Jcomponents 在本机外观中显示问题

Question

我有一个简单的 GUI，其中包含 JButton、JMenuBar。这在正常情况下工作正常（显示和对齐）但如果我在 UIManager 代码下面使用它不正确，

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

我面临的问题的 SSSCE 发布在下面，

import java.awt.HeadlessException;
import javax.swing.GroupLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class UiManagerEx extends JFrame{
    JMenuBar menuBar;
    JTextField textField;
    JLabel labl;
    JButton btn;

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

    public UiManagerEx() throws HeadlessException {
        init();
    }
    private void init(){
        JPanel panel = new JPanel();

        menuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("Example");
        menuBar.add(fileMenu);

        JMenuItem menuAction = new JMenuItem("ONE");
        fileMenu.add(menuAction);

        JMenuItem menu1Action = new JMenuItem("TWO");
        fileMenu.add(menu1Action);

        labl = new JLabel("Test");
        textField = new JTextField("example Program");
        btn = new JButton("enable");
        btn.setEnabled(false); // Make it true and the text will be visible.

        GroupLayout settingsLayout = new GroupLayout(panel);
        panel.setLayout(settingsLayout);
        settingsLayout.setAutoCreateGaps(true);
        settingsLayout.setAutoCreateContainerGaps(true);
        GroupLayout.SequentialGroup hGroup = settingsLayout.createSequentialGroup();
        hGroup.addGroup(settingsLayout.createParallelGroup()
                .addComponent(labl));
        hGroup.addGap(10);
        hGroup.addGroup(settingsLayout.createParallelGroup()
                .addComponent(textField,GroupLayout.PREFERRED_SIZE, 200, GroupLayout.PREFERRED_SIZE));
        hGroup.addGap(10);
        hGroup.addGroup(settingsLayout.createParallelGroup()
                .addComponent(btn,GroupLayout.PREFERRED_SIZE, 100, GroupLayout.PREFERRED_SIZE));
        hGroup.addGap(10);
        settingsLayout.setHorizontalGroup(hGroup);
        GroupLayout.SequentialGroup vGroup = settingsLayout.createSequentialGroup();
        vGroup.addGap(10);
        vGroup.addGroup(settingsLayout.createParallelGroup(GroupLayout.Alignment.BASELINE)
                .addComponent(labl)
                .addComponent(textField)
                .addComponent(btn));
        vGroup.addGap(10);

        settingsLayout.setVerticalGroup(vGroup);
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); //Comment this to make "alignement of JmenuItem" work properly
        } catch (ClassNotFoundException ex) {}
        catch (InstantiationException ex) {}
        catch (IllegalAccessException ex) {}
        catch (UnsupportedLookAndFeelException ex) {}

        add(panel);
        setJMenuBar(menuBar);
        setTitle("Stack overflow");
        setResizable(true);
        setSize(400, 200);
        setLocationRelativeTo(this);
        setVisible(true);
    }
}

在原生外观中，

1. 如果我设置Jbutton.SetEnabled(false)，Jbutton 的文本（启用）不可见
2. JmenuBar 显示不正确。（单击菜单栏时菜单项未正确对齐）。

在处理这些问题的 java 应用程序中是否有任何方法可以让我获得原生外观。

我是新手..请帮忙！

Answer 1

在创建对象之前设置 LookAndFeel。然后显示按钮文本： 但我无法解释为什么。也许有一些依赖于 LookAndFeel 的初始化

private void init(){
 try {
      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); // Comment this to make
                                                                           // "alignement of JmenuItem" work
                                                                           // properly
    }
    catch (ClassNotFoundException ex) {
      ex.printStackTrace();
    }
    catch (InstantiationException ex) {
      ex.printStackTrace();
    }
    catch (IllegalAccessException ex) {
      ex.printStackTrace();
    }
    catch (UnsupportedLookAndFeelException ex) {
      ex.printStackTrace();
    }
    JPanel panel = new JPanel();