如何将非最终变量传递给匿名内部类？

发布于 2024-11-14 22:41:45 字数 815 浏览 3 评论 0原文

我有这些代码行。我知道您不能将非最终变量传递给内部类，但我需要将变量i传递给匿名内部类以用作座位ID。你能建议这样做的方法吗？

JButton [] seats = new JButton [40]; //creating a pointer to the buttonsArray
for (int i = 0; i < 40; i++)
{
    seats[i] = new JButton();//creating the buttons
    seats[i].setPreferredSize(new Dimension(50,25));//button width
    panel4seating.add(seats[i]);//adding the buttons to the panels

    seats[i].addActionListener(new ActionListener()
    {  //anonymous inner class
        public void actionPerformed(ActionEvent evt)
        {  
            String firstName = (String)JOptionPane.showInputDialog("Enter First Name");
            String lastName = (String)JOptionPane.showInputDialog("Enter Last Name");

            sw101.AddPassenger(firstName, lastName, seatingID);
        }
    });
}

原文

I have these lines of code. I know you can not pass a non final variable to an inner class but I need to pass the variable i to the anonymous inner class to be used as a seatingID. Can you suggest ways of doing that ?

JButton [] seats = new JButton [40]; //creating a pointer to the buttonsArray
for (int i = 0; i < 40; i++)
{
    seats[i] = new JButton();//creating the buttons
    seats[i].setPreferredSize(new Dimension(50,25));//button width
    panel4seating.add(seats[i]);//adding the buttons to the panels

    seats[i].addActionListener(new ActionListener()
    {  //anonymous inner class
        public void actionPerformed(ActionEvent evt)
        {  
            String firstName = (String)JOptionPane.showInputDialog("Enter First Name");
            String lastName = (String)JOptionPane.showInputDialog("Enter Last Name");

            sw101.AddPassenger(firstName, lastName, seatingID);
        }
    });
}

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又爬满兰若 2024-11-21 22:41:45

简单的方法是创建一个局部最终变量并使用循环变量的值对其进行初始化；例如

    JButton [] seats = new JButton [40]; //creating a pointer to the buttonsArray
    for (int i = 0; i < 40; i++)
    {
        seats[i] = new JButton();//creating the buttons
        seats[i].setPreferredSize(new Dimension(50,25));//button width
        panel4seating.add(seats[i]);//adding the buttons to the panels
        final int ii = i;  // Create a local final variable ...
        seats[i].addActionListener(new ActionListener()
         {  //anonymous inner class
            public void actionPerformed(ActionEvent evt)
            {  
                String firstName = (String)JOptionPane.showInputDialog("Enter First Name");
                String lastName = (String)JOptionPane.showInputDialog("Enter Last Name");

                sw101.AddPassenger(firstName, lastName, ii);
            }
         });
    }

The simple way is to create a local final variable and initialize it with the value of the loop variable; e.g.

    JButton [] seats = new JButton [40]; //creating a pointer to the buttonsArray
    for (int i = 0; i < 40; i++)
    {
        seats[i] = new JButton();//creating the buttons
        seats[i].setPreferredSize(new Dimension(50,25));//button width
        panel4seating.add(seats[i]);//adding the buttons to the panels
        final int ii = i;  // Create a local final variable ...
        seats[i].addActionListener(new ActionListener()
         {  //anonymous inner class
            public void actionPerformed(ActionEvent evt)
            {  
                String firstName = (String)JOptionPane.showInputDialog("Enter First Name");
                String lastName = (String)JOptionPane.showInputDialog("Enter Last Name");

                sw101.AddPassenger(firstName, lastName, ii);
            }
         });
    }

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我很OK 2024-11-21 22:41:45

您不能直接这样做，但您可以创建 ActionListener 的（静态私有）子类，该子类在其构造函数中采用 SeatingID。

然后，而不是

seats[i].addActionListener(new ActionListener() { ... });

你

seats[i].addActionListener(new MySpecialActionListener(i));

[编辑]实际上，你的代码还有很多其他错误，我不确定这个建议是否好。展示可以编译的代码怎么样？

You can't directly, but you can make a (static private) subclass of ActionListener that takes a seatingID in its constructor.

Then rather than

seats[i].addActionListener(new ActionListener() { ... });

you'd have

seats[i].addActionListener(new MySpecialActionListener(i));

[Edit] Actually, there's so much else wrong with your code that I'm not really sure that this advice is good. How about presenting code that would compile.

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