asked on

SpringLayout problem

Why doesn't the button appear?

package springlayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SpringLayout;

public class SpringLayoutTest extends JPanel{

	public SpringLayoutTest() {
		
		SpringLayout mySpringLayout = new SpringLayout();
		JPanel myPanel = new JPanel(mySpringLayout);

		JButton helloButton = new JButton("hello");
		myPanel.add(helloButton);

		mySpringLayout.putConstraint(SpringLayout.WEST, helloButton, 10, SpringLayout.WEST, myPanel);
		mySpringLayout.putConstraint(SpringLayout.NORTH, helloButton, 10, SpringLayout.NORTH, myPanel);

		this.add(myPanel);
	}

	/**
	 * 
	 * @param s
	 */
	public static void main(String s[]) {

		JFrame frame = new JFrame("SpringLayoutTest");

		SpringLayoutTest springLayoutTest = new SpringLayoutTest();

		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setContentPane(springLayoutTest);
		frame.setSize(300, 300);
		frame.setLocation(300,300);
		frame.setVisible(true);
	}
	
}

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CEHJ

You didn't set the layout on the Container. Try the following

    public SpringLayoutTest() {
        SpringLayout mySpringLayout = new SpringLayout();
	setLayout(mySpringLayout);

        JButton helloButton = new JButton("hello");
        add(helloButton);

        mySpringLayout.putConstraint(SpringLayout.WEST, helloButton, 10,
            SpringLayout.WEST, this);
        mySpringLayout.putConstraint(SpringLayout.NORTH, helloButton, 10,
            SpringLayout.NORTH, this);

    }

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allelopath

ASKER

That's not what I'm looking to do. I want a JPanel that contains a JPanel that is using SpringLayout.

CEHJ

OK. Just use your code, but do

myPanel.setLayout(mySpringLayout);

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allelopath

ASKER

Does this accomplish that?

JPanel myPanel = new JPanel(mySpringLayout);

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CEHJ

Yes, that'll do it

allelopath

ASKER

I already have that, in the original code

ASKER CERTIFIED SOLUTION

CEHJ

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allelopath

ASKER

That works, but I don't understand why. JPanel has FlowLayout as a default layout manager. Why do I have to explicitly set a layout manager?

CEHJ

It's a question of how the subpanel behaves as far as sizing is concerned

SOLUTION

Mick Barry

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