"this" pointer in a sublcass

[Sam Takoy]

Hi,

The following code doesn't compile with the error:

"No enclosing instance of the type JPanel is accessible in scope"

but isn't my class a JPanel?

Many thanks in advance!

Sam


import java.awt.event.*;
import javax.swing.JPanel;

public class MyClass extends JPanel {

public class MyMouseLisetener extends MouseAdapter {
public void mouseClicked(MouseEvent e) {
JPanel.this.revalidate();
}
}

}

 

[Thomas Richter]

Hi,

The following code doesn't compile with the error:
>
import java.awt.event.*;
import javax.swing.JPanel;

public class MyClass extends JPanel {

public class MyMouseLisetener extends MouseAdapter {
public void mouseClicked(MouseEvent e) {
JPanel.this.revalidate();
}
}

} >
"No enclosing instance of the type JPanel is accessible in scope"

but isn't my class a JPanel?

No, obviously not - it is a MouseAdapter. "this" always refers to the
class the member function is part of.

So long,
Thomas

 

[Sam Takoy]

No, obviously not - it is a MouseAdapter. "this" always refers to the
class the member function is part of.

So long,
Thomas

Are you guessing or giving an educated answer? My impression (perhaps
false) was that the device I was attempting to use was designed for the
specific purpose of going up to the enclosing class.

 

[Stefan Ram]

JPanel.this.revalidate();

This (no pun intended) should be:

MyClass.this.revalidate();

.

 

[Sam Takoy]

This (no pun intended) should be:

MyClass.this.revalidate();

.

Yup - thank you!

 

[Alessio Stalla]

Are you guessing or giving an educated answer? My impression (perhaps
false) was that the device I was attempting to use was designed for the
specific purpose of going up to the enclosing class.

You have to use MyClass.this, not JPanel.this. The enclosing class is
not JPanel, it's MyClass.

Alessio

 

[Lew]

No, obviously not - it is a MouseAdapter. "this" always refers to the
class the member function is part of.

That is incorrect information. The OP is attempting to use "outer
this", that is, 'this' for the enclosing class. So the 'this' in
question is most emphatically not a 'MouseAdapter', it's a 'MyClass',
as others have already pointed out.

 

[Joshua Cranmer]

but isn't my class a JPanel?

Your class is a subclass of JPanel, but the class JPanel does not
enclose the inner class.

The Name.this syntax requires you to specify the actual class enclosing
it, not a supertype of an enclosing class instance.

 

[Roedy Green]

JPanel.this.revalidate();

that syntax is used with you are an inner class and you are trying to
get at a method in an outer class. In this case, you want the current
class, so just use this.revalidate() or even shorter revalidate().
--
Roedy Green Canadian Mind Products
http://mindprod.com

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