Question

我试图编译它并且它不断吐出6个错误，说明error:call to super must be first statement in constructor - 我真的很困惑并且无法纠正它。帮助将不胜感激。

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.*;

public class MenuFrame extends JFrame
{
private class ItemHandler
    implements ActionListener
{

    public void actionPerformed(ActionEvent actionevent)
    {
        if(fieldItems[0].isSelected())
            application.insert(textArea);
        else
        if(fieldItems[1].isSelected())
            application.delete(textArea);
        if(fieldItems[2].isSelected())
            application.update(textArea);
        repaint();
    }

    final MenuFrame this$0;

    private ItemHandler()
    {
        this$0 = MenuFrame.this;
        super();
    }

}
     public MenuFrame()
{
    super("Using JMenus");
    JMenu jmenu = new JMenu("File");
    jmenu.setMnemonic('F');
    JMenuItem jmenuitem = new JMenuItem("New");
    jmenuitem.setMnemonic('N');
    jmenu.add(jmenuitem);
    jmenuitem.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent actionevent)
        {
            File file = getFile(2);
            JOptionPane.showMessageDialog(MenuFrame.this, file.toString(), file.toString(), -1);
            application = new HardwareStore(file.toString(), 0);
        }

        final MenuFrame this$0;


        {
            this$0 = MenuFrame.this;
            super();
        }
    }
);
    JMenuItem jmenuitem1 = new JMenuItem("Open");
    jmenuitem1.setMnemonic('O');
    jmenu.add(jmenuitem1);
    jmenuitem1.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent actionevent)
        {
            File file = getFile(1);
            if(file.exists())
            {
                JOptionPane.showMessageDialog(MenuFrame.this, file.toString(), file.toString(), -1);
                application = new HardwareStore(file.toString(), 1);
            }
        }

        final MenuFrame this$0;
 {
            this$0 = MenuFrame.this;
            super();
        }
    }
 );
    jmenu.addSeparator();
    JMenuItem jmenuitem2 = new JMenuItem("Exit");
    jmenuitem2.setMnemonic('x');
    jmenu.add(jmenuitem2);
    jmenuitem2.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent actionevent)
        {
            System.exit(0);
        }

        final MenuFrame this$0;


        {
            this$0 = MenuFrame.this;
            super();
        }
    }
);
    JMenuBar jmenubar = new JMenuBar();
    setJMenuBar(jmenubar);
    jmenubar.add(jmenu);
    JMenu jmenu1 = new JMenu("Process");
    jmenu1.setMnemonic('P');
    String as[] = {
        "Insert", "Delete", "Update"
    };
    JMenu jmenu2 = new JMenu("Edit");
    jmenu2.setMnemonic('E');
    fieldItems = new JRadioButtonMenuItem[as.length];
    fieldButtonGroup = new ButtonGroup();
    ItemHandler itemhandler = new ItemHandler();
    for(int i = 0; i < as.length; i++)
    {
        fieldItems[i] = new JRadioButtonMenuItem(as[i]);
        jmenu2.add(fieldItems[i]);
        fieldButtonGroup.add(fieldItems[i]);
        fieldItems[i].addActionListener(itemhandler);
    }
fieldItems[0].setSelected(true);
    jmenu1.add(jmenu2);
    jmenu1.addSeparator();
    JMenuItem jmenuitem3 = new JMenuItem("List");
    jmenuitem3.setMnemonic('L');
    jmenu1.add(jmenuitem3);
    jmenuitem3.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent actionevent)
        {
            application.display(textArea);
        }

        final MenuFrame this$0;


        {
            this$0 = MenuFrame.this;
            super();
        }
    }
    );
jmenubar.add(jmenu1);
    JMenuItem jmenuitem4 = new JMenuItem("About...");
    jmenuitem4.setMnemonic('A');
    jmenubar.add(jmenuitem4);
    jmenuitem4.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent actionevent)
        {
            JOptionPane.showMessageDialog(MenuFrame.this, "This is an example\nof using menus", "About", -1);
        }

        final MenuFrame this$0;


        {
            this$0 = MenuFrame.this;
            super();
        }
    }
);
    textArea = new JTextArea();
    add(textArea, "Center");
}
private File getFile(int i)
{
    JFileChooser jfilechooser = new JFileChooser();
    jfilechooser.setFileSelectionMode(0);
    int j;
    if(i == 1)
        j = jfilechooser.showOpenDialog(this);
    else
        j = jfilechooser.showSaveDialog(this);
    if(j == 1)
        System.exit(1);
    File file = jfilechooser.getSelectedFile();
    if(file == null || file.getName().equals(""))
    {
        JOptionPane.showMessageDialog(this, "Invalid File Name", "Invalid File Name", 0);
        System.exit(1);
    }
    return file;
}
private JRadioButtonMenuItem fieldItems[];
private JRadioButtonMenuItem fonts[];
private JCheckBoxMenuItem styleItems[];
private JTextArea textArea;
private JTextField recNumText;
private JTextField newValueText;
private JTextField fieldText;
private ButtonGroup fontButtonGroup;
private ButtonGroup fieldButtonGroup;
private int style;
private HardwareStore application;

}

Answer 1

错误很明显。

将其更改为：

private ItemHandler()
{
    super(); // call to super must be the first line of the constructor
    this$0 = MenuFrame.this;
}

对于实例初始化程序块中对super的调用，此类初始化程序块被复制到每个构造函数的开头，因此您必须进行相同的更改：

    {
        super();
        this$0 = MenuFrame.this;
    }

但是，如果具有此类块的类已经有一个调用super（）的构造函数，则不会传递编译。

Answer 2

所有匿名内部类似乎都包含生成的代码，就好像你反编译了一个现有的类文件（我怀疑你有）。每次你有这样的事情：

jmenuitem1.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent actionevent)
    {
        File file = getFile(1);
        if(file.exists())
        {
            JOptionPane.showMessageDialog(MenuFrame.this, file.toString(), file.toString(), -1);
            application = new HardwareStore(file.toString(), 1);
        }
    }

    final MenuFrame this$0;
    {
        this$0 = MenuFrame.this;
        super();
    }
});

...你应该摆脱最后一部分 - 无论如何它都会自动生成。你只需要：

jmenuitem1.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent actionevent)
    {
        File file = getFile(1);
        if(file.exists())
        {
            JOptionPane.showMessageDialog(MenuFrame.this, file.toString(), file.toString(), -1);
            application = new HardwareStore(file.toString(), 1);
        }
    }
});

（虽然我也会添加@Override注释。）

调用super必须是第一个语句错误

2 个答案: