Why JLabel has zero height when using SpringLayout?

Question

I new in Java UI design and I try to use SpringLayout to create form. I put JLabel in JFrame, added some constraints. I need JLabel that stratches to JPanel width. But it has zero height. And too small width.

Here is code fragment:

imageContainer = new JLabel();
imageContainer.setBorder(BorderFactory.createLineBorder(Color.BLACK));

filterButton = new JButton("Filter");
filterButton.addActionListener(filter);

layout.putConstraint(SpringLayout.WEST, imageContainer, 5, SpringLayout.WEST, this);
layout.putConstraint(SpringLayout.NORTH, imageContainer, 5, SpringLayout.NORTH, this);
layout.putConstraint(SpringLayout.EAST, imageContainer, 5, SpringLayout.EAST, this);

layout.putConstraint(SpringLayout.WEST, filterButton, 5, SpringLayout.WEST, this);
layout.putConstraint(SpringLayout.NORTH, filterButton, 5, SpringLayout.SOUTH, imageContainer);
layout.putConstraint(SpringLayout.SOUTH, filterButton, 5, SpringLayout.SOUTH, this);

And this is the result

Where did I go wrong? How to stretch JLabel size to parent container?

Answer 1

My problem not in JLablel. I attempted to use this in constraints but really it's not correct way. You need to get container like this:

Container contentPane = this.getContentPane();

After that you can use contentPane in constraints:

layout.putConstraint(SpringLayout.WEST, imageContainer, 5, SpringLayout.WEST, contentPane);
layout.putConstraint(SpringLayout.NORTH, imageContainer, 5, SpringLayout.NORTH, contentPane);
layout.putConstraint(SpringLayout.EAST, imageContainer, -5, SpringLayout.EAST, contentPane);
layout.putConstraint(SpringLayout.SOUTH, imageContainer, -5, SpringLayout.NORTH, filterButton);

layout.putConstraint(SpringLayout.WEST, filterButton, 5, SpringLayout.WEST, contentPane);
layout.putConstraint(SpringLayout.SOUTH, filterButton, -5, SpringLayout.SOUTH, contentPane);

And this work.