GUI and events

[Dianne Gerrelli]

I am having trouble with a programme that I am writting which is designed to desplay a GUI and then perform tasks depending on the user selecting buttons displayed in the GUI. I have managed to get everything to display but the problem I have is that I can not catch the events ie nothing happens when I select any of the buttons.

The programme is divided into seperate classes so I think this could be due to a problem with the classes not communicating as i am not really sure if the variables that I have are in the correct place. They are supposed to act as handles enabling one class to access information in another.

The alternative is that I have a problem with the way I have setup the actionListeners. I have tried to put a very simple test to see if any buttons are pressed and if so then print a message out to the Crimson Editor screen rather than the GUI but this does not work.

If anyone has any advice on how I can test this further or can spot my errors I would be most grateful.

The classes I have at present are

1. QuitableJFrame is a file I have been supplied with and handles the closing of the GUI

2. TranslationTool sets up the GUI frame

3. Translator class handles the events from the buttons and then "does task". This class does most of the real work

Then there are 3 Panel classes:-

4. TranslationPanel sets up JTextArea's for input output of text

5. InformationPanel sets up Jtext fields and Jlabel fields. One of which is the status of the programme

6. ControlPanel class sets up buttons for the user of the GUI to select

Full code is shown below.

Best wishes
Dianne

 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**
 * A Frame which provides default implementations for the
 * WindowListener events. These do nothing, except for
 * WindowClosing, which pops up a dialog box to check if
 * we want to quit, and if so destroys the Frame and exits
 * the program.
 */
public class QuitableJFrame extends JFrame implements WindowListener {
 
/**
 * Construct a quitable JFrame with the given title and size.
 */
public QuitableJFrame ( String title, int xpixels, int ypixels ) {
super(title);
this.addWindowListener(this);
      if (xpixels > 0 && ypixels > 0) this.setSize(xpixels, ypixels);
      this.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
}
 
public QuitableJFrame( String title ) {
this(title, 0, 0);
}
 
/**
 * Utility method to pop up an InputDialog when we want
 * a value from the user
 */
public int getValueFromUser(String msg, int defaultValue) {
String valueString = JOptionPane.showInputDialog(this, msg, 
"input value", JOptionPane.QUESTION_MESSAGE);
if (valueString == null) return defaultValue;
else
try {
int value = Integer.parseInt(valueString);
return value;
}
catch (NumberFormatException e) {
return defaultValue;
}
} // getValueFromUser
/** Test program */
public static void main(String[] args) {
JFrame f = new QuitableJFrame("Test", 300, 300);
// We'll handle closing, so...
f.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
f.show();
}
/** Utility to pop up a quit/cancel dialog associated with the
* frame.
*/
public void quitOrCancel() {
int result = JOptionPane.showConfirmDialog(this,
"Quit " + this.getTitle() + "?",
"Just making sure...",
JOptionPane.YES_NO_OPTION);
if (result == JOptionPane.YES_OPTION) System.exit(1);
}
/** utility to pop up a message dialog
*/
public void tellUser(String msg) {
JOptionPane.showMessageDialog(this, msg, "Information",
JOptionPane.INFORMATION_MESSAGE);
}
/** Utility to pop up a warning message dialog
*/
public void warnUser(String warning) {
JOptionPane.showMessageDialog(this, warning, "Warning",
JOptionPane.WARNING_MESSAGE);
}
/** Default implementation does nothing */
public void windowActivated(WindowEvent e){}
/**
 * Default implementation does nothing
 */
public void windowClosed( WindowEvent e) { }
/**
 * Default implementation pops up a dialog box, which if accepted
 * destroys the frame and quits the whole application 
 * with System.exit.
 */
public void windowClosing(WindowEvent e)  {
this.quitOrCancel();
}
/** Default implementation does nothing */
public void windowDeactivated(WindowEvent e){}
/**
 * Default implementation does nothing.
 */
public void windowDeiconified( WindowEvent e) { }
/**
 * Default implementation does nothing.
 */
public void windowIconified( WindowEvent e) {
}
/**
 * Default implementation does nothing.
 */
public void windowOpened( WindowEvent e) {
}
 
  /** Set the look and feel. The argument is the full name of the
  * desired look&feel class, e.g.
  * com.sun.java.swing.plaf.windows.WindowsLookAndFeel
  */
  public void setLookAndFeel(String lookAndFeel) {
try { 
  // Set the look and feel for the system..
  UIManager.setLookAndFeel(lookAndFeel);
  // .. and tell all the components about it.
  SwingUtilities.updateComponentTreeUI(this);
  // Call the layout manager in case things need shuffling around.
  this.validate();
  // And display the result of all that.
  this.repaint();
  // Indicate success
  // System.out.println("Look and feel set to " + lookAndFeel );
}
catch(Exception e) {
  // Indicate if desired L&F wasn't available for some reason.
  System.out.println(e);
}
  }         
 
}
   

  import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
/** TranslationTool sets up the GUI frame and adds panels and panes to this frame*/
/**Also sets up the menu bar for opening files*/
/** Sets up a new GUI in main using a new TranslationTool object*/
/**A private instance variable of type Translator has been setup and this is 
passed to the constructor of the ControlPanel so that the buttons can be registered*/
 
public class TranslationTool extends QuitableJFrame {

private Translator translate ;
 

public TranslationTool(){

super ("TranslationTool");

  this.getContentPane().setLayout(new BorderLayout());
  
  InformationPanel information = new InformationPanel();
  this.getContentPane().add(information, BorderLayout.NORTH);
  
TranslationPanel translation = new TranslationPanel();
this.getContentPane().add(translation, BorderLayout.CENTER);

ControlPanel control = new ControlPanel(translate);
 this.getContentPane().add(control, BorderLayout.SOUTH);
 
  this.pack();
  this.show();}
  
/**private void setupMenubar() {
 
 JMenuBar theBar = new JMenuBar();
 JMenu fileMenu = new JMenu ("File");
 JMenuItem quitItem = new JMenuItem ("Quit");
 quitItem.addActionListener (this);
 fileMenu.add(quitItem);
 theBar.add(fileMenu);
 this.setJMenuBar(theBar);}
 JMenuItem open = new JMenuItem ("Open");
 JMenuItem save = new JMenuItem ("Save");
 JMenuItem saveAs = new JMenuItem ("SaveAs");
 fileMenu.add (open);
 fileMenu.add (save);
 fileMenu.add (saveAs);}
 open.addActionListener (this);
 save.addActionListener (this);
 saveAs.addActionListener (this);*/
 
 
 
 
   public static void main(String[] args) {
 
/**Creates the new GUI*/
 TranslationTool  tool = new TranslationTool ();
}
 

    
}
  

   import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.event.*;
 
/** The Translator class will handle the events from the buttons and do the real work*/
/**This is the only class at present which is defined to implement ActionListener
so all events need to be caught in this class*/
 
public class Translator   implements ActionListener{
 

/** Private instance variables setup so that the Translator class can access a reference 
to the various different classes, ie parent.getinformationPanel()*/

private TranslationTool parent ;
private InformationPanel information;
private ControlPanel control;

/** Private instances of each class past into the constructor of the Translator class 
as parameters*/


public Translator(TranslationTool parent, InformationPanel information, ControlPanel control){

  this.parent = parent; 
  this.information = information;
  this.control = control;
}

/**File chooser used to select the file for opening*/ 
JFileChooser fc = new JFileChooser();


/** Method to get any action performed on the GUI and then do something
ie if revcomp button pressed get sequence content and description for file and 
pass them to a new sequence object. the revcomp method is then called by the 
sequence object and the verversed and complementary sequence is returned to the output
JTextArea in the GUI.*/


public void actionPerformed (ActionEvent event){


String action = event.getActionCommand();

if (action.equals ("revcomp"))

/**Test to see if the events are being caught, but this does not work*/
System.out.println ("An action has occurred " );

else {System.out.println ("nothing " );}
}

} 

   import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**import java.lang.Object.*;*/
 
