Question

我遇到了JComboBox弹出窗口的问题。我的JComboBox有一个自动完成实现，如谷歌搜索框。

所以，问题是如果我在弹出窗口可见时添加或删除项目它没有调整大小，我需要关闭并重新打开它。但是这个火焰弹出成为不可见和弹出的结果，因此我不能将这个事件用于我的真正的porpouse。

有一种方法可以根据其中包含的项目数量“刷新”弹出窗口大小，而不关闭并重新打开它？

感谢。

Answer 1

在包含组合框的面板上调用revalidate（）。这将导致组件根据其首选尺寸再次布置。

这与在可见GUI上添加/删除组件的概念相同。

编辑：

重新阅读您的问题。我不确定您是否可以在弹出窗口打开时动态调整其大小，但您可以查看Combo Box Popup。它向您展示了如何覆盖弹出窗口的首选宽度。当即将显示弹出菜单时执行此代码。但您可以使用这些概念来访问弹出窗口并动态更改宽度。

编辑2：

这是一个显示基本概念的示例。弹出窗口将每2秒调整一次宽度。但是，我不知道这是否有助于解决您的问题，因为如果您动态添加/删除弹出窗口中的项目，则每次更改弹出窗口时都需要重新创建弹出窗口。这可能会导致弹出窗口隐藏/显示，这意味着无论如何你都需要有一点点闪烁。

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

public class ComboBoxExample extends JPanel implements ActionListener
{
    private JComboBox comboBox;

    public ComboBoxExample()
    {
        String[] petStrings = { "Select Pet", "Bird", "Cat", "Dog", "Rabbit", "Pig", "Other" };
        comboBox = new JComboBox( petStrings );
        add( comboBox, BorderLayout.PAGE_START );

        Timer timer = new javax.swing.Timer(2000, this);
        timer.start();
    }

    public void actionPerformed(ActionEvent e)
    {
        comboBox.showPopup();
        Object child = comboBox.getAccessibleContext().getAccessibleChild(0);
        BasicComboPopup popup = (BasicComboPopup)child;
        JList list = popup.getList();
        Container c = SwingUtilities.getAncestorOfClass(JScrollPane.class, list);
        JScrollPane scrollPane = (JScrollPane)c;

        Dimension size = scrollPane.getSize();

        if (size.width > 20)
            size.width -= 5;

        scrollPane.setPreferredSize(size);
        scrollPane.setMaximumSize(size);

        Dimension popupSize = popup.getSize();
        popupSize.width = size.width;
        Component parent = popup.getParent();
        parent.setSize(popupSize);

        parent.validate();
        parent.repaint();

        Window mainFrame = SwingUtilities.windowForComponent(comboBox);
        Window popupWindow = SwingUtilities.windowForComponent(popup);

        //  For heavy weight popups you need to pack the window

        if (popupWindow != mainFrame)
            popupWindow.pack();
    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame( "ComboBoxExample" );
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        JComponent newContentPane = new ComboBoxExample();
        newContentPane.setOpaque( true );
        frame.setContentPane( newContentPane );
        frame.pack();
        frame.setVisible(true);
    }

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

Answer 2

这是另一个在添加项目时更改宽度的示例：

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

public class ComboBoxExample2 extends JPanel implements ActionListener
{
    private JComboBox comboBox;

    public ComboBoxExample2()
    {
        String[] petStrings = { "A" };
        comboBox = new JComboBox( petStrings );
        comboBox.setPrototypeDisplayValue("A1111111111");
        add( comboBox, BorderLayout.PAGE_START );

        Timer timer = new javax.swing.Timer(2000, this);
        timer.start();
    }

    public void actionPerformed(ActionEvent e)
    {
        String text = comboBox.getItemAt( comboBox.getItemCount() - 1 ).toString();
        comboBox.addItem( text + "1");
        comboBox.showPopup();

        Object child = comboBox.getAccessibleContext().getAccessibleChild(0);
        BasicComboPopup popup = (BasicComboPopup)child;
        JList list = popup.getList();
        Dimension preferred = list.getPreferredSize();
        preferred.width += 20; // allow for scrollbar
        int rowHeight = preferred.height / comboBox.getItemCount();
        int maxHeight = comboBox.getMaximumRowCount() * rowHeight;
        preferred.height = Math.min(preferred.height, maxHeight);

        Container c = SwingUtilities.getAncestorOfClass(JScrollPane.class, list);
        JScrollPane scrollPane = (JScrollPane)c;

        scrollPane.setPreferredSize(preferred);
        scrollPane.setMaximumSize(preferred);

        Dimension popupSize = popup.getSize();
        popupSize.width = preferred.width;
        popupSize.height = preferred.height + 2;
        Component parent = popup.getParent();
        parent.setSize(popupSize);

        parent.validate();
        parent.repaint();

        Window mainFrame = SwingUtilities.windowForComponent(comboBox);
        Window popupWindow = SwingUtilities.windowForComponent(popup);

        //  For heavy weight popups you need to pack the window

        if (popupWindow != mainFrame)
            popupWindow.pack();

    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame( "ComboBoxExample2" );
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        JComponent newContentPane = new ComboBoxExample2();
        newContentPane.setOpaque( true );
        frame.setContentPane( newContentPane );
        frame.pack();
        frame.setVisible(true);
    }

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

如果我在可见时添加项目，则不会调整JComboBox弹出窗口的大小

2 个答案: