如果添加了太多按钮，JToolBar 显示箭头

Question

当可见容器小于所有按钮所需的空间时，有没有办法在 JToolBar(API) 中添加箭头（如 ）？

（为便于说明，请参阅WebUI zkoss）

UI 管理器 (L&F) 应该是正常的 swing 管理器。

Answer 1

有没有办法有箭头

它不是 API 的一部分，因此您需要自己创建。

您也许可以使用以下内容为您提供一些想法。当所有按钮没有足够的空间时，此示例将按钮添加到左/右，以便您可以滚动查看每个按钮：

import java.awt.*;
import java.util.List;
import java.util.ArrayList;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;


public class ScrollContainer extends JPanel
    implements ActionListener, ComponentListener
{
    private Container container;
    private List<Component> removedComponents = new ArrayList<Component>();
    private JButton forwardButton;
    private JButton backwardButton;

    public ScrollContainer(Container container)
    {
        this.container = container;
        setLayout( new BorderLayout(5, 0) );
        addComponentListener( this );

        //  Create buttons to control scrolling

        backwardButton = new BasicArrowButton( BasicArrowButton.WEST );
        configureButton( backwardButton );
        forwardButton = new BasicArrowButton( BasicArrowButton.EAST);
        configureButton( forwardButton );

        //  Layout the panel

        add( backwardButton, BorderLayout.WEST );
        add( container );
        add( forwardButton, BorderLayout.EAST );
    }

    //  Implement the ComponentListener

    public void componentResized(ComponentEvent e)
    {
        //  When all components cannot be shown, add the forward button

        int freeSpace = getSize().width - container.getPreferredSize().width;

        if (backwardButton.isVisible())
            freeSpace -= backwardButton.getPreferredSize().width;

        forwardButton.setVisible( freeSpace < 0 );

        //  We have free space, redisplay removed components

        while (freeSpace > 0 && ! removedComponents.isEmpty())
        {
            if (removedComponents.size() == 1)
                freeSpace += backwardButton.getPreferredSize().width;

            Object o = removedComponents.get(removedComponents.size() - 1);
            Component c = (Component)o;
            freeSpace -= c.getSize().width;

            if (freeSpace >= 0)
            {
                container.add(c, 0);
                removedComponents.remove(removedComponents.size() - 1);
            }
        }

        //  Some components still not shown, add the backward button

        backwardButton.setVisible( !removedComponents.isEmpty() );

//      repaint();

    }

    public void componentMoved(ComponentEvent e) {}
    public void componentShown(ComponentEvent e) {}
    public void componentHidden(ComponentEvent e) {}

    //  Implement the ActionListener

    public void actionPerformed(ActionEvent e)
    {
        Object source = e.getSource();

        //  Scroll the components in the container

        if (source == forwardButton)
            scrollForward();
        else
            scrollBackward();
    }

    /*
     *  Simulate scrolling forward
     *  by remove the first component from the container
     */
    private void scrollForward()
    {
        if (container.getComponentCount() == 1)
            return;

        //  Remove and save the first component

        Component c = container.getComponent(0);
        container.remove( c );
        removedComponents.add( c );

        //  Allow for backwards scrolling

        backwardButton.setVisible( true );

        //  All components are showing, hide the forward button

        int backwardButtonWidth = backwardButton.getPreferredSize().width;
        int containerWidth = container.getPreferredSize().width;
        int panelWidth = getSize().width;

        if (backwardButtonWidth + containerWidth <= panelWidth)
            forwardButton.setVisible( false );

        //  Force a repaint of the panel

        revalidate();
        repaint();
    }

    /*
     *  Simulate scrolling backward
     *  by adding a removed component back to the container
     */
    private void scrollBackward()
    {
        if (removedComponents.isEmpty())
            return;

        //  Add a removed component back to the container

        Object o = removedComponents.remove(removedComponents.size() - 1);
        Component c = (Component)o;
        container.add(c, 0);

        //  Display scroll buttons when necessary

        if (removedComponents.isEmpty())
            backwardButton.setVisible( false );

        forwardButton.setVisible( true );
        revalidate();
        repaint();
    }

    private void configureButton(JButton button)
    {
        button.setVisible( false );
        button.addActionListener( this );
    }

    private static void createAndShowGUI()
    {
        JToolBar toolBar = new JToolBar();
        toolBar.setFloatable(false);
        toolBar.add( new JButton("one") );
        toolBar.add( new JButton("two222222") );
        toolBar.add( new JButton("three") );
        toolBar.add( new JButton("four") );
        toolBar.add( new JButton("five") );
        toolBar.add( new JButton("six666666666") );
        toolBar.add( new JButton("seven") );
        toolBar.add( new JButton("eight") );
        toolBar.add( new JButton("nine9999999") );
        toolBar.add( new JButton("ten") );
        ScrollContainer container = new ScrollContainer(toolBar);

        JFrame frame = new JFrame("Scroll Container");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(container, BorderLayout.NORTH);
        frame.setLocationByPlatform( true );
        frame.pack();
        frame.setVisible( true );
    }

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

因此您需要修改代码以根据需要创建一个弹出菜单以包含额外的按钮。