper iaculis vulputate. "
                + "Etiam venenatis mollis arcu quis interdum. Quisque et pharetra justo, et "
                + "ullamcorper augue. Phasellus id pellentesque massa. Proin suscipit, mauris et "
                + "congue commodo, mi eros fermentum ante, vel ultricies nisl neque a sem. Mauris "
                + "tristique quis erat vel pulvinar. ");
    }

    /* Original source of this is here:
     * https://stackoverflow.com/questions/15783014/jtextarea-on-jpanel-inside-jscrollpane-does-not-resize-properly */
    private static class ScrollablePanel extends JPanel implements Scrollable {

        @Override
        public Dimension getPreferredScrollableViewportSize() {

            return super.getPreferredSize();
        }

        @Override
        public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation,
                int direction) {

            return 16;
        }

        @Override
        public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation,
                int direction) {

            return 16;
        }

        @Override
        public boolean getScrollableTracksViewportWidth() {

            return true;
        }

        @Override
        public boolean getScrollableTracksViewportHeight() {

            return false;
        }
    }

}

谢谢你能给我的任何帮助！

Answer 1

好的，基本上，您需要根据JViewPort和组件的高度更改GetScrollableTracksViewPortHight的工作方式。

当视口的高度大于组件的首选高度时，您基本上希望组件跟踪视口的高度（调整自身以匹配）。当组件的首选高度大于视口的高度时，您希望停止跟踪并允许组件“过度填充”滚动窗格，类似于...

@Override
public boolean getScrollableTracksViewportHeight() {

    boolean track = true;
    Container parent = getParent();
    if (parent instanceof JViewport) {

        JViewport viewport = (JViewport) parent;
        if (viewport.getHeight() < getPreferredSize().height) {
            track = false;
        }

    }

    return track;
}

这“基本上”就是JTable和JList这样的东西的工作方式