? member access

[Geoff Jefferson]

Why don't I get output to textField from my actionListener?

The file with interface and listener

 
package gettext;

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class GetText extends JPanel {

    
  public JButton buttonOne = new JButton();

  public JTextField textFieldOne = new JTextField(25);
      
  GetText(){
    super(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
    c.weightx = 0.5;
    JLabel label_1 = new JLabel("Label One");  
          c.gridx = 0;
          c.gridy = 0;
          c.insets = new Insets(5,5,5,5);
          c.anchor = GridBagConstraints.WEST;
        add(label_1, c);
         c.gridx = 0;
         c.gridy = 1;
        add(textFieldOne, c);
         buttonOne = new JButton(" Add To List ");
         c.gridx = 0;
         c.gridy = 2;
         c.gridwidth = 3;
        add(buttonOne,c);
       
  buttonOne.addActionListener(    
    new ActionListener() {
       public void actionPerformed( ActionEvent e)  {
            //Item item = new Item(textFieldOne.getText());
            //textFieldOne.setText("               " + item.myItemString);
            
            SetTextHere setTextHere = new SetTextHere();
            setTextHere.outPut();
           
       }  
        });  
   }
    public static void createAndShowGUI() {

       JFrame frame = new JFrame("Table Model Experiment");
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

       GetText newContentPane = new GetText();
       frame.setContentPane(newContentPane);
        
       frame.setSize(800,500);//(450, 260);
       frame.setVisible(true);
    }  
    public static void main(String[] args) {
       createAndShowGUI();        
    }
}

The File with method in question, called from interface actionListener.

  

package gettext;

public class SetTextHere {
   SetTextHere(){}
    
   public void outPut(){
     GetText getText = new GetText();
     getText.textFieldOne.setText("from setTextHere"); 
   }    

}

[Rob Spoor]

Your SetText object creates a new GetText object, with its own new text field. You probably want to give it a reference to the existing GetText object in the constructor.

[Brian Legg]

I think it has to do with the fact that you are creating 2 GetText objects. Walk through the code.... you are creating the first one in the createAndShowGUI method which is then added to the ContentPane and then set to visible.... but what about the call to SetTextHere.outPut() method? It is also creating a new GetText object. Maybe something different should go here?

[Brian Legg]

Sniped by Rob... again

[Geoff Jefferson]

Your SetText object creates a new GetText object, with its own new text field. You probably want to give it a reference to the existing GetText object in the constructor.

By existing object, are you talking about the one named newContentPane?

[Rob Spoor]

Yes. You can reference it inside your action listener using "GetText.this" - you need the "GetText" prefix because "this" refers to your action listener.

[Geoff Jefferson]

Yes. You can reference it inside your action listener using "GetText.this" - you need the "GetText" prefix because "this" refers to your action listener.

I understand what you are saying. But, the purpose of this exercise is to refer to the textField from another class. I am
having issues with 'fully qualified names', 'qualified names' ect. I'm reading up on the "Java Tutorial" at the moment.

After reading, If I still don't understand I'll post another reply to this thread.

[Geoff Jefferson]

Ok. According to the tutorial,

"You can use a package member's simple name if the code you are writing is in the same package as that member or if that member has been imported."

So, shouldn't I be able to reference the textField like this?

 
package gettext;

public class SetTextHere {
   SetTextHere(){
      textFieldOne.setText("hello");
   }

}

... where the textField being referred to is in the following file.

 
package gettext;

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class GetText extends JPanel {

    
  public JButton buttonOne = new JButton();

  public JTextField textFieldOne = new JTextField(25);
      
  GetText(){
    super(new GridBagLayout());
    GridBagConstraints c = new GridBagConstraints();
    c.weightx = 0.5;
    JLabel label_1 = new JLabel("Label One");  
          c.gridx = 0;
          c.gridy = 0;
          c.insets = new Insets(5,5,5,5);
          c.anchor = GridBagConstraints.WEST;
        add(label_1, c);
         c.gridx = 0;
         c.gridy = 1;
        add(textFieldOne, c);
         buttonOne = new JButton(" Add To List ");
         c.gridx = 0;
         c.gridy = 2;
         c.gridwidth = 3;
        add(buttonOne,c);
       
  buttonOne.addActionListener(    
    new ActionListener() {
       public void actionPerformed( ActionEvent e)  {
            //Item item = new Item(textFieldOne.getText());
            //textFieldOne.setText("               " + item.myItemString);
            
           
           
       }  
        });  
   }
    public static void createAndShowGUI() {

       JFrame frame = new JFrame("Table Model Experiment");
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

       GetText newContentPane = new GetText();
       frame.setContentPane(newContentPane);
        
       frame.setSize(800,500);//(450, 260);
       frame.setVisible(true);
    }  
    public static void main(String[] args) {
       createAndShowGUI();        
    }
}

[Campbell Ritchie]

Bad design, having public fields.
You cannot simply call the name of a field outside its class; the field belongs to an object, so you would have to use the name of the object-dot-name of the field.

[Geoff Jefferson]

which object?

[Campbell Ritchie]

You will have to find an object to pass from the GetText class to the SetText here class. If you are going to do it that way, why not pass a reference to the text field directly?

[Geoff Jefferson]

You will have to find an object to pass from the GetText class to the SetText here class.

This seems to be the big issue here for me. If I understand this correctly, the object that contains the member "textFieldOne"
is "newContentPane". I can't pass it as an argument because it is local to createAndShowGUI.

If you are going to do it that way, why not pass a reference to the text field directly?

Do you mean something like:

  SetTextHere setText = new SetTextHere(textFieldOne);

[Brian Legg]

Yes, you can change your outPut method to accept a JTextField and then pass it in like you just said... Or

You can make your JTextField private, create a getter method for it, and then pass outPut method a reference to your GetText object which then could access the JTextField as needed.

Rob knows more GUI stuff then me but I think the second method is the "correct" way to handle this.

edit: grammar

[Brian Legg]

Actually now that I looked at your code example again... instead of this:

SetTextHere setTextHere = new SetTextHere(textFieldOne);

You don't need to pass the JTextField into your constructor unless you want SetText to keep a permanent reference to it. I would change it to this:

SetTextHere setTextHere = new SetTextHere();
setTextHere.outPut(textFieldOne);

Your design and how these objects will interact will determine which method makes more sense.

[Campbell Ritchie]

Geoff Jefferson wrote:. . . Do you mean something like:

  SetTextHere setText = new SetTextHere(textFieldOne);

Yes, but other people have refined the answer