java - 我可以使用添加到 JToolBar 的 JButton 来上下滚动 JPanel 吗？

Question

我可以使用添加到 JToolBar 的 JButton 来滚动 JPanel 吗？当我生成大量缩略图时，它们并不全部适合 JPanel。我想使用向上/向下箭头 JButton 进行滚动。这可以做到吗？如果可以，如何做到？

注意:我尝试在没有 JScrollPane 的情况下执行此操作，因为我想要自定义箭头图标，而不是标准滚动条。

这是一个 SSCCE:

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.LineBorder;

public class PicSlider2 {
    private JButton thumbs;
    private JButton[] thumbnails;
    private JLabel picViewer;
    private JPanel thumbPanel;
    private JToolBar toolBar;

public PicSlider2() {
    final JFrame frame = new JFrame("Picture Slider");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setPreferredSize(new Dimension(800, 600));
    frame.setResizable(false);
    frame.setLayout(new BorderLayout());

    picViewer = new JLabel();
    picViewer.setText("Image here");
    picViewer.setHorizontalAlignment(JLabel.CENTER);
    picViewer.setVerticalAlignment(JLabel.BOTTOM);
    picViewer.setBorder(new LineBorder(Color.BLACK, 2));

    JMenuBar frameMenuBar = new JMenuBar();
    frame.setJMenuBar(frameMenuBar);
    JMenu file = new JMenu("File");
    frameMenuBar.add(file);

    JMenuBar picViewerMenu = new JMenuBar();
    picViewerMenu.setLayout(new FlowLayout(FlowLayout.LEFT));
    thumbs = new JButton("THUMBNAILS");//an icon in actual program
    thumbs.setPreferredSize(new Dimension(150,45));
    thumbs.setToolTipText("Thumbnails");
    thumbs.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent evt) {
                picViewer.setVisible(false);
                thumbPanel = new JPanel(new FlowLayout(FlowLayout.CENTER, 20,20));                
                thumbPanel.setBorder(BorderFactory.createEmptyBorder(50,100,50,30));

                thumbnails = new JButton[30];//example size, chosen so all buttons won't fit on one page
                for (int i = 0; i < 30; i++) {
                    thumbnails[i] = new JButton(Integer.toString(i));
                    thumbnails[i].setPreferredSize(new Dimension(100, 100));                  
                    thumbnails[i].addActionListener(new ActionListener() {
                            @Override
                            public void actionPerformed(ActionEvent evt) {                           
                                System.out.println("thumbnail clicked - opens full-size view of pic in the JLabel picViewer");                                  
                            }
                        }); 
                    thumbPanel.add(thumbnails[i]);
                    thumbPanel.setVisible(true); 
                }
                toolBar = new JToolBar(null, JToolBar.VERTICAL);
                toolBar.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 30));
                JButton up = new JButton("Up Arrow");
                up.setPreferredSize(new Dimension(80,60));
                up.addActionListener(new ActionListener() {
                        @Override
                        public void actionPerformed(ActionEvent evt) {  
                            System.out.println("Up Arrow Stub - NEEDS TO SCROLL UP PAGE, as needed");
                        }
                    } );
                JButton down = new JButton("Down Arrow");
                down.setPreferredSize(new Dimension(80,60));
                down.addActionListener(new ActionListener() {
                        @Override
                        public void actionPerformed(ActionEvent evt) {  
                            System.out.println("Down Arrow Stub - NEEDS TO SCROLL DOWN PAGE, as needed");
                        }
                    } );
                toolBar.add(Box.createGlue());
                toolBar.add(up);
                toolBar.add(Box.createVerticalStrut(40));
                toolBar.add(down);
                toolBar.add(Box.createGlue());
                frame.getContentPane().add(thumbPanel, BorderLayout.CENTER);
                frame.getContentPane().add(toolBar, BorderLayout.LINE_END);
            }
        });
    picViewerMenu.add(thumbs);
    frame.getContentPane().add(picViewerMenu, BorderLayout.SOUTH);
    frame.add(picViewer, BorderLayout.CENTER);
    frame.setLocation(300, 50);
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                PicSlider2 ps = new PicSlider2();
            }
        });
}

}

Answer 1

I am trying to do this without a JScrollPane because I want the custom arrow icons

您可以使用 JScrollPane 并使用默认滚动 Action 来创建带有自定义 Icon 的按钮:

import java.awt.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;

public class ScrollPaneSSCCE extends JPanel
{
    public ScrollPaneSSCCE()
    {
        setLayout( new BorderLayout() );
        JTable table = new JTable(50, 5);
        JScrollPane scrollPane = new JScrollPane( table );
        scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER);
        add(scrollPane);
        JScrollBar vertical = scrollPane.getVerticalScrollBar();

        JPanel east = new JPanel( new BorderLayout() );
        add(east, BorderLayout.EAST);

        JButton north = new JButton(  new ActionMapAction("UP", vertical, "negativeUnitIncrement") );
        east.add(north, BorderLayout.NORTH);

        JButton south = new JButton( new ActionMapAction("DOWN", vertical, "positiveUnitIncrement") );
        east.add(south, BorderLayout.SOUTH);
    }

    private static void createAndShowUI()
    {
        JFrame frame = new JFrame("ScrollPaneSSCCE");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new ScrollPaneSSCCE());
        frame.setSize(200, 300);
        frame.setLocationByPlatform( true );
        frame.setVisible( true );
    }

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

您将需要 Action Map Action class，它只是一个简单的包装类，它从指定组件的 ActionMap 获取默认的 Action。

您需要为面板设置滚动增量。由于您的图像大小为 100，您可能需要使用:

vertical.setUnitIncrement( 100 );