Thread: Jframe title setting question

tl;dr version: there is no real difference. One calls the constructor, another calls the setTitle() method. They both go up to Frame, which sets its title variable.

Look at the code for JFrame (the source is available):

   public JFrame(String title) throws HeadlessException {
        super(title);
        frameInit();
    }
 
   //there is no setTitle() method in JFrame

And for Frame:

    public Frame(String title) throws HeadlessException {
        init(title, null);
    }
 
    private void init(String title, GraphicsConfiguration gc) {
        this.title = title;
        SunToolkit.checkAndSetPolicy(this, false);
    }
 
    public void setTitle(String title) {
        String oldTitle = this.title;
        if (title == null) {
            title = "";
        }
 
 
        synchronized(this) {
            this.title = title;
            FramePeer peer = (FramePeer)this.peer;
            if (peer != null) {
                peer.setTitle(title);
            }
        }
        firePropertyChange("title", oldTitle, title);
    }

Does that answer your question?

Originally Posted by derekxec

that does thank you very much...the book im reading says you can set either way but doesnt explain why you can or why you should set it this way over that way

Use the constructor if you know the title at time you're creating a JFrame (which will be most cases, which is probably why it's provided. Use setTitle() if you have to set or change the title after the JFrame has already been created.

Originally Posted by william

Kevin, I have a question for you. You used firePropertyChange what is the purpose for this and why. Sorry I have never figured out how to use this properly.

thanks,

Correction- I didn't use anything, that's just code I copied from the JDK source. Presumably, the firePropertyChange() method is called to generate a PropertyChangeEvent, which will be caught by any PropertyChangeListeners listening for the "title" property. For example:

import java.awt.event.*;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
 
import javax.swing.*;
 
 
public class FrameListenersTest {
 
 
	public FrameListenersTest(){
 
		final JFrame frame = new JFrame("Listeners Test");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(200, 200);
 
		frame.addPropertyChangeListener("title", new PropertyChangeListener(){
 
			@Override
			public void propertyChange(PropertyChangeEvent e) {
				System.out.println("Old: " + e.getOldValue());
				System.out.println("New: " + e.getNewValue());
				System.out.println();
			}
 
		});
 
 
 
		frame.setVisible(true);
 
 
		Timer timer = new Timer(2000, new ActionListener(){
			int i = 0;
			public void actionPerformed(ActionEvent e){
				i++;
				frame.setTitle("Title " + i);
			}
		});
 
		timer.start();
	}
 
 
 
	public static void main(String... args){
		new FrameListenersTest();
	}
}

PS- The person who wrote the code that uses the PropertyChangeListener in the Frame class seems to be Sami Shaio. I think he wrote a lot of the stuff in AWT. That's your bit of trivia for the day.