Calling a class within another class

[BeeGee]

Hi, thanks for pointing that out. I know that but I was changing the names before I posted it on here as a result of my earlier concerns as stated in my first message.

[BeeGee]

 
package one;

import java.awt.*;


import javax.swing.*;

public class AnotherGUI extends JFrame {
	
	private JLabel nameLabel;
	
	private JLabel genderLabel;
	
	private JTextField nametextField;
	
	private JTextField gendertextField;
	
	
	public AnotherGUI(Login login){
		super(login.getUserName());
		Container pane = getContentPane();
		pane.setLayout(new FlowLayout());
		
		
		Font monospacedFont = new Font("Monospaced", Font.PLAIN, 14);
		
		//Instantiates Labels, TextFields and Buttons
		nameLabel = new JLabel("Name: ");
		nameLabel.setFont(monospacedFont);
		nametextField = new JTextField(2);
		
		genderLabel = new JLabel ("Gender: ");
		genderLabel.setFont(monospacedFont);
		gendertextField = new JTextField(6);
		
		
		
		//Adds the labels, textFields, and buttons to the pane
		pane.add(nameLabel);
		pane.add(nametextField);
		
		pane.add(genderLabel);
		pane.add(gendertextField);
		
		pack();
		setVisible(true);
	}

}

I hope this helps.

[StormyWaters]

So what are the exceptions you are seeing?

[BeeGee]

Exception in thread "AWT-EventQueue-0" java.lang.Error: Unresolved compilation problem:
The constructor AnotherGUI(Login.ButtonHandler) is undefined

at one.Login$ButtonHandler.actionPerformed(Login.java :101)
at javax.swing.AbstractButton.fireActionPerformed(Unk nown Source)
at javax.swing.AbstractButton$Handler.actionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseRe leased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent( Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(U nknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unkno wn Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[Tolls]

Doh!

Silly me. I so rarely use anything other than anonymous classes for listeners that I completely missed that "this" would refer to the ButtonHandler and not the Login.

Either go for an anonymous inner class for the listener (if you know what they are), or pass the Login into the ButtonHandler constructor (which will involve adding a constructor to the ButtonHandler that takes a Login). That'll be stored (as in AnotherGui), which will be passed to AnotherGui instead of "this".

ETA: In case that's a bit too much writing, this is what I mean:

class ButtonHandler blah blah {
    Login login;  // pass this to the AnotherGUi constructor instead of "this".
    ButtonHandler(Login login) {
        this.login = login;
    }
...other stuff...
}

[Tolls]

Double doh!
It's still an inner class isn't it?

Ignore most of my stuff then...:)
Apart from the anonymous listener if you understand them...they make far more sense, to me anyway.

[StormyWaters]

No the doh was all mine lol,

I didn't look to see if it was anonymous or not, lol. I was intrigued by you're reply and I was unsure if just an inner class would work with Login.this, so I tested it and it doesn't.

[Tolls]

Oh...of course...I knew that...oh yes.

I was just testing you all...

*ahem*

[StormyWaters]

Oh wait I screwed up again lol, it does, my bad.

So yeah just use Login.this for the constructor call.

[Tolls]

I'm quite capable of making myself look foolish, you know...
;)

[StormyWaters]

I believe we all are lol

[BeeGee]

I'm sorry I couldn't explain it better.
So where does Login.this go please?

[BeeGee]

I've never used anonymous classes but I'll read about it.

[StormyWaters]

Just switch the constructor call from

new AnotherGUI(this)

to

new AnotherGUI(Login.this)

The reasoning behind this is that the "this" is referring to your ButtonHandler.class. However since the ButtonHandler is inside the Login class, you can specify it to use the Login class by doing Login.this.

[Tolls]

Instead of the "this" passed into the constructor:
new AnotherGUI(this);

pass Login.this.

Because ButtonHandler is an inner class to Login, "this" refers to the ButtonHandler object we're in at the time. To get at the Login object we are a part of, we need to use Login.this.

[Tolls]

Or, to put it another way...what he said...^
:)

[BeeGee]

You guys are the best. Sorry for the trouble and thanks for your help. I will look up anonymous classes. Is that the best thing to use for listeners?

[Tolls]

If your listener is essentially doing one thing on one object (button in this case) then I find it better to assign an anonymous listener to the button which then calls a method in the class itself...unless the action is only a couple of lines.

So:

        JButton jb = new JButton();
        jb.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                handleJBButtonAction();
            }
        });

Where handleJBButtonAction() will do the work. As I say, if the work is only a couple of lines that bit is unecessary. What you don't want to do is stick loads of code in there as it becomes messy really quickly.

This ties the listener code to the button in a (fairly) clear way. As with everything, though, YMMV. If you had a load of listeners on a single object then you may end up with a mess as well.

[Fubarable]

No the doh was all mine lol,

I didn't look to see if it was anonymous or not, lol. I was intrigued by you're reply and I was unsure if just an inner class would work with Login.this, so I tested it and it doesn't.

This looks remarkably like my reply #14 way back on the first page. ;)

[Tolls]

Of right, Mr Clever-Clever...:p

;)