how to set color of rigidarea

Question

I have a JFrame whose background color is black.

setBackground(Color.BLACK);

I used RigidArea as filter:

Component rigidArea = Box.createRigidArea(new Dimension(0, 20));
rigidArea.setBackground(Color.BLACK);
getContentPane().add(rigidArea);

But this doesn't work, as the rigidArea's color is not black. What's wrong here?

Answer 1

您是否尝试过将JFrame内容窗格的背景设置为黑色？

getContentPane().setBackground(Color.BLACK);

Answer 2

From the docs , createRigidArea creates an invisible component that's always the specified size.

For visible components, you could create a helper method to create a JPanel:

JComponent createVisibleComponent(Dimension d) {
    JPanel panel = new JPanel();
    panel.setMinimumSize(d);
    panel.setMaximumSize(d);
    panel.setPreferredSize(d);

    return panel;
}

Answer 3

Why not simply adding a JPanel and specify its dimensions?

JPanel pan = new JPanel();
pan.setBackground(Color.BLACK);
Dimension d = new Dimension(0,20);
pan.setSize(d);
pan.setPreferredSize(d);
pan.setMaximumSize(d);
pan.setMinimumSize(d);
getContentPane().add(pan);