/**TranslationPanel sets up JTextArea's for input output of text*/
 

public class TranslationPanel extends JPanel {

private JTextArea inputArea;  
private JTextArea ouputArea;

public TranslationPanel(){


JTextArea inputArea = new JTextArea("Input area", 20, 20);
this.add (inputArea);
 
JTextArea outputArea = new JTextArea("Output area", 20, 20);
 this.add (outputArea);
 
/**String text = textArea.gettext();
inputArea.setText("this text");*/
 

}
} 

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

/**InformationPanel sets up 2 Jtext fields and Jlabel fields*/
/**They are named Description and Status*/
/**Description is the name of the file that is being used*/
/**Status is designed to display the name of the button 
pressed so that the user knows the somethig is happening*/
 
public class InformationPanel extends JPanel  {

private JTextField description, status;
 

public InformationPanel(){

 this.setLayout(new GridLayout(2,2));
 
  this.add(new JLabel("Description"));
  this.add(new JLabel("Status"));
  
  
  this.add(description = new JTextField());
  this.add(status = new JTextField());
  
  
 status.setEditable(false);
} 
 
} 

 import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
/**ControlPanel class sets up buttons for the user of the GUI to select*/
/**It is passed an instance of the Translator class so that this can be 
used to register the buttons. The instance variable passed in as a 
parameter is copied into a local variable*/
 

public class ControlPanel extends JPanel  {

public ControlPanel(Translator translate){

Translator translating = translate; 

  JButton revCompButton, simpleButton, frameButton, getORFButton, clearButton;
 
 
  this.add(revCompButton = new JButton("revcomp"));
  revCompButton.addActionListener(translating);
  
 this.add(simpleButton = new JButton("simple"));
  simpleButton.addActionListener(translating);
  
  this.add(frameButton = new JButton("6 frame"));
  frameButton.addActionListener(translating);
  
  this.add(getORFButton= new JButton("get ORF"));
  getORFButton.addActionListener(translating);
  
  this.add(clearButton = new JButton("clear"));
  clearButton.addActionListener(translating);
  
} 
 
}   

[marc weber]

It appears that your entry point is TranslationTool. Take a look at the main method there and walk through the constructor calls to make sure that everything is getting created the way you intend.

I think one thing you will find is that no instance of Translator (where everything is supposed to get "connected") is ever created.

Also, the way it's written now, the Translator constructor needs a reference to the ControlPanel, but the ControlPanel constructor needs a reference to the Translator. (The ControlPanel constructor is currently getting a null reference.)

For some guidance on how to connect everything, you might want to do some searching on the Model View Controller (MVC) pattern.
[ February 08, 2006: Message edited by: marc weber ]

[Dianne Gerrelli]

Thanks I will take a look at Model View Controller

Best wishes
Dianne

[Dianne Gerrelli]

I have spent sometime reading about implementing the Model View Controller and have attempted to hook my classes up in a similar fashion.

The TranslationTool is designed as the parent class and as such needs access to all the classes. I have therefore given it instance variables to all the classes and set them within the constructor of the TranslationTool using

    this.translator = translator;
this.information = information;
 this.control = control;
 this.translation = translation;

The Translator class which listens for the events and does most of the work is passed an instance of the TranslationTool as a parameter of its constructor. This is then copied into a variable inside the constructor.

    
public Translator(TranslationTool parent){

  this.parent = parent;
}

I think that this class will be able to access all other classes if it uses �parent�



The ControlPanel class public is passed an instance of the Translator class as a parameter of its constructor. This is then copied into a variable inside the constructor.

    
ControlPanel(Translator theTranslator){

Translator translating = theTranslator;
}

Can anyone please explain the difference of using � this.� And just simple copying it into a local variable within the constructor???


The TranslationPanel and InformationPanel do not have any link except via the TranslationTool, since it has an instance variable to each class.

I have some get methods which are designed to get at each panel and the use the result to get at the text within the panel.

My main problem is that everything looks beautiful but nothing is functioning. I have setup tests to catch when buttons are pressed and are supposed to print out if a button is hit but nothing is happening.

