s10.htm

提供给JAVA编程者图形界面卷

            <p> menuBar.add(fileMenu);<br>
              setJMenuBar(menuBar);<br>
              }<br>
              }<br>
              class UnderlineElement extends JButton implements MenuElement {<br>
              private boolean drawUnderline = false;</p>
            <p> public UnderlineElement(String s) {<br>
              super(s);<br>
              setBorder(BorderFactory.createEmptyBorder(2,2,2,2));<br>
              }<br>
              public Component getComponent() {<br>
              return this;<br>
              }<br>
              public MenuElement[] getSubElements() {<br>
              return new MenuElement[0];<br>
              }<br>
              public void menuSelectionChanged(boolean b) {<br>
              drawUnderline = b;<br>
              repaint();<br>
              }<br>
              public void paintComponent(Graphics g) {<br>
              super.paintComponent(g);</p>
            <p> Insets insets = getInsets();</p>
            <p> if(drawUnderline) {<br>
              FontMetrics fm = g.getFontMetrics();<br>
              g.drawLine(insets.left, insets.top + fm.getHeight(),<br>
              fm.stringWidth(getText()), <br>
              insets.top + fm.getHeight());<br>
              }<br>
              }<br>
              public void processKeyEvent(KeyEvent me,<br>
              MenuElement[] element, <br>
              MenuSelectionManager msm) {<br>
              }<br>
              public void processMouseEvent(MouseEvent me) {<br>
              super.processMouseEvent(me);<br>
              MenuSelectionManager.defaultManager().processMouseEvent(<br>
              me);<br>
              }<br>
              public void processMouseEvent(MouseEvent me, <br>
              MenuElement[] element, <br>
              MenuSelectionManager msm) {<br>
              if(me.getID() == MouseEvent.MOUSE_CLICKED || <br>
              me.getID() == MouseEvent.MOUSE_RELEASED) {</p>
            <p> msm.setSelectedPath(null);<br>
              doClick();<br>
              }<br>
              else<br>
              msm.setSelectedPath(getPath());<br>
              }<br>
              public MenuElement[] getPath() {<br>
              MenuSelectionManager defaultManager = <br>
              MenuSelectionManager.defaultManager();<br>
              MenuElement oldPath[] = defaultManager.getSelectedPath();<br>
              MenuElement newPath[];<br>
              int len = oldPath.length;</p>
            <p> if(len &gt; 0) {<br>
              MenuElement lastElement = oldPath[len-1];<br>
              Component parent = getParent();</p>
            <p> if (lastElement == parent) {<br>
              newPath = new MenuElement[len+1];</p>
            <p> System.arraycopy(oldPath, 0, newPath, 0, len);<br>
              newPath[len] = this;<br>
              }<br>
              else {<br>
              int j;</p>
            <p> for (j = len-1; j &gt;= 0; j--) {<br>
              if (oldPath[j].getComponent() == parent)<br>
              break;<br>
              }<br>
              newPath = new MenuElement[j+2];<br>
              System.arraycopy(oldPath, 0, newPath, 0, j+1);<br>
              newPath[j+1] = this;<br>
              }<br>
              }<br>
              else<br>
              return new MenuElement[0];</p>
            <p> return newPath;<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p> 10.8 JPopupMenu</p>
            <p>&nbsp;</p>
            <p align="center"><b>例10-16 使用弹出式菜单</b></p>
            <hr noshade size="1">
            import javax.swing.*;<br>
            import javax.swing.event.*;<br>
            import java.awt.*;<br>
            import java.awt.event.*;
            <p>public class Test extends JApplet {<br>
              public void init() {<br>
              Container contentPane = getContentPane();<br>
              final JLabel label = new JLabel(&quot;Click here for popup&quot;);<br>
