带有 JPanel 的 Java 滚动 JScrollPane 到底部

Question

我有一个 JScrollPane，里面有一个非常高的 JPanel，它是动态改变的，项目被附加在它的末尾。我想要的是滚动到上述 JScrollPane 的底部，以便新添加的项目在添加时立即可见(它们不是直接附加到滚动 Pane ，而是附加到它的 JPanel，并且是私有(private)对象，所以不能引用。

我怎样才能简单地让滚动 Pane 滚动到最底部？提前致谢!

Answer 1

JComponent.scrollRectToVisible(Rectangle) .在 JPanel 实例上调用它。

例如

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

class ScrollToNewLabel {

    public static void main(String[] args) {
        SwingUtilities.invokeLater( new Runnable() {
            public void run() {
                JPanel gui = new JPanel(new BorderLayout(3,3));
                final JPanel panel = new JPanel(new GridLayout(0,1));
                JScrollPane scroll = new JScrollPane(panel);
                scroll.setPreferredSize(new Dimension(80,100));
                gui.add(scroll, BorderLayout.CENTER);
                JButton addLabel = new JButton("Add Label");
                gui.add(addLabel, BorderLayout.NORTH);
                ActionListener listener = new ActionListener() {
                    int counter = 0;
                    public void actionPerformed(ActionEvent ae) {
                        panel.add(new JLabel("Label " + ++counter));
                        panel.revalidate();
                        int height = (int)panel.getPreferredSize().getHeight();
                        Rectangle rect = new Rectangle(0,height,10,10);
                        panel.scrollRectToVisible(rect);
                    }
                };
                addLabel.addActionListener(listener);
                JOptionPane.showMessageDialog(null, gui);
            }
        });
    }
}

屏幕截图

例如2

这例如基于文森特的 answer , 使用 JScrollPane.getVerticalScrollBar() . setValue(height) .其中 height 是面板的首选高度(以像素为单位)。

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

class ScrollToNewLabel {

    public static void main(String[] args) {
        SwingUtilities.invokeLater( new Runnable() {
            public void run() {
                JPanel gui = new JPanel(new BorderLayout(3,3));
                final JPanel panel = new JPanel(new GridLayout(0,1));
                final JScrollPane scroll = new JScrollPane(panel);
                scroll.setPreferredSize(new Dimension(80,100));
                gui.add(scroll, BorderLayout.CENTER);
                JButton addLabel = new JButton("Add Label");
                gui.add(addLabel, BorderLayout.NORTH);
                ActionListener listener = new ActionListener() {
                    int counter = 0;
                    public void actionPerformed(ActionEvent ae) {
                        panel.add(new JLabel("Label " + ++counter));
                        panel.revalidate();
                        int height = (int)panel.getPreferredSize().getHeight();
                        scroll.getVerticalScrollBar().setValue(height);
                    }
                };
                addLabel.addActionListener(listener);
                JOptionPane.showMessageDialog(null, gui);
            }
        });
    }
}