为什么 JComboBox 忽略 PrototypeDisplayValue [英] Why JComboBox ignore PrototypeDisplayValue

问题描述

关于这两个帖子@iMohammad，使用 JButton 增加/减少 textArea 内的字体大小 和单击 JButton Java 时更改字体样式 ...，我面临着来自 JComboBox 的非常有趣的问题，将 setPrototypeDisplayValue 作为 JComboBox 大小 在屏幕上的参数传递>

请我如何动态调整 JComboBox 的大小取决于 Font，与我在 sscce

import java.awt.*;导入 java.awt.event.*;导入 javax.swing.*;公共类 ComboBoxFontChange 扩展 JFrame {private static final long serialVersionUID = 1L;私人 JComboBox cbox = 新 JComboBox();私有 JTextField tfield = new JTextField("Change");私有 JLabel 标签 = new JLabel("Cash");私有 JButton 按钮 = new JButton("++ 字体");私有 JTextField 文本；私人 JPanel 面板 = 新 JPanel();公共 ComboBoxFontChange() {super("组合框字体更改");text = (JTextField) cbox.getEditor().getEditorComponent();cbox.addItem("更改");cbox.addItem("现金");cbox.addItem("字体");tfield.setColumns(5);button.addActionListener(new ActionListener() {@覆盖public void actionPerformed(ActionEvent e) {字体 font = cbox.getFont();font = font.deriveFont((float) (font.getSize2D() * 1.10));cbox.setFont(字体);//编辑cbox.setPrototypeDisplayValue(cbox.getSelectedItem().toString());tfield.setFont(字体);button.setFont(字体);label.setFont(字体);//panel.revalidate();//panel.repaint();盒();}});//panel.setLayout(new GridLayout(2, 2, 10, 10));panel.add(cbox);panel.add(标签)；panel.add(tfield);面板添加(按钮)；setDefaultCloseOperation(EXIT_ON_CLOSE);添加(面板)；}公共静态无效主(字符串 [] args){SwingUtilities.invokeLater(new Runnable() {@覆盖公共无效运行(){ComboBoxFontChange frame = new ComboBoxFontChange();框架.pack();frame.setVisible(true);}});}}

解决方案

我调试了你的 SSCCE，传递给 setPrototypeDisplayValue 的值是空字符串.将行更改为

cbox.setPrototypeDisplayValue(cbox.getSelectedItem());

使一切按预期工作.删除对 setPrototypDisplayValue 的调用也会使程序按预期运行.

另一个问题是原型显示值没有触发任何事件，因为您像以前一样将其设置为先前的值，并且只有在值实际发生变化时才会触发事件.在 cbox.setPrototypeDisplayValue(cbox.getSelectedItem().toString()) 之前添加 cbox.setPrototypeDisplayValue(""); 使一切都按预期运行，即使在 JDK 1.6 上也是如此.我同意，鉴于字体已更改，应重新计算首选大小，但至少此更改是一种解决方法.

In connections with these two post @iMohammad, Increasing/Decreasing Font Size inside textArea using JButton and Changing Font Style when Clicking on a JButton Java ..., I'm facing with really funny issue that came from JComboBoxby passing setPrototypeDisplayValue as an argument for JComboBox's size on the screen

please how can I resize JComboBox dynamically depends of Font, same as works correctly for another JComponents that I tried in my sscce

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

public class ComboBoxFontChange extends JFrame {

    private static final long serialVersionUID = 1L;
    private JComboBox cbox = new JComboBox();
    private JTextField tfield = new JTextField("Change");
    private JLabel label = new JLabel("Cash");
    private JButton button = new JButton("++ Font");
    private JTextField text;
    private JPanel panel = new JPanel();

    public ComboBoxFontChange() {
        super("Combo Box Font change");
        text = (JTextField) cbox.getEditor().getEditorComponent();
        cbox.addItem("Change");
        cbox.addItem("Cash");
        cbox.addItem("Font");
        tfield.setColumns(5);
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                Font font = cbox.getFont();
                font = font.deriveFont((float) (font.getSize2D() * 1.10));
                cbox.setFont(font);
                // EDIT
                cbox.setPrototypeDisplayValue(cbox.getSelectedItem().toString());
                tfield.setFont(font);
                button.setFont(font);
                label.setFont(font);
                //panel.revalidate();
                //panel.repaint();
                pack();
            }
        });
        //panel.setLayout(new GridLayout(2, 2, 10, 10));
        panel.add(cbox);
        panel.add(label);
        panel.add(tfield);
        panel.add(button);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        add(panel);
    }

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

            @Override
            public void run() {
                ComboBoxFontChange frame = new ComboBoxFontChange();
                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}

解决方案

I debugged your SSCCE, and the value passed to setPrototypeDisplayValue is the empty string. Changing the line to

cbox.setPrototypeDisplayValue(cbox.getSelectedItem());

Makes everything work as expected. Removing the call to setPrototypDisplayValue also makes the program behave as expected.

EDIT:

The other problem is that no event is fired for the prototype display value because you set it to the previous value as before, and an event is only fired if the value actually changes. Adding cbox.setPrototypeDisplayValue(""); before cbox.setPrototypeDisplayValue(cbox.getSelectedItem().toString()) makes everything behave as expected, even on JDK 1.6. I agree that given that the font is changed, the preferred size should be recomputed, but at least this change is a workaround.

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