在JMenuBar可見后更新JMenu和JMenu字體

Question

下面的代碼創建了一個簡單的GUI，中間有一個按鈕，單擊該按鈕時，應更新JMenuBar組件的字體。 為此，方法setMyFont在JButton上的ActionListener觸發。 然而，經過幾次列出的嘗試，我沒有完成這個，但我不知道為什么。 setMyFont使用的代碼如下

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();
}

有沒有理由不使用當前代碼更新組件上的字體？ 另外，我怎么能改變我的代碼以允許字體在組件上更新，即使它們已經被創建了？

---

SSCCE的完整代碼

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

1. 設置字體后，您需要讓層次結構中的每個組件調用更新它的UI - SwingUtilities有一個方便的方法

    UIManager.put("Menu.font", menuFont); SwingUtilities.updateComponentTreeUI( Main.this ); 

2. 使用FontUIResource類，例如

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

從發布的SSCCE改編的以下代碼適用於我：

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不會處理您添加到框架的菜單欄。

代碼應該是：

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

getComponents（）方法不是遞歸的。 所以你的循環只會將JMenu組件添加到JMenuBar，而不是JMenuItems。

此外，在創建字體時，為什么不使用更大的字體，以便您可以實際查看是否有更改。

同樣在您發布的代碼中，在創建組件之前設置UIManager字體屬性會使按鈕失效。 您的菜單已經是所需的字體。

Answer 3

也許你可以試試這個：

    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);
        }
    }