s18.htm

提供给JAVA编程者图形界面卷

            import javax.swing.event.*;<br>
            import javax.swing.border.*;
            <p>public class Test extends JApplet {<br>
              private JComboBox comboBox = <br>
              new JComboBox(new Object[] {<br>
              new Item(new Object[] {Color.gray, &quot;gray&quot;}),<br>
              new Item(new Object[] {Color.orange, &quot;orange&quot;}),<br>
              new Item(new Object[] {Color.red, &quot;red&quot;}),<br>
              new Item(new Object[] {Color.blue, &quot;blue&quot;}),<br>
              new Item(new Object[] {Color.yellow, &quot;yellow&quot;}),<br>
              new Item(new Object[] {Color.magenta, &quot;magenta&quot;}),<br>
              new Item(new Object[] {Color.black, &quot;black&quot;}),<br>
              new Item(new Object[] {Color.green, &quot;green&quot;}),<br>
              new Item(new Object[] {Color.lightGray, &quot;lightGray&quot;}),<br>
              new Item(new Object[] {Color.white, &quot;white&quot;}),<br>
              });</p>
            <p> public void init() {<br>
              Container contentPane = getContentPane();</p>
            <p> comboBox.setRenderer(new ColorRendererer());<br>
              comboBox.setEditor(new ColorComboBoxEditor());<br>
              comboBox.setEditable(true);</p>
            <p> contentPane.setLayout(new FlowLayout());<br>
              contentPane.add(comboBox);<br>
              }<br>
              }<br>
              class Item {<br>
              private Color color;<br>
              private String string;</p>
            <p> public Item(Object[] array) {<br>
              color = (Color)array[0];<br>
              string = (String)array[1];<br>
              }<br>
              public Color getColor() { return color; }<br>
              public String toString() { return string; }<br>
              }<br>
              class ColorComboBoxEditor extends AbstractComboBoxEditor {<br>
              ColorIcon editorIcon = new ColorIcon();<br>
              JLabel editorLabel = new JLabel(editorIcon);</p>
            <p> Item item;</p>
            <p> JColorChooser colorChooser = new JColorChooser();<br>
              ActionListener okListener = new OKListener();<br>
              Dialog dialog = JColorChooser.createDialog(<br>
              null, // parentComponent<br>
              &quot;Choose A Color&quot;,// title<br>
              true, // modal<br>
              colorChooser,<br>
              okListener, <br>
              null); // cancel listener</p>
            <p> public ColorComboBoxEditor() {<br>
              editorLabel.setBorder(BorderFactory.createEtchedBorder());</p>
            <p> editorLabel.addMouseListener(new MouseAdapter() {<br>
              public void mousePressed(MouseEvent e) {<br>
              dialog.setVisible(true);<br>
              }<br>
              });<br>
              }<br>
              class OKListener implements ActionListener {<br>
              public void actionPerformed(ActionEvent e) {<br>
              item = <br>
              new Item(new Object[] {<br>
              colorChooser.getColor(), null});</p>
            <p> fireActionPerformed(e);<br>
              }<br>
              }<br>
              public Component getEditorComponent() {<br>
              return editorLabel;<br>
              }<br>
              public Object getItem() {<br>
              return item;<br>
              }<br>
              public void setItem(Object itemToSet) {<br>
              item = (Item)itemToSet;</p>
            <p> // cannot set the selected item in an editor's<br>
              // setItem method, or an infinite loop results</p>
            <p> editorIcon.setColor(item.getColor());<br>
              editorLabel.setText(item.toString());<br>
              }<br>
              public void selectAll() {<br>
              // from ComboBoxModel interface: nothing to select <br>
              }<br>
              }<br>
              abstract class AbstractComboBoxEditor implements ComboBoxEditor 
              {<br>
              EventListenerList listenerList = new EventListenerList();</p>
            <p> public void addActionListener(ActionListener listener) {<br>
              listenerList.add(ActionListener.class, listener);<br>
              }<br>
              public void removeActionListener(ActionListener listener) {<br>
              listenerList.remove(ActionListener.class, listener);<br>
              }<br>
              protected void fireActionPerformed(ActionEvent e) {<br>
              // Guaranteed to return a non-null array<br>
              Object[] listeners = listenerList.getListenerList();<br>
              <br>
              // Process the listeners last to first, notifying<br>
              // those that are interested in this event<br>
              for (int i = listeners.length-2; i&gt;=0; i-=2) {<br>
              if (listeners[i]==ActionListener.class) {<br>
              ((ActionListener)<br>
              listeners[i+1]).actionPerformed(e);<br>
              } <br>
              }<br>
              } <br>
              }<br>
              class ColorRendererer extends JLabel implements ListCellRenderer 
              {<br>
              private ColorIcon icon = new ColorIcon();</p>
            <p> public ColorRendererer() {<br>
              setOpaque(true);<br>
              setIcon(icon);<br>
              }<br>
              public Component getListCellRendererComponent(<br>
              JList list,<br>
              Object value,<br>
              int index,<br>
              boolean isSelected,<br>
              boolean cellHasFocus) {<br>
              Item item = (Item)value;</p>
            <p> icon.setColor(item.getColor());<br>
              setText(item.toString());</p>
            <p> if(isSelected) {<br>
              setForeground(list.getSelectionForeground());<br>
              setBackground(list.getSelectionBackground());<br>
              }<br>
              else {<br>
              setForeground(list.getForeground());<br>
              setBackground(list.getBackground());<br>
              }<br>
              return this;<br>
              }<br>
              }<br>
              class ColorIcon implements Icon {<br>
              private Color color;<br>
              private int w, h;</p>
            <p> public ColorIcon() {<br>
              this(Color.gray, 50, 15);<br>
              }<br>
              public ColorIcon(Color color, int w, int h) {<br>
              this.color = color;<br>
              this.w = w;<br>
              this.h = h;<br>
              }<br>
              public void paintIcon(Component c, Graphics g, int x, int y) {<br>
              g.setColor(Color.black);<br>
              g.drawRect(x, y, w-1, h-1);<br>
              g.setColor(color);<br>
              g.fillRect(x+1, y+1, w-2, h-2);<br>
              }<br>
              public Color getColor() {<br>
              return color;<br>
              }<br>
              public void setColor(Color color) {<br>
              this.color = color;<br>
              }<br>
              public int getIconWidth() {<br>
              return w;<br>
              }<br>
              public int getIconHeight() {<br>
              return h;<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p> 18.6.1 JComboBox属性</p>
            <p>&nbsp;</p>
            <p align="center">&nbsp;</p>
            <p> 18.6.2 JComboBox事件</p>
            <p>&nbsp;</p>
            <p align="center"><b>例18-7 处理选取事件</b></p>
            <hr noshade size="1">
            import java.awt.*;<br>
            import java.awt.event.*;<br>
            import javax.swing.*;
            <p>public class Test extends JApplet {<br>
              private JComboBox comboBox = new JComboBox();</p>
            <p> public void init() {<br>
              Container contentPane = getContentPane();</p>
            <p> comboBox.addItem(&quot;Top&quot;);<br>
              comboBox.addItem(&quot;Center&quot;);<br>
              comboBox.addItem(&quot;Bottom&quot;);</p>
            <p> contentPane.setLayout(new FlowLayout());<br>
              contentPane.add(comboBox);</p>
            <p> comboBox.addItemListener(new ItemListener() { <br>
              public void itemStateChanged(ItemEvent event) {<br>
              int state = event.getStateChange();<br>
              String item = (String)event.getItem(), s;</p>
            <p> if(event.getStateChange() == ItemEvent.SELECTED)<br>
              s = &quot; selected&quot;;<br>
              else<br>
              s = &quot; deselected&quot;;</p>
            <p> JOptionPane.showMessageDialog(<br>
              comboBox, // parent component<br>
              item + s, // message<br>
              &quot;JComboBox Selection&quot;, // title<br>
              JOptionPane.INFORMATION_MESSAGE); // type<br>
              }<br>
              });<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p align="center"><b>例18-8 处理编辑事件</b></p>
            <hr noshade size="1">
            import java.awt.*;<br>
            import java.awt.event.*;<br>
            import javax.swing.*;
            <p>public class Test extends JApplet {<br>
              private JComboBox comboBox = new JComboBox();<br>
              private ComboBoxEditor editor = comboBox.getEditor();</p>
            <p> public void init() {<br>
              Container contentPane = getContentPane();</p>
            <p> comboBox.setEditable(true);</p>
            <p> comboBox.addItem(&quot;Top&quot;);<br>
              comboBox.addItem(&quot;Center&quot;);<br>
              comboBox.addItem(&quot;Bottom&quot;);</p>
            <p> contentPane.setLayout(new FlowLayout());<br>
              contentPane.add(comboBox);</p>
            <p> editor.addActionListener(new ActionListener() {<br>
              public void actionPerformed(ActionEvent e) {<br>
              String s = (String)editor.getItem();<br>
              showStatus(&quot;Item Edited: &quot; + s);<br>
              }<br>
              });<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p>&nbsp;</p>
            <p> 18.6.3 JComboBox类总结</p>
            <p>&nbsp;</p>
            <p align="center"><b>例18-9 手工显示一个组件框的弹出式菜单</b></p>
            <hr noshade size="1">
            import javax.swing.*;<br>
            import java.awt.*;<br>
            import java.awt.event.*;
            <p>public class Test extends JApplet {<br>
              public void init() {<br>
              Container contentPane = getContentPane();<br>
              JButton button = new JButton(&quot;show popup&quot;);<br>
              final JComboBox combo = new JComboBox();</p>
            <p> combo.addItem(&quot;first item&quot;);<br>
              combo.addItem(&quot;second item&quot;);<br>
              combo.addItem(&quot;third item&quot;);<br>
              combo.addItem(&quot;fourth item&quot;);<br>
              combo.addItem(&quot;fifth item&quot;);</p>
            <p> button.addActionListener(new ActionListener() {<br>
              public void actionPerformed(ActionEvent e) {<br>
              combo.showPopup();<br>
              }<br>
              });<br>
              contentPane.setLayout(new FlowLayout());<br>
              contentPane.add(button);<br>
              contentPane.add(combo);<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p>18.6.4 AWT兼容</p>
            <p>&nbsp;</p>
            <p> 18.7 本章回顾</p>
            <p>&nbsp;</p>
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