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Pavel

Fri Mar 05, 2010 6:35 pm


In regards to JToolBars

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Hey, I'm trying to understand something about the tutorial given by the Sun Java website. In their code, they set the JToolBar object as a parameter pass in addButtons (), why?
Code below:

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


public class TextTest extends JPanel implements ActionListener
{
    protected JTextArea textArea;
    protected String newline = "\n";
    static final private String PREVIOUS = "previous";
    static final private String DOWN = "down";
    static final private String NEXT = "next";

    public TextTest ()
    {
	super (new BorderLayout ());

	//Create the toolbar.
	JToolBar toolBar = new JToolBar ("Still draggable");
	addButtons (toolBar);

	//Create the text area used for output.  Request
	//enough space for 5 rows and 30 columns.
	textArea = new JTextArea (5, 30);
	textArea.setEditable (false);
	JScrollPane scrollPane = new JScrollPane (textArea);

	//Lay out the main panel.
	setPreferredSize (new Dimension (450, 130));
	add (toolBar, BorderLayout.PAGE_START);
	add (scrollPane, BorderLayout.CENTER);
    }


    protected void addButtons (JToolBar toolBar)
    {
	JButton button = null;

	//first button
	button = makeNavigationButton ("Back24", PREVIOUS, "Back to previous something-or-other", "Previous");
	toolBar.add (button);

	//second button
	button = makeNavigationButton ("Down24", DOWN, "Down to something-or-other", "Up");
	toolBar.add (button);

	//third button
	button = makeNavigationButton ("Forward24", NEXT, "Forward to something-or-other", "Next");
	toolBar.add (button);
    }


    protected JButton makeNavigationButton (String imageName, String actionCommand, String toolTipText, String altText)
    {
	String imgLocation = imageName + ".gif";
	Image imageGIF = Toolkit.getDefaultToolkit ().getImage (imgLocation);

	//Create and initialize the button.
	JButton button = new JButton ();
	button.setActionCommand (actionCommand);
	button.setToolTipText (toolTipText);
	button.addActionListener (this);

	button.setIcon (new ImageIcon (imageGIF, altText));

	return button;
    }



    protected void displayResult (String actionDescription)
    {
	textArea.append (actionDescription + newline);
	textArea.setCaretPosition (textArea.getDocument ().getLength ());
    }


    public void actionPerformed (ActionEvent e)
    {
	String cmd = e.getActionCommand ();
	String description = null;

	// Handle each button.
	if (PREVIOUS.equals (cmd))
	{ //first button clicked
	    description = "taken you to the previous .";
	}
	else if (DOWN.equals (cmd))
	{ // second button clicked
	    description = "taken you down one level to .";
	}
	else
	{
	    if (NEXT.equals (cmd))
	    { // third button clicked
		description = "taken you to the next .";
	    }
	}

	displayResult ("If this were a real app, it would have " + description);
    }
}




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Barbarrosa

Fri Mar 05, 2010 9:51 pm


Re: In regards to JToolBars

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They are using "addButtons" to divide the code into smaller chunks. It takes the JToolbar, then adds buttons to it.

The method needs to have a reference to the JToolbar so it can add buttons.


protected void addButtons (JToolBar toolBar)
{
JButton button = null;

//first button
button = makeNavigationButton ("Back24", PREVIOUS, "Back to previous something-or-other", "Previous");
toolBar.add (button);

//second button
button = makeNavigationButton ("Down24", DOWN, "Down to something-or-other", "Up");
toolBar.add (button);

//third button
button = makeNavigationButton ("Forward24", NEXT, "Forward to something-or-other", "Next");
toolBar.add (button);
}