Question

我在这里要做的是每次按下按钮并选择图像标签的文本会更改为该图像的路径。

这是我的代码：

public Frame() {
    setAlwaysOnTop(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setBounds(100, 100, 640, 480);
    contentPane = new JPanel();
    contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
    setContentPane(contentPane);
    contentPane.setLayout(null);

    JButton btnNewButton = new JButton("Select image");
    btnNewButton.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) 
        {
            FileNameExtensionFilter filter = new FileNameExtensionFilter("Image", "jpg", "jpeg");
            final JFileChooser fc = new JFileChooser();
            filec.setAcceptAllFileFilterUsed(false);
            filec.addChoosableFileFilter(filter);
            filecc.showDialog(Frame.this, "Select an image");
            File pathh = fc.getSelectedFile();
            String pathhs;
            pathhs = pathh.getPath();
            System.out.println("The path is: " + pathhs);   
            lblNewLabel.setText(pathhs) <--the problem 

        }
    });
    btnNewButton.setBounds(25, 408, 165, 23);
    contentPane.add(btnNewButton);


    JLabel lblNewLabel = new JLabel("New label");
    lblNewLabel.setForeground(Color.BLACK);
    lblNewLabel.setBackground(Color.BLUE);
    lblNewLabel.setBounds(10, 68, 266, 234);
    contentPane.add(lblNewLabel);       
}

问题在于：

                String pathhs;
                pathhs = pathh.getPath();
                System.out.println("The path is: " + pathhs);   
                lblNewLabel.setText(pathhs) <--the problem

我无法访问变量lblNewLabel，因此我无法更改文本。

Answer 1

您可以从匿名类引用局部变量，只要在定义匿名类之前使用final修饰符声明它们。

因此，我会将您的代码修改为：

JButton btnNewButton = new JButton("Select image");
btnNewButton.setBounds(25, 408, 165, 23);
contentPane.add(btnNewButton);


final JLabel lblNewLabel = new JLabel("New label");
btnNewButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent arg0) 
    {
        // Your actionPerformed implementation...
    }
});

lblNewLabel.setForeground(Color.BLACK);
lblNewLabel.setBackground(Color.BLUE);
lblNewLabel.setBounds(10, 68, 266, 234);
contentPane.add(lblNewLabel);

Answer 2

我无法访问变量lblNewLabel，因此我无法更改文本。

将标签定义为类变量而不是局部变量，然后匿名内部类可以访问变量。

更改在ActionListener之后声明的标签文本

2 个答案: