java如何从AsubClass引用类

Question

我试图找到答案，但我找不到。在java中，当我创建一个子类时，如何引用第一级类？使用“this”访问子类，所以我不能。另一个选项是将参数传递给子类，但我想知道是否有最简单的方法

//here there is my other 1st level class implementation, this is a JFrame
btnNewProject.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent arg0) {

            VehicleScreen pp=new VehicleScreen(**here should go the top class reference**);
                //v is a JPanel that I pass to allJframes
                v.setContentPane(pp);
                v.setVisible(true);
        }
    });

Answer 1

class Foo {
  int x;

  Foo() {
    new Runnable() {
      public void run() {
        Foo.this.x = 1;
      }
    }
  }
}

Answer 2

您有两个选择：

1. 将匿名类之外的变量设为实例变量：

   public class AnonymousClass extends JFrame {
       private JLabel label;
       ...
   
       public AnonymousClass() {
       ...
           btnOk.addActionListener(new ActionListener() {
   
               @Override
               public void actionPerformed(ActionEvent e) {
                   label.setText(textField.getText());
               }
           });
       ...
       }
   

   您还可以访问实例变量，如下所示：

   AnonymousClass.this.label.setText(textField.getText());
   

2. 对局部变量使用final修饰符：

   public class AnonymousClass extends JFrame {
       ...
   
       public AnonymousClass() {
       final JLabel label = new JLabel("Enter a new message!");
           btnOk.addActionListener(new ActionListener() {
   
               @Override
               public void actionPerformed(ActionEvent e) {
                   label.setText(textField.getText());
               }
           });
       ...
       }
   

   请注意，使用^{} modifier will mean you cannot re-assign the variable at a later point in your program.