I would be very grateful for any advice particularly on how to check if events are happening or if there are glaring mistakes in my logic.

I will paste the full code below.

Best wishes
Dianne

TranslationTool sets up the GUI frame

Translator class handles the events from the buttons and then "does task". This class does most of the real work

3 Panel classes:-

TranslationPanel
InformationPanel
ControlPanel

QuitableJFrame is a file I have been supplied with and handles the closing of the GUI

  
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;
 
/** TranslationTool sets up the GUI frame and adds panels and panes to this frame*/
/**Also sets up the menu bar for opening files*/
/** Sets up a new GUI in main using a new TranslationTool object*/
/**A private instance variable of type Translator has been setup and this is 
passed to the constructor of the ControlPanel so that the buttons can be registered*/
 
public class TranslationTool extends QuitableJFrame implements ActionListener{


/**Instance variables to be used as handles to obtain information in other classes*/
private Translator translator;
private InformationPanel information;
private ControlPanel control;
private TranslationPanel translation;
 

 
/**Constructor of class*/
/**The super constructor is used to setup the title bar*/
 
public TranslationTool(){

super ("TranslationTool");


/**Setting up instance variables within the constructor to be used as handles*/
  this.translator = translator;
  this.information = information;
  this.control = control;
  this.translation = translation;

/**Set the overall layout*/
  this.getContentPane().setLayout(new BorderLayout());
  
  
 /**Creates new Panel objects and adds them to the ContentPane*/
  
  InformationPanel information = new InformationPanel();
 this.getContentPane().add(information, BorderLayout.NORTH);
  
TranslationPanel translation = new TranslationPanel();
this.getContentPane().add(translation, BorderLayout.CENTER);

ControlPanel control = new ControlPanel(translator);
 this.getContentPane().add(control, BorderLayout.SOUTH);
 
/**Calls the utility method to setup the menu bar*/
 this.setUpMenuBar();
 
/** Creates a new Translator object*/
 Translator theTranslator = new Translator (this);
 
/**Creates a new ControlPanel object*/
 ControlPanel theControlPanel = new ControlPanel (theTranslator); 
 
  this.pack();
  
  this.show();
  
  }
/**End of constructor*/  
 
  
  
/**Utility method to create a new menu bar*/
private void setUpMenuBar() {
 
 JMenuBar menuBar = new JMenuBar();
 
 JMenu menu = new JMenu ("A menu");
 
 JMenuItem quitItem = new JMenuItem ("Quit");
 JMenuItem open = new JMenuItem ("Open");
 JMenuItem save = new JMenuItem ("Save");
 JMenuItem saveAs = new JMenuItem ("SaveAs");
 
 menuBar.add(menu);
 
 menu.add(quitItem);
 menu.add(open);
 menu.add(save);
 menu.add(saveAs);
 
 quitItem.addActionListener (this); 
 open.addActionListener (this);
 save.addActionListener (this);
 saveAs.addActionListener (this);
 
this.setJMenuBar (menuBar);

 }
 
 
 
 /** Implement the actionPerformed method but do nothing as all events 
 will be caught in the Translator class*/
 
public void actionPerformed (ActionEvent e){
 
 }
 
 
public static void main(String[] args) {
 
/**Creates the GUI*/
 TranslationTool  tool = new TranslationTool ();
 
}
  
}

/** End of TranslationTool class*/  

  
 
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;
 

/** The Translator class will handle the events from the buttons and do the real work*/
/**This class implements the ActionListener, all events need to be caught in this class*/
 
public class Translator   implements ActionListener{
 

/** Private instance variables setup so that the Translator class can access a reference 
to TranlationTool different classes*/

private TranslationTool parent ;
private TranslationPanel translation;
private ControlPanel control;
private InformationPanel information;


/**Constructor of class*/
/** Private instances of TranslationTool past as a parameter of the constructor 
Instances which will refer to the 3 panels classes are set inside the constructor.
*/
 
public Translator(TranslationTool parent){

  this.parent = parent; 
  this.translation = translation;
  this.control = control;
  this.information = information;
  
