Question

我想找到答案，但我不能。在java中，当我创建一个子类时，我如何才能获得第一级类？使用＆＃34;这个＆＃34;访问子类，所以我不能。另一个选择是将参数传递给子类，但我很好奇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

您有几个选择：

使匿名类之外的变量成为实例变量：

public class AnonymousClass extends JFrame {
    private JLabel label;
    ...

    public AnonymousClass() {
    ...
        btnOk.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                label.setText(textField.getText());
            }
        });
    ...
    }

您还可以按如下方式访问实例变量：

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

在局部变量上使用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final modifier will mean you cannot re-assign the variable at a later point in your program.

如何引用类fromasubclass

2 个答案: