java更改JCombobox的高度

Question

有可能增加JComboBox的高度吗？（不参考弹出菜单）

我试过：

comboBox.setPreferredSize(new Dimension(200, 100));

及

Component[] comp = comboBox.getComponents();
for (int i = 0; i < comp.length; i++) {
    if (comp[i] instanceof JButton) {
        JButton btn = (JButton) comp[i];
        btn.setPreferredSize(new Dimension(200, 100));

    }
}

但运气不好。 然后我试图解决布局管理器的问题：

JPanel panel = new JPanel(new GridBagLayout());
panel.setPreferredSize(new Dimension(100, 100));
GridBagConstraints c = new GridBagConstraints();
c.weighty = 1;
c.fill = GridBagConstraints.VERTICAL;
panel.add(cbox, c);

但这似乎不会改变JComboBox按钮的大小

public class ComboBoxFontChange extends JFrame {

    public ComboBoxFontChange() {

        // CREATE BOX
        JComboBox<String> cbox = new JComboBox<String>();
        cbox.setFont(cbox.getFont().deriveFont(30.0f));

        // TRY CHANGE SIZE: DOSE NOT WORK..
        cbox.setPreferredSize(new Dimension(200, 100));
        cbox.setSize(new Dimension(200, 100));
        cbox.setMinimumSize(new Dimension(200, 100));

        // TRY CHANGE SIZE ON BUTTON INSTEAD: DOSE NOT WORK..
        Component[] comp = cbox.getComponents();
        for (int i = 0; i < comp.length; i++) {
            if (comp[i] instanceof JButton) {
                JButton btn = (JButton) comp[i];
                btn.setPreferredSize(new Dimension(200, 100));
                btn.setSize(new Dimension(200, 100));
                btn.setMinimumSize(new Dimension(200, 100));
            }
        }
        cbox.addItem("Quarter");
        cbox.addItem("Nickel");
        cbox.addItem("Penny");
        JPanel panel = new JPanel();
        panel.add(cbox);

        getContentPane().add(panel);

    }

    public static void main(String[] args) {
        ComboBoxFontChange frame = new ComboBoxFontChange();
        frame.setSize(300, 150);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer 1

看看这个代码。我使用自定义^{}设置可见单元格的首选大小

您可以使用以下代码类CustomComboBox，只需更改JLabel的getPreferredSize的维度

然后为comboBox设置渲染器comboBox.setRenderer(newCustomComboBox());

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.ListCellRenderer;
import javax.swing.SwingUtilities;

public class ComboBoxDemo extends JFrame {

    JComboBox cbo = new JComboBox(new String[] {"Hello, StackOverflow"});

    public ComboBoxDemo(){
        cbo.setRenderer(new CustomComboBox());
        add(cbo, BorderLayout.SOUTH);
        add(new JLabel("Hello"), BorderLayout.CENTER);

        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }

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

    static class CustomComboBox extends JLabel implements ListCellRenderer {

        @Override
        public Component getListCellRendererComponent(
                JList list, 
                Object value, 
                int index, 
                boolean isSelected, 
                boolean cellHasFocus) {

            JLabel label = new JLabel(){
                public Dimension getPreferredSize(){
                    return new Dimension(200, 100);
                }
            };
            label.setText(String.valueOf(value));

            return label;
        }
    }        
}

ListCellRenderer javadoc| JComboBox/ListCellRenderer tutorial

Answer 2

这里：

JPanel panel = new JPanel();
panel.add(cbox);

默认情况下JPanel有一个FlowLayout作为布局管理器，这个不支持组件首选的大小。它只适合使用最小尺寸的组件。正如@alex2410在他的评论中所说，您需要使用适当的Layout manager来管理组件的大小和位置

还可以看看这个主题：Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?