              final JPopupMenu popup = new JPopupMenu();<br>
              final JSlider slider = new JSlider();</p>
            <p> popup.add(new JMenuItem(&quot;Copy&quot;, new ImageIcon(this.getClass().getResource(&quot;copy.gif&quot;))));<br>
              popup.add(new CutAction(new ImageIcon(this.getClass().getResource(&quot;cut.gif&quot;))));<br>
              popup.addSeparator();<br>
              popup.add(slider);</p>
            <p> label.addMouseListener(new MouseAdapter() {<br>
              public void mousePressed (MouseEvent e) { <br>
              popup.show(label, e.getX(), e.getY());<br>
              }<br>
              });<br>
              slider.addChangeListener(new ChangeListener() {<br>
              public void stateChanged(ChangeEvent e) {<br>
              if( ! slider.getValueIsAdjusting())<br>
              popup.setVisible(false);<br>
              }<br>
              });</p>
            <p> label.setHorizontalAlignment(JLabel.CENTER);<br>
              contentPane.add(label, BorderLayout.CENTER);<br>
              }<br>
              class CutAction extends AbstractAction {<br>
              java.net.URL iconurl;<br>
              <br>
              public CutAction(Icon icon) {<br>
              //super(&quot;Cut&quot;, new ImageIcon(&quot;cut.gif&quot;));<br>
              super(&quot;Cut&quot;,icon);<br>
              }<br>
              public void actionPerformed(ActionEvent e) {<br>
              System.out.println(&quot;cut&quot;);<br>
              }<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p> 10.8.1 弹出式菜单触发器</p>
            <p>&nbsp;</p>
            <p align="center"><b>例10-17 显示一个弹出式菜单以响应弹出式菜单触发器</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>
              private JPopupMenu popup = new JPopupMenu();</p>
            <p> public void init() {<br>
              Container contentPane = getContentPane();</p>
            <p> popup.add(new JMenuItem(&quot;item one&quot;));<br>
              popup.add(new JMenuItem(&quot;item two&quot;));<br>
              popup.add(new JMenuItem(&quot;item three&quot;));<br>
              popup.add(new JMenuItem(&quot;item four&quot;));</p>
            <p> contentPane.addMouseListener(new MouseAdapter() {<br>
              public void mousePressed (MouseEvent e) { <br>
              showPopup(e); <br>
              }<br>
              public void mouseClicked (MouseEvent e) { <br>
              showPopup(e); <br>
              }<br>
              public void mouseReleased(MouseEvent e) { <br>
              showPopup(e); <br>
              }<br>
              });<br>
              }<br>
              void showPopup(MouseEvent e) {<br>
              if(e.isPopupTrigger())<br>
              popup.show(this, e.getX(), e.getY());<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p> 10.8.2 轻量/中量/重量弹出式菜单</p>
            <p>&nbsp;</p>
            <p> 10.8.3 弹出式菜单调用者</p>
            <p>&nbsp;</p>
            <p align="center"><b>例10-18 相对于其调用者显示弹出式菜单</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>
              JComboBox combobox = new JComboBox();<br>
              JPopupMenu popup = new JPopupMenu();<br>
              ColoredCanvas popupRelativeToMe;<br>
              ColoredCanvas blueCanvas, redCanvas, yellowCanvas;</p>
            <p> public void init() {<br>
              Container contentPane = getContentPane();<br>
              blueCanvas = new ColoredCanvas(Color.blue);<br>
              redCanvas = new ColoredCanvas(Color.red);<br>
              yellowCanvas = new ColoredCanvas(Color.yellow);<br>
              popupRelativeToMe = blueCanvas;</p>
            <p> popup.add(new JMenuItem(&quot;item one&quot;));<br>
              popup.add(new JMenuItem(&quot;item two&quot;));<br>
              popup.add(new JMenuItem(&quot;item three&quot;));<br>
              popup.add(new JMenuItem(&quot;item four&quot;));</p>
            <p> contentPane.setLayout(new FlowLayout());<br>
              contentPane.add(new JLabel(&quot;Popup Over:&quot;));<br>
              contentPane.add(combobox); <br>
              contentPane.add(blueCanvas);<br>
              contentPane.add(redCanvas);<br>
              contentPane.add(yellowCanvas);</p>
            <p> combobox.addItem(&quot;Blue Canvas&quot;);<br>
              combobox.addItem(&quot;Yellow Canvas&quot;);<br>
              combobox.addItem(&quot;Red Canvas&quot;);</p>
            <p> combobox.addItemListener(new ItemListener() {<br>
              public void itemStateChanged(ItemEvent event) {<br>
              if(event.getStateChange() == ItemEvent.SELECTED) {<br>
              JComboBox c = (JComboBox)event.getSource();<br>
              String label = (String)c.getSelectedItem();</p>
            <p> if(label.equals(&quot;Blue Canvas&quot;))<br>
              popupRelativeToMe = blueCanvas;<br>
              else if(label.equals(&quot;Red Canvas&quot;))<br>
              popupRelativeToMe = redCanvas;<br>
              else if(label.equals(&quot;Yellow Canvas&quot;))<br>
              popupRelativeToMe = yellowCanvas;</p>
            <p> popup.show(popupRelativeToMe, 5, 5);<br>
              }<br>
              }<br>
              });<br>
              }<br>
              }<br>
              class ColoredCanvas extends JPanel {<br>
              private Color color;</p>
            <p> public ColoredCanvas(Color color) {<br>
              this.color = color;<br>
              }<br>
              public void paintComponent(Graphics g) {<br>
              super.paintComponent(g);</p>
            <p> Dimension size = getSize();<br>
              g.setColor (color);<br>
              g.fill3DRect(0,0,size.width-1,size.height-1,true);<br>
              }<br>
              public Dimension getPreferredSize() {<br>
              return new Dimension(100,100);<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p> 10.8.4 JPopupMenu属性</p>
            <p>&nbsp;</p>
            <p> 10.8.5 JPopupMenu事件</p>
            <p>&nbsp;</p>
            <p align="center"><b>例10-19 弹出式菜单事件的清单</b></p>
            <hr noshade size="1">
            import javax.swing.*;<br>
            import javax.swing.event.*;<br>
            import java.awt.*;<br>
            import java.awt.event.*;<br>
            import java.beans.*;
            <p>public class Test extends JApplet {<br>
              public void init() {<br>
              final Container contentPane = getContentPane();<br>
              final JPopupMenu popup = new JPopupMenu();<br>
              <br>
              popup.add(new JMenuItem(&quot;item one&quot;));<br>
              popup.add(new JMenuItem(&quot;item two&quot;));<br>
              popup.add(new JMenuItem(&quot;item three&quot;));<br>
              popup.add(new JMenuItem(&quot;item four&quot;));</p>
            <p> popup.addPopupMenuListener(new PopupMenuListener() {<br>
              public void popupMenuCanceled(PopupMenuEvent e) {<br>
              showStatus(&quot;menu canceled&quot;);<br>
              }<br>
              public void popupMenuWillBecomeVisible(<br>
              PopupMenuEvent e) {<br>
              showStatus(&quot;menu will become visible&quot;);<br>
              }<br>
              public void popupMenuWillBecomeInvisible(<br>
              PopupMenuEvent e) {<br>
              showStatus(&quot;menu will become invisible&quot;);<br>
              }<br>
              });<br>
              addMouseListener(new MouseAdapter() {<br>
              public void mousePressed (MouseEvent e) { <br>
              popup.show(contentPane, e.getX(), e.getY());<br>
              }<br>
              });<br>
              }<br>
              }</p>
            <hr size="1" noshade>
            <p> 10.8.6 JPopupMenu类总结</p>
            <p>&nbsp;</p>
            <p align="center"><b>例10-20 为弹出式菜单设置位置、边框和调用者</b></p>
            <hr noshade size="1">
            import javax.swing.*;<br>
            import java.awt.*;<br>
            import java.awt.event.*;