java - JScrollPane、JTextArea 和 JPanel 的问题

Question

我需要向我的 JPanel 添加一个垂直滚动条。当长文本字符串没有正确换行等时，问题就出现了。所以我按照在线步骤将它放在文本区域并且它工作正常(没有滚动 Pane )。

然而，在将 JScrollpane(它应该只是垂直的，请假设它是必需的，即不能设置最小尺寸)添加到 JPanel 后，当我水平调整它的大小时，它完全搞砸了。它不会在调整大小时按应有的方式换行，并且其他组件的位置会困惑。

这可能看起来很奇怪，我在这里有不必要的面板，但是我正在作为一个更大的程序的一部分工作并且需要这些面板(for 循环仅用于测试目的)。

总结一下:在水平调整窗口大小时，它的行为与预期不符。

希望得到一些指导。

import java.awt.BorderLayout;
import java.awt.GridLayout;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.ScrollPaneConstants;

public class Main {

    public static void main(String[] args) {

        String s = "Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. ";
        JFrame jf = new JFrame("Test");
        jf.setSize(600, 200);

        JPanel big = new JPanel();
        big.setLayout(new BoxLayout(big, BoxLayout.Y_AXIS));

        for (int i = 0; i < 2; i++) {
            JPanel first = new JPanel(new BorderLayout());

            JPanel insideTop = new JPanel(new GridLayout(2, 2));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));

            JPanel insideMiddle = new JPanel(new BorderLayout());
            insideMiddle.add(new JLabel("Description"), BorderLayout.NORTH);
            JTextArea jta = new JTextArea(s);
            jta.setWrapStyleWord(true);
            jta.setLineWrap(true);
            jta.setEditable(false);
            jta.setFocusable(false);
            jta.setOpaque(false);
            insideMiddle.add(jta, BorderLayout.CENTER);

            JPanel insideBottom = new JPanel(new BorderLayout());
            insideBottom.add(new JLabel("Bottom left"), BorderLayout.WEST);
            insideBottom.add(new JButton("Bottom right"), BorderLayout.EAST);

            first.add(insideTop, BorderLayout.NORTH);
            first.add(insideMiddle, BorderLayout.CENTER);
            first.add(insideBottom, BorderLayout.SOUTH);
            big.add(first);
        }

        JScrollPane scrollPane = new JScrollPane(big, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        jf.add(scrollPane);
        jf.setVisible(true);

    }
}

Answer 1

部分问题是，一旦允许组件扩展，它就不想收缩，因此您需要一些方法来限制组件始终为可视区域的宽度。

幸运的是，有一种相对简单的方法可以使用 Scrollable 接口(interface)来实现...

public class BigPane extends JPanel implements Scrollable {

    @Override
    public Dimension getPreferredScrollableViewportSize() {
        return new Dimension(200, 200);
    }

    @Override
    public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
        return 128;
    }

    @Override
    public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) {
        return 128;
    }

    @Override
    public boolean getScrollableTracksViewportWidth() {
        return true;
    }

    @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;
    }

}

这基本上是让组件始终遵循 JViewport 的宽度，因此当 JScrollPane/JViewport 执行它们的操作时布局，他们知道将组件的宽度限制为可视区域的宽度。因为我喜欢它以这种方式工作，所以当组件的首选高度小于可视区域时，它也会填充空间，但您可以对此做出自己的决定...

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Rectangle;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JViewport;
import javax.swing.ScrollPaneConstants;
import javax.swing.Scrollable;

public class Main {

    public static void main(String[] args) {

        String s = "Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. Hello my name is test. I am a test. ";
        JFrame jf = new JFrame("Test");
        jf.setSize(600, 200);

        BigPane big = new BigPane();
        big.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        gbc.weightx = 1;
        gbc.fill = GridBagConstraints.BOTH;

        for (int i = 0; i < 2; i++) {
            JPanel first = new JPanel(new BorderLayout());

            JPanel insideTop = new JPanel(new GridLayout(2, 2));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));
            insideTop.add(new JLabel("test"));

            JPanel insideMiddle = new JPanel(new BorderLayout());
            insideMiddle.add(new JLabel("Description"), BorderLayout.NORTH);
            JTextArea jta = new JTextArea(s);
            jta.setWrapStyleWord(true);
            jta.setLineWrap(true);
            jta.setEditable(false);
            jta.setFocusable(false);
            jta.setOpaque(false);
            insideMiddle.add(jta, BorderLayout.CENTER);

            JPanel insideBottom = new JPanel(new BorderLayout());
            insideBottom.add(new JLabel("Bottom left"), BorderLayout.WEST);
            insideBottom.add(new JButton("Bottom right"), BorderLayout.EAST);

            first.add(insideTop, BorderLayout.NORTH);
            first.add(insideMiddle, BorderLayout.CENTER);
            first.add(insideBottom, BorderLayout.SOUTH);
            big.add(first, gbc);
        }

        JScrollPane scrollPane = new JScrollPane(big, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED,
                ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

        jf.add(scrollPane);
        jf.setVisible(true);

    }

    public static class BigPane extends JPanel implements Scrollable {

        @Override
        public Dimension getPreferredScrollableViewportSize() {
            return new Dimension(200, 200);
        }

        @Override
        public int getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction) {
            return 128;
        }

        @Override
        public int getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction) {
            return 128;
        }

        @Override
        public boolean getScrollableTracksViewportWidth() {
            return true;
        }

        @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;
        }

    }
}

我还切换到 GridBagLayout，同样，这是个人选择，您可能会发现 BoxLayout 适合您