学步园

JComboBox默认是不支持显示图片的，这就得自己动手重写一个JComboBox，主要重写它的UI 和ListRederer

1、addItem的显示重写，

 public class ComboBoxImageItem extends JLabel implements ListCellRenderer {</p> <p> /**<br /> *<br /> */<br /> private static final long serialVersionUID = -4164259284389215412L;</p> <p> private String path;</p> <p> public ComboBoxImageItem(String path){<br /> this.path = path;<br /> this.setOpaque(true);<br /> }<br /> /**<br /> * list - 正在绘制的 JList。<br /> * value - 由 list.getModel().getElementAt(index) 返回的值。<br /> * index - 单元格索引。<br /> * isSelected - 如果选择了指定的单元格，则为 true。<br /> * cellHasFocus - 如果指定的单元格拥有焦点，则为 true。<br /> */<br /> public Component getListCellRendererComponent(JList list, Object value,<br /> int index, boolean isSelected, boolean cellHasFocus) {<br /> if(value!=null)<br /> {<br /> setIcon(new ImageIcon(path + value));<br /> setBackground(isSelected ? Color.GRAY : Color.WHITE);<br /> setForeground(isSelected ? Color.WHITE : Color.GRAY);<br /> }<br /> return this;<br /> } </p> <p>}

2、重写JComboBox的UI

public class ComboBoxExtendsUI extends BasicComboBoxUI {</p> <p> @Override<br /> public void paint(Graphics g, JComponent c) {<br /> hasFocus = comboBox.hasFocus();<br /> if ( !comboBox.isEditable() ) {<br /> Rectangle r = rectangleForCurrentValue();<br /> paintCurrentValueBackground(g,r,hasFocus);<br /> paintCurrentValue(g,r,hasFocus);<br /> }<br /> }</p> <p> /**<br /> * 重写JComboBox的按钮<br /> */<br /> @Override<br /> protected JButton createArrowButton() {</p> <p> String path = "C:/Documents and Settings/Administrator/workspace/IQBoard/src/com/returnstar/board/resource/img/toolbar/draw/h.png";<br /> JButton button = new JButton(new ImageIcon(path));<br /> button.setName("ComboBox.arrowButton");<br /> return button;<br /> }</p> <p> @Override<br /> protected Rectangle rectangleForCurrentValue() {<br /> int width = comboBox.getWidth();<br /> int height = comboBox.getHeight();<br /> Insets insets = getInsets();<br /> int editorWidth = width - (insets.left + insets.right);<br /> int editorHeight = (height - (insets.top + insets.bottom - 1)) / 2;</p> <p> return new Rectangle(<br /> insets.left, insets.top, editorWidth, editorHeight);<br /> }</p> <p> @Override<br /> protected LayoutManager createLayoutManager() {<br /> return new LayoutM();<br /> }</p> <p> class LayoutM implements LayoutManager{</p> <p> public void addLayoutComponent(String name, Component comp) {}</p> <p> public void layoutContainer(Container parent) {</p> <p> JComboBox box = (JComboBox) parent;<br /> int width = box.getWidth();<br /> int height = box.getHeight();</p> <p> Insets insets = getInsets();</p> <p> int buttonWidth = width - (insets.left + insets.right);<br /> int buttonHeight = (height - (insets.top + insets.bottom + 2)) / 2;</p> <p> if (arrowButton != null){<br /> arrowButton.setBounds(<br /> insets.left, height - insets.bottom - buttonHeight,<br /> buttonWidth, buttonHeight);<br /> }</p> <p> if (editor != null){<br /> editor.setBounds(rectangleForCurrentValue());<br /> }<br /> }</p> <p> public Dimension minimumLayoutSize(Container parent) {<br /> return parent.getMinimumSize();<br /> }</p> <p> public Dimension preferredLayoutSize(Container parent) {<br /> return parent.getPreferredSize();<br /> }</p> <p> public void removeLayoutComponent(Component comp) {}</p> <p> }</p> <p>}

3、CustomComboBox自定义按钮

public class CustomComboBox extends JComboBox {</p> <p> /**<br /> *<br /> */<br /> private static final long serialVersionUID = -1255101315734281668L;</p> <p> public CustomComboBox(){</p> <p> this.setUI(new ComboBoxExtendsUI());</p> <p> String path = "C:/Documents and Settings/Administrator/workspace/IQBoard/src/com/returnstar/board/resource/img/toolbar/draw/";</p> <p> ComboBoxImageItem label = new ComboBoxImageItem(path);<br /> this.setRenderer(label);<br /> }<br /> }

4、main函数

public class Main {</p> <p> public static void main(String[] args) {</p> <p> JFrame jframe = new JFrame();<br /> jframe.setLayout(null);</p> <p> CustomComboBox combo = new CustomComboBox();</p> <p> combo.addItem("streak/1.png");<br /> combo.addItem("streak/2.png");<br /> combo.addItem("streak/3.png");<br /> combo.addItem("streak/4.png");<br /> combo.addItem("streak/5.png");</p> <p> combo.setBounds(100, 100, 60, 30);<br /> jframe.add(combo);</p> <p> jframe.setBounds(300, 300, 500, 400);<br /> jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);<br /> jframe.setVisible(true);<br /> }</p> <p>}<br />