}

/** End of constructor*/
 

 
/**File chooser used to select the file for opening*/ 
JFileChooser fc = new JFileChooser();



/** Lisener for all events here*/
/**This does not work at present but I am not sure why*/

public void actionPerformed (ActionEvent event){


/** The lines below do not compile 
I am trying to get at user input for the description and content
these will then be used to produce a Sequence object. 
Once the Sequence object is created setup a test to see what the user wants to do.
Test for equality which button was presses by the user
Do what ever action necessary by calling external methods and 
 return the altered sequence to the output field*/
 

/**InformationPanel iPanel = parent.getInformationPanel();
String description = iPanel.getDescriptionText();

TranslationPanel tPanel = parent.getTranslationPanel();
String content = tPanel.getinputAreaText();*/


String action = event.getActionCommand();

if (action.equals ("revcomp"))System.out.println ("rev" );

else if (action.equals ("simple"))System.out.println ("simple" );
else if (action.equals ("6 frame"))System.out.println ("6 frame" );
else if (action.equals ("get ORF"))System.out.println ("get ORF" );
else if (action.equals ("clear"))System.out.println ("clear" );

}

}
 
/** End of Translator class*/
  

  
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.Object.*;
 

 
/**TranslationPanel sets up JTextArea's for input output of text*/
 

public class TranslationPanel extends JPanel {

/**Instance variables to be used as handles to obtain information in other classes*/
private JTextArea inputArea, ouputArea;  
private TranslationPanel tPanel;


/**Constructor of class*/
/**Set up 2 JTextArea's for input and output of text*/
 
public TranslationPanel(){

JTextArea inputArea = new JTextArea(20, 20);
this.add (inputArea);
 
JTextArea outputArea = new JTextArea( 20, 20);
 this.add (outputArea);
 
}
/** End of constructor*/


 

/**Methods to be used to pass information to other classes*/
 
public TranslationPanel getTranslationPanel (TranslationPanel tPanel){

return tPanel;
}
 


 public String getinputAreaText() {
 
String input = null; 

 return input  = (inputArea.getText());
}
}
 
/** End of TranslationPanel class*/  

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

/**InformationPanel sets up 2 Jtext fields and Jlabel fields*/
/**They are named Description and Status*/
/**Description is used to enter the description of the sequence object*/
/**Status is designed to display the name of the button 
pressed so that the user knows the somethig is happening*/
 
public class InformationPanel extends JPanel  {

/**Instance variables to be used as handles to obtain information in other classes*/
private JTextField description, status;
private InformationPanel iPanel;
 


/**Constructor of class*/
/**Sets the labels side by side with the respective TextFields below*/
/**Status should not be changed by the user, so is defined as not editable*/
 
public InformationPanel(){
 
 this.setLayout(new GridLayout(2,2));
 
  this.add(new JLabel("Description"));
  this.add(new JLabel("Status"));
  
  this.add(description = new JTextField());
  this.add(status = new JTextField());
 
  status.setEditable(false);
}
/** End of constructor*/
 

 
/**Methods to be used to pass information to other classes*/
 
public InformationPanel getInformationPanel (InformationPanel iPanel){

return iPanel;
}
 


 public String getDescriptionText() {
 
String textDescription = null; 

 return textDescription  = (description.getText());

 }
 
}

/** End of InformationPanel class*/  

   import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
/**ControlPanel class sets up buttons for the user of the GUI to select*/
/**It is passed an instance of the Translator class so that this can be 
used to register the buttons. The instance variable passed in as a 
parameter is copied into a local variable*/
 

public class ControlPanel extends JPanel  {
 
/**Instance variables to be used as handles to obtain information in other classes*/
private JButton revCompButton, simpleButton, frameButton, ORFButton, clearButton;
private ControlPanel cPanel;




/**Constructor of class*/
/** An instance of the Translator class is past in as a parameter 
so it can be used to register each button*/
 
public ControlPanel(Translator theTranslator){

/** Copying the instance of Translator into a local variable within the constructor*/
Translator translating = theTranslator; 

