Question

下面的代码创建了一个简单的GUI，中间有一个按钮，单击该按钮时，应更新JMenuBar组件的字体。为此，setMyFont上的ActionListener会触发JButton方法。然而，经过几次列出的尝试，我没有完成这个，但我不知道为什么。 setMyFont中使用的代码位于

之下

public void setMyFont(Font f, Font f2) {
    //Attempt 1 in the hope it would autodetect that font
    //had changed and just update
    menuFont = f;
    menuItemFont = f2;

    //Attempt 2 in the hope on the repaint it would update 
    //the font with the new UIManager properties
    UIManager.put("Menu.font", menuFont);
    UIManager.put("MenuItem.font", menuItemFont);

    //Attempt 3 in the hope that going over each component 
    //individually would update the font
    for(Component comp: getComponents()) {
        if(comp instanceof JMenu) {
            comp.setFont(menuFont);
        } else {
            comp.setFont(menuItemFont);
        }
    }

    validate();
    repaint();
}

是否有理由使用当前代码在组件上更新字体？另外，我怎么能改变我的代码以允许字体在组件上更新，即使它们已经被创建了？

SSCCE的完整代码

import java.awt.Component;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.UIManager;

public class Main extends JFrame {
    private static final long serialVersionUID = 3206847208968227199L;
    JButton but;
    MenuBar mB;

    private Main() {
        setSize(600, 600);

        mB = new MenuBar();
        setJMenuBar(new MenuBar());

        but = new JButton("Change Font");
        but.addActionListener(new CustomActionListener());
        add(but);

        setVisible(true);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        new Main();
    }

    private class MenuBar extends JMenuBar {
        private static final long serialVersionUID = -2055260049565317972L;
        Font menuFont = new Font("Courier", Font.ITALIC + Font.BOLD, 12);
        Font menuItemFont = new Font("sans-serif", 0, 12);
        JMenu menu, subMenu;

        MenuBar() {
            UIManager.put("Menu.font", menuFont);
            UIManager.put("MenuItem.font", menuItemFont);

            menu = new JMenu("Menu");

            subMenu = new JMenu("Sub Menu");
            subMenu.add(new JMenuItem("Sub Item"));
            subMenu.add(new JMenu("Sub Menu"));
            menu.add(subMenu);

            menu.add(new JMenuItem("Sub Item"));
            menu.add(new JMenu("Sub Menu"));

            add(menu);

            menu = new JMenu("Another Menu");
            menu.add(new JMenu("Sub Menu"));
            menu.add(new JMenuItem("Sub Item"));
            menu.add(new JMenu("Sub Menu"));
            add(menu);
        }

        public void setMyFont(Font f, Font f2) {
            //Attempt 1 in the hope it would autodetect that font
            //had changed and just update
            menuFont = f;
            menuItemFont = f2;

            //Attempt 2 in the hope on the repaint it would update 
            //the font with the new UIManager properties
            UIManager.put("Menu.font", menuFont);
            UIManager.put("MenuItem.font", menuItemFont);

            //Attempt 3 in the hope that going over each component 
            //individually would update the font
            for(Component comp: getComponents()) {
                if(comp instanceof JMenu) {
                    comp.setFont(menuFont);
                } else {
                    comp.setFont(menuItemFont);
                }
            }

            validate();
            repaint();
        }
    }

    private class CustomActionListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            mB.setMyFont(new Font("sans-serif", 0, 12), new Font("Courier", Font.ITALIC + Font.BOLD, 12));
        }
    }
}

Answer 1

设置字体后，您需要让层次结构调用中的每个组件更新它的UI - SwingUtilities有一个方便的方法
```
UIManager.put("Menu.font",  menuFont);
SwingUtilities.updateComponentTreeUI( Main.this );
```

使用FontUIResource类，例如

FontUIResource menuFont = new FontUIResource("Courier", Font.ITALIC + Font.BOLD, 12);

以下代码改编自已发布的SSCCE适用于我：

import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.plaf.FontUIResource;

public class Main extends JFrame {
    private static final long serialVersionUID = 3206847208968227199L;
    JButton but;
    MenuBar mB;

    private Main() {
        setSize(600, 600);

        mB = new MenuBar();
        setJMenuBar(mB);

        but = new JButton("Change Font");
        but.addActionListener(new CustomActionListener());
        add(but);

        setVisible(true);
        setLocationRelativeTo(null);
    }

    public static void main(String[] args) {
        new Main();
    }

    private class MenuBar extends JMenuBar {
        private static final long serialVersionUID = -2055260049565317972L;
        Font menuFont = new FontUIResource("Courier", Font.ITALIC + Font.BOLD, 12);
        Font menuItemFont = new FontUIResource("sans-serif", 0, 12);
        JMenu menu, subMenu;

        MenuBar() {
            UIManager.put("Menu.font", menuFont);
            UIManager.put("MenuItem.font", menuItemFont);

            menu = new JMenu("Menu");

            subMenu = new JMenu("Sub Menu");
            subMenu.add(new JMenuItem("Sub Item"));
            subMenu.add(new JMenu("Sub Menu"));
            menu.add(subMenu);

            menu.add(new JMenuItem("Sub Item"));
            menu.add(new JMenu("Sub Menu"));

            add(menu);

            menu = new JMenu("Another Menu");
            menu.add(new JMenu("Sub Menu"));
            menu.add(new JMenuItem("Sub Item"));
            menu.add(new JMenu("Sub Menu"));
            add(menu);
        }

        public void setMyFont(Font f, Font f2) {

            menuFont = f;
            menuItemFont = f2;
            UIManager.put("Menu.font", menuFont);
            UIManager.put("MenuItem.font", menuItemFont);
            SwingUtilities.updateComponentTreeUI(Main.this);
        }
    }

    private class CustomActionListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            mB.setMyFont(new FontUIResource("sans-serif", 0, 12), new FontUIResource("Courier", Font.ITALIC + Font.BOLD, 12));
        }
    }
}

Answer 2

    mB = new MenuBar();
    setJMenuBar(new MenuBar());

您的ActionListener不会处理您添加到框架中的菜单栏。

代码应为：

    mB = new MenuBar();
    //setJMenuBar(new MenuBar());
    setJMenuBar(mB);

getComponents（）方法不是递归的。所以你的循环只会将JMenu组件添加到JMenuBar，而不是JMenuItems。

同样在创建字体时，为什么不使用更大的字体，以便您可以实际查看是否有变化。

同样在您发布的代码中，在创建组件之前设置UIManager字体属性会使按钮失效。您的菜单已经是所需的字体。

Answer 3

也许你可以试试这个：

    public class MenuFontChange {

    public static void changeMenuFont(JMenuBar jBar, Font font) {
        Component[] components = jBar.getComponents();
        for (Component component : components) {
            component.setFont(font);
            changeMenuItemFont((JMenu) component, font);
        }
    }

    public static void changeMenuItemFont(JMenu jMenu, Font font) {
        int n = jMenu.getItemCount();
        for (int i = 0; i < n; i++) {
            JMenuItem item = jMenu.getItem(i);
            item.setFont(font);
        }
    }

JMenuBar可见后更新JMenu和JMenu字体

3 个答案: