com.jidesoft.swing.NullPanel Maven / Gradle / Ivy

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/*
 * @(#)HollowPanel.java 7/12/2005
 *
 * Copyright 2002 - 2005 JIDE Software Inc. All rights reserved.
 */
package com.jidesoft.swing;

import javax.swing.*;
import java.awt.*;

/**
 * This is part of the null-components. A null component doesn't have
 * foreground, background or font value set. In the other words, the
 * foreground, background and font value of null-component are null.
 * But this doesn't mean getBackground(), getForeground() or getFont()
 * will return null. According to {@link java.awt.Component#getBackground()},
 * {@link java.awt.Component#getForeground()} and {@link java.awt.Component#getFont()},
 * if the value is null, it will get the value from its parent.
 * In the other words, if you add a null-component to JPanel, you can use
 * JPanel to control the background, foreground and font of this null-component.
 * The feature is very helpful if you want to make sure all components in a JPanel
 * has the same background, foreground or font.
 * 
 * We creates a few null-components. It doesn't cover all components. You can always
 * create your own. All you need to do is this
 * 

 * public class NullXxxComponent extends XxxComponent {
 *     // all the constructors
 * 
 *     public void updateUI() {
 *         super.updateUI();
 *         clearAttribute();
 *     }
 * 
 *     private void clearAttribute() {
 *         setFont(null);
 *         setBackground(null);
 *         // do not do this for JButton since JButton always paints button
 *         // content background. So it'd better to leave the foreground alone
 *         setForeground(null);
 *     }
 * }
 * 
 *
 * @see NullButton
 * @see NullCheckBox
 * @see NullJideButton
 * @see NullLabel
 * @see NullRadioButton
 */
public class NullPanel extends JPanel {
    public NullPanel() {
    }

    public NullPanel(boolean isDoubleBuffered) {
        super(isDoubleBuffered);
    }

    public NullPanel(LayoutManager layout) {
        super(layout);
    }

    public NullPanel(LayoutManager layout, boolean isDoubleBuffered) {
        super(layout, isDoubleBuffered);
    }

    @Override
    public void updateUI() {
        super.updateUI();
        clearAttribute();
    }

    private void clearAttribute() {
        setFont(null);
        setBackground(null);
        setForeground(null);
    }
}