/**Local variables */
JButton revCompButton, simpleButton, frameButton, getORFButton, clearButton;


/**Add the new buttons to the ControlPanel and attach an ActionListener to each*/ 
  this.add(revCompButton = new JButton("revcomp"));
  revCompButton.addActionListener(translating);
  
 this.add(simpleButton = new JButton("simple"));
  simpleButton.addActionListener(translating);
  
  this.add(frameButton = new JButton("6 frame"));
  frameButton.addActionListener(translating);
  
  this.add(getORFButton= new JButton("get ORF"));
  getORFButton.addActionListener(translating);
  
  this.add(clearButton = new JButton("clear"));
  clearButton.addActionListener(translating);
  
} 
/** End of constructor*/

 

/**Methods to be used to pass information to other classes*/
 
public ControlPanel getControlPanel (ControlPanel cPanel){

return cPanel;

}
 
}

/** End of ControlPanel class*/ 

  
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**
 * A Frame which provides default implementations for the
 * WindowListener events. These do nothing, except for
 * WindowClosing, which pops up a dialog box to check if
 * we want to quit, and if so destroys the Frame and exits
 * the program.
 */
public class QuitableJFrame extends JFrame implements WindowListener {
 
/**
 * Construct a quitable JFrame with the given title and size.
 */
public QuitableJFrame ( String title, int xpixels, int ypixels ) {
super(title);
this.addWindowListener(this);
      if (xpixels > 0 && ypixels > 0) this.setSize(xpixels, ypixels);
      this.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
}
 
public QuitableJFrame( String title ) {
this(title, 0, 0);
}
 
/**
 * Utility method to pop up an InputDialog when we want
 * a value from the user
 */
public int getValueFromUser(String msg, int defaultValue) {
String valueString = JOptionPane.showInputDialog(this, msg, 
"input value", JOptionPane.QUESTION_MESSAGE);
if (valueString == null) return defaultValue;
else
try {
int value = Integer.parseInt(valueString);
return value;
}
catch (NumberFormatException e) {
return defaultValue;
}
} // getValueFromUser
/** Test program */
public static void main(String[] args) {
JFrame f = new QuitableJFrame("Test", 300, 300);
// We'll handle closing, so...
f.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
f.show();
}
/** Utility to pop up a quit/cancel dialog associated with the
* frame.
*/
public void quitOrCancel() {
int result = JOptionPane.showConfirmDialog(this,
"Quit " + this.getTitle() + "?",
"Just making sure...",
JOptionPane.YES_NO_OPTION);
if (result == JOptionPane.YES_OPTION) System.exit(1);
}
/** utility to pop up a message dialog
*/
public void tellUser(String msg) {
JOptionPane.showMessageDialog(this, msg, "Information",
JOptionPane.INFORMATION_MESSAGE);
}
/** Utility to pop up a warning message dialog
*/
public void warnUser(String warning) {
JOptionPane.showMessageDialog(this, warning, "Warning",
JOptionPane.WARNING_MESSAGE);
}
/** Default implementation does nothing */
public void windowActivated(WindowEvent e){}
/**
 * Default implementation does nothing
 */
public void windowClosed( WindowEvent e) { }
/**
 * Default implementation pops up a dialog box, which if accepted
 * destroys the frame and quits the whole application 
 * with System.exit.
 */
public void windowClosing(WindowEvent e)  {
this.quitOrCancel();
}
/** Default implementation does nothing */
public void windowDeactivated(WindowEvent e){}
/**
 * Default implementation does nothing.
 */
public void windowDeiconified( WindowEvent e) { }
/**
 * Default implementation does nothing.
 */
public void windowIconified( WindowEvent e) {
}
/**
 * Default implementation does nothing.
 */
public void windowOpened( WindowEvent e) {
}
 
