confused by 'this' 1

[welldefined]

Hi,

In text1.addActionListener(this); what 'this' for? I remember sometimes 'this' is for the whole class.

 

[kaht]

this references the object that is calling the method - in this instance it is a reference to the object "text1"

-kaht

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[stefanwagner]

You have to lookup the javadocs to find out, that text1.addActionListener (something) is expecting an ActionListener as Argument.

Then you look how an ActionListener is defined.

Well - it is defined as interface, which offers a method 'public void actionPerformed (ActionEvent ae)'.

Now you validate that 'this' is declared to implement an ActionListener, and look for that implementation.
That method is in general what is published by 'this'.

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[welldefined]

kaht,

Thank you. Why your explanation looks not the same as stefanwagner? Perhaps I misunderstood something?

 

[welldefined]

stefanwagner,

Thank you. Did you mean this refers to ActionListener?

 

[sedj]

Kaht,
Sorry, your explanation is not correct.

'this' does not refer to 'text1' in the poster's example.

'this' refers to the object instance of your class.

Often, Swing classes will implement ActionLister, and register themselves as the class listening for events (as per the example).

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[welldefined]

sedj,

Thank you.

Can I use some instance object of another class to replace 'this' in text1.addActionListener(this);

 

[h0h0h0]

Yes, the class you place in there has to implement ActionListener.

 

[welldefined]

h0h0h0,

Thank you. Can you show me any example?

 

[sedj]

Define two classes :

public class MyListener implements ActionListener {
   public void actionPerformed(ActionEvent e) {
      //stuff
   }
}

public class SwingClass {

...
MyListener l = new MyListener();
text1.addActionListener(l);
}
[/code]

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[welldefined]

Thanks a lot.
I think I understand method addActionListener() now!