使用 JFileChooser - 访问所选文件

Question

有一段时间没有写代码了，所以我觉得我有点生疏了。我正在尝试构建一个应用程序，让用户选择一个文件作为输入。以下代码是我目前所拥有的：

JButton btnFile = new JButton("Select Excel File");
btnFile.addActionListener(new ActionListener() {
    //Handle open button action.
    public void actionPerformed(ActionEvent e) {
        final JFileChooser fc = new JFileChooser(); 
        int returnVal = fc.showOpenDialog(frmRenamePdfs);
        if (returnVal == JFileChooser.APPROVE_OPTION) {
            File file = fc.getSelectedFile();
            //This is where a real application would open the file.
            System.out.println("File: " + file.getName() + ".");    
        } else {
            System.out.println("Open command cancelled by user.");
        }
        System.out.println(returnVal);
    }
});

我似乎无法弄清楚如何从侦听器外部访问“文件”，即在创建 GUI 其余部分的函数中。我在启动文件选择器的按钮旁边有一个空白文本标签，所以我想要做的是存储文件，并将文本标签的文本设置为文件名。

Answer 1

File file在类级别而不是在匿名内部类中定义变量怎么样？

public class SwingSandbox {

  private File file;

  public SwingSandbox() {
    final JFrame frame = new JFrame("Hello");

    JButton btnFile = new JButton("Select Excel File");
    btnFile.addActionListener(new ActionListener() {
        //Handle open button action.
        public void actionPerformed(ActionEvent e) {
            final JFileChooser fc = new JFileChooser(); 
            int returnVal = fc.showOpenDialog(frame);
            if (returnVal == JFileChooser.APPROVE_OPTION) {
                file = fc.getSelectedFile();
                //This is where a real application would open the file.
                System.out.println("File: " + file.getName() + ".");    
            } else {
                System.out.println("Open command cancelled by user.");
            }
            System.out.println(returnVal);
        }
    });

    frame.getContentPane().add(btnFile);
    frame.setSize(100, 100);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
  }


  public static void main(String[] args) throws Exception {
    new SwingSandbox();
  }

}