  /** Set the look and feel. The argument is the full name of the
  * desired look&feel class, e.g.
  * com.sun.java.swing.plaf.windows.WindowsLookAndFeel
  */
  public void setLookAndFeel(String lookAndFeel) {
try { 
  // Set the look and feel for the system..
  UIManager.setLookAndFeel(lookAndFeel);
  // .. and tell all the components about it.
  SwingUtilities.updateComponentTreeUI(this);
  // Call the layout manager in case things need shuffling around.
  this.validate();
  // And display the result of all that.
  this.repaint();
  // Indicate success
  // System.out.println("Look and feel set to " + lookAndFeel );
}
catch(Exception e) {
  // Indicate if desired L&F wasn't available for some reason.
  System.out.println(e);
}
  }         
 
}
  

[Dianne Gerrelli]

I have moved on to a second problem with my programme while I wait for advice on my original post about events. I though it best to keep to this thread but please advise if it is preferable to start a new thread.

I need to set up FileChoosers to allow me to make use of my menu options in my GUI ie Open, Save and SaveAs.

I am a like confused as to the order and where code should be placed. I have tried to put some very basic code to initiate and use a fileChooser within my Translator class but I am begining to thing that it should be in a seperate class. However if I put it in a seperate class I get back to my origninal problem, ie I do not think that the classes are communicating and at present can not figure out any way of testing to determine what is wrong.

I have pasted the code I am tring to use below. It is in the actionPerformed method because I need to catch the event of selecting a menu option.

 /** Lisener for all events here*/
 
public void actionPerformed (ActionEvent event){

int returnVal;
File selectedFile = null;
 

 
 JFileChooser fileChooser = new JFileChooser();
 
String action = event.getActionCommand();


/**Response to a menu item being selected */
 
if (action.equals ("open"))System.out.println ("open" );{

 returnVal = fileChooser.showOpenDialog(this);
 }
 
 
/** Checks for user input */
  if(returnVal == JFileChooser.APPROVE_OPTION){
  
    selectedFile = fileChooser.getSelectedFile();
    
  }   

However I get a compilation error which is

---------- Capture Output ----------
> "C:\Program Files\Java\jdk1.5.0\bin\javac.exe" Translator.java
Translator.java:68: showOpenDialog(java.awt.Component) in javax.swing.JFileChooser cannot be applied to (Translator)
returnVal = fileChooser.showOpenDialog(this);
^
This seems to say that the JFileChooser can not be used within the Translator class.

Can someone please let me know if this is correct and if so suggest how I can capture the initial event of selecting the menu item outside of this class. I think it is again a case of using "parent." but since I can not get this to work properly I am not so sure.

Hope someone can help me understand what I am doing wrong.

Best wishes
Dianne Gerrelli

PS Anyone know why I am a Ranch Hand know instead of a Green Horn ?
It is quite flattering but I am afraid I am definitely still learning but would really like to learn and use Java.

[Ulf Dittmer]

A few things in no particular order:

The following is code to use a JFileChooser. The javadocs for javax.swing.JFileChooser also have an example of how to use it.

JFileChooser = new JFileChooser(System.getProperty("user.dir"));
fd.setDialogTitle("Choose file to load");
if (fd.showOpenDialog(this) != JFileChooser.APPROVE_OPTION)
return false; // this means the user cancelled out of the dialog
String currentDir = fd.getCurrentDirectory().getAbsolutePath();
File inputFile = fd.getSelectedFile();

Going back to what Marc said, make sure (e.g. by System.out.println) that the references you pass around as parameters to the constructors are not null.

Regarding "this": It refers to the current object instance. If you write "this.parent", then you're referring to a instance field called "parent", not to a field called "parent" in the current method. In the following code, the left side of the assignment refers to "Object parent", while the right side refers to "TranslationTool parent":

Object parent;
public Translator (TranslationTool parent) {          
    this.parent = parent;
}

You're now a ranch hand because you posted more than 30 times - it is an automatic promotion, with no checking on your Java progress. Wear it proudly, even if you feel you haven't earned it yet - next time, there will be an exam
[ February 11, 2006: Message edited by: Ulf Dittmer ]

[Dianne Gerrelli]

Thanks for the reply I will see if I can make further progress. I will post later today with either more questions or hopefully the functioning GUI.

Best wishes
Dianne