Setting size of JButton

[Shubham Semwal]

How to set size of Jbutton. It's taking all the space in the frame.

public class JButtonDemo {
	JFrame frame;
	JButton button;
	
	public static void main(String[] args) {
		
		JButtonDemo jbd = new JButtonDemo();
				jbd.frame = new JFrame("FirstFrame");
				jbd.frame.setVisible(true);	
				jbd.frame.setSize(300, 300);
				jbd.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
				jbd.button = new JButton("Click Me !!");
				jbd.button.setBounds(100, 100, 100, 80);
				
				jbd.frame.add(jbd.button);
	}
	
}

[Ahmed Bin S]

I haven't used Swing since I created a document editor at university for a project over 15 years ago, but as far as I remember, you add buttons to a JPanel and not directly to the JFrame. So you're looking at something like the below, but it might not be the best way to do it.

JPanel panel = new JPanel();
panel.add(jbd.button);
jbd.frame.setContentPane(panel);

[Paul Clapham]

You'll want to learn about LayoutManagers to solve that problem. You've "decided" to use the default LayoutManager, which I forget what that is but anyway it makes components take up as much space as possible.

Here's the tutorial: A Visual Guide to Layout Managers.

[Shubham Semwal]

Thanks Paul. Looking at it

[Maneesh Godbole]

1) The recommended way is to use setPreferredSize() and not setBounds()
2) You need to use a layout for the parent which will honour the preferred size.

So effectively
Create a JPanel instance
It defaults to FlowLayout which DOES honour the preferred size
Set the preferred size to the button
Add the button to the panel

[Fred Kleinschmidt]

Why do you want to set the size of the button? Why not let it be the size it naturally prefers, based on the text it contains? Setting its exact size is rarely a good idea and might make your code non-portable since some other platform might have a different default font, or might have a different screen resolution. and it means that if you ever decide to use a different font than the default, or use a different text, you will have to re-measure everything and modify all of your sizes so the text fits. You should be using a layout manager that does all this for you.

[Shubham Semwal]

Not getting most of the replies
But I'm able to get it to center using BorderLayout.
@Maneesh - I was not using Jpanel anywhere. I'll take a look for its functionality.

Fred Kleinschmidt wrote:You should be using a layout manager that does all this for you.

@Fred - Which layout manager does this automatically ?

[Shubham Semwal]

I tried but not getting how to use JPanel.

public class JPanelDemo {

	private JFrame frame;
	private JPanel panel;
	
	private void setFrame() {
		frame = new JFrame("MyFrame");
		frame.setSize(300, 300);
		frame.setLayout(null);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setBounds(500, 200, 300, 300);
		
		setPanel();
	}
	
	private void setPanel() {
		panel = new JPanel(new BorderLayout());
			panel.setBackground(Color.BLACK);
			panel.setBorder(new CompoundBorder());
		
		
		
		panel.add(new JButton("Click me"), BorderLayout.CENTER);
		frame.add(panel);
				
	}
	
	private void doStuff(){
		setFrame();
		panel.setVisible(true);
		frame.setVisible(true);
	}
	
	public static void main(String[] args) {
		JPanelDemo jpd = new JPanelDemo();
			jpd.doStuff();
					
	}
}

[Campbell Ritchie]

No layout manager does everything automatically; you must give it the details of the sizes you require. Don't make the frame and the panel fields; make them local variables. Don't use several methods to set up the GUI. This is the one occasion where you are allowed a very long method (or very long constructor). Don't set your layout to null. Don't use setSize and setBounds; use setBounds only for the top‑level container (=the frame). Don't call setVisible twice; call it once on the frame, but it shoiuld be the last statement.

[Maneesh Godbole]

Shubham Semwal wrote:I tried but not getting how to use JPanel.

Note the code comments

package com.coderanch.test;

import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class Test {

	public static void main(String[] args) {
		SwingUtilities.invokeLater(new Runnable() {
			
			@Override
			public void run() {
				JFrame frame = new JFrame();
				frame.setSize(800,600);
				frame.setLocationRelativeTo(null);
				frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				
				JButton button = new JButton("Click me");
				//Explicitly set the size to what you want
				button.setPreferredSize(new Dimension(100, 100));
				
				//Content pane default layout is BorderLayout which does NOT
				//Respect the preferred sizes. Set it to FlowLayout which does
				frame.getContentPane().setLayout(new FlowLayout());
				frame.getContentPane().add(button);
				
				//Finally display the frame
				frame.setVisible(true);
			}
		});
	}
}

[Shubham Semwal]

Thanks Maneesh. I'm able to see panel now.