java - JScrollPane 中的 JPanel 中的 JTextComponent

Question

我最近需要在单个 JScrollPane 的视口(viewport) View 中放置几个​​组件，其中有一个 JTextPane。 (如果有兴趣，请参阅详情 here)。
我将所有组件(两个 JPanel 和一个 JTextPane)放在另一个 JPanel 中，这个 JPanel 有一个 BorderLayout LayoutManager，并将该 JPanel 设置为 ScrollPane 的视口(viewport) View 。

我立即注意到的是:
JTextPane 不再根据 JScrollPane 的宽度调整其宽度，即使 JScrollPane 设置为 HORIZONTAL_SCROLLBAR_​​NEVER。相反，它只是最大化其宽度以将整个文本放入一行(“\n”换行符除外)。

下面是两张图片:

它应该是这样的:

现在，我找到了this question here这回答了问题的第一部分。 JPanel需要被子类化，子类需要实现Scrollable。

然而，另一个问题随之而来。 JPanel 内部的 JTextPane 不再支持 JPanel 的 BorderLayout.CENTER。如果文本未填满窗口中的剩余空间，则 JTextPane 将不再自行拉伸(stretch)。

我正在寻找一个解决方案。

我希望有一种可靠的方法让 JTextPane 再次遵循 JPanel 的 BorderLayout 并相应地拉伸(stretch)自身。我不正在寻找一些解决方法，例如将背景设为白色，以便 JTextPane 看起来正在填充框架，而实际上并没有。

下面，我发布了一些代码，您可以在其中尝试不同的配置。

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;
        }
    }

}

在此先感谢您能给我的任何帮助!

Answer 1

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

您基本上希望组件跟踪视口(viewport)的高度(调整自身以匹配)，同时视口(viewport)的高度大于组件的首选高度。当组件的首选高度大于视口(viewport)的高度时，您希望停止跟踪并允许组件“溢出”滚动 Pane ，例如...

@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”是 JTable 和 JList 的工作方式