JImageComboBox.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package com.google.security.zynamics.zylib.gui.imagecombobox;

import java.awt.Component;
import java.awt.Font;

import javax.swing.ImageIcon;
import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.ListCellRenderer;
import javax.swing.border.EmptyBorder;

public class JImageComboBox extends JComboBox<ImageElement> {

  public JImageComboBox(final ImageElement[] items) {
    super(items);

    setRenderer(new ComboBoxRenderer(JLabel.CENTER));
  }

  public JImageComboBox(final ImageElement[] items, final int labelAlignment) {
    super(items);

    if ((labelAlignment != JLabel.LEFT) && (labelAlignment != JLabel.CENTER)
        && (labelAlignment != JLabel.RIGHT)) {
      throw new IllegalArgumentException("Erorr: Label alignment in invalid.");
    }

    setRenderer(new ComboBoxRenderer(labelAlignment));
  }

  private static class ComboBoxRenderer extends JLabel implements ListCellRenderer<Object> {
    private static final long serialVersionUID = 2728401247866641230L;

    private Font uhOhFont;

    public ComboBoxRenderer(final int alignment) {
      setOpaque(true);
      setHorizontalAlignment(alignment);
      setVerticalAlignment(CENTER);

      if (alignment == JLabel.LEFT) {
        setBorder(new EmptyBorder(0, 5, 0, 0));
      }
    }

    protected void setUhOhText(final String uhOhText, final Font normalFont) {
      if (uhOhFont == null) {
        // lazily create this font
        uhOhFont = normalFont.deriveFont(Font.ITALIC);
      }

      setFont(uhOhFont);
      setText(uhOhText);
    }

    /*
     * This method finds the image and text corresponding to the selected value and returns the
     * label, set up to display the text and image.
     */
    @Override
    public Component getListCellRendererComponent(final JList<?> list, final Object value,
        final int index, final boolean isSelected, final boolean cellHasFocus) {
      final ImageElement element = (ImageElement) value;

      if (isSelected) {
        setBackground(list.getSelectionBackground());
        setForeground(list.getSelectionForeground());
      } else {
        setBackground(list.getBackground());
        setForeground(list.getForeground());
      }

      if (element == null) {
        return this;
      }

      final ImageIcon icon = element.getIcon();
      final String text = element.getObject().toString();

      setIcon(icon);

      if (icon != null) {
        setText(text);
        setFont(list.getFont());
      } else {
        setUhOhText(text + " (no image available)", list.getFont());
      }

      return this;
    }
  }
}