如何从匿名类中访问封闭的类实例变量？

Question

How do I access instance variables from inside the anonymous class's method ?

class Tester extends JFrame {

   private JButton button;
   private JLabel label;
   //..some more

   public Tester() {
        function(); // CALL FUNCTION
   }

   public void function() {
      Runnable r = new Runnable() {
         @Override
         public void run() {
            // How do I access button and label from here ?
         }
      };
      new Thread(r).start();
   }
}

Answer 1

What you are looking for is a fully qualified address since they are not marked final

final Runnable r = new Runnable() {
public void run() {
    Tester.this.button // access what you need
    Tester.this.label  // access what you need
}};

You use the same access pattern for Anonymous Inner Classes when building ActionListeners and other things as well.

This is explained in the specifications as 15.8.4 Qualified this , something the down voter apparently hasn't read. And didn't read the code for comprehension either.

Answer 2

the following code may explain you the format is IncloseingClassName.this.VariableName;

class Tester extends JFrame {
int abc=44;//class variable with collision in name
int xyz=4 ;//class variable without collision in name
public Tester() {
function(); // CALL FUNCTION  
}
public void function() {
Runnable r = new Runnable() {
int abc=55;//anonymous class variable
     @Override
     public void run() {
      System.out.println(this.abc);  //output is 55        
      System.out.println(abc);//output is 55 
      System.out.println(Tester.this.abc);//output is 44 
      //System.out.println(this.xyz);//this will give error
      System.out.println(Tester.this.xyz);//output is 4 
      System.out.println(xyz);//output is 4 
            //output is 4 if variable is declared in only enclosing method 
            //then there is no need of Tester.this.abcd ie you can directly 
            //use the variable name if there is no duplication 
            //ie two variables with same name hope you understood :)

     }
  };
  new Thread(r).start();
   }  }

Answer 3

How do I access instance variables from inside the anonymous class's method ?

You simply access them if need be:

class Tester extends JFrame {

   private JButton button;
   private JLabel label;
   //..some more

   public Tester() {
        function(); // CALL FUNCTION
   }

   public void function() {
      Runnable r = new Runnable() {
         @Override
         public void run() {
            System.out.println("Button's text is: " + button.getText());
         }
      };
      new Thread(r).start();
   }
}

More important: Why isn't this working for you?