原文的出处:http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/systemtray/我并没有全文照译.其中介绍什么是托盘的部分略去了在译后,加了一个自己写的例子.
访问系统托盘类java.awt.SystemTray代表了桌面的系统托盘.你可以通过静态方法SystemTray.getSystemTray()来进行访问.但是,在这之前,你的程序应该用静态方法SystemTray.isSupported()来测试一下系统是否支持托盘.如果系统托盘不存在或者系统不支持托盘,isSupported()将返回flase.在这种情况下调用getSysemTray的话,它将抛出java.lang.UnsupportedOperationException.每个java应用程序都只有一个单一的SystemTray实例.所以,一个程序不能创建只属于它自己的SystemTray实例;而它必须用getSystemTray()方法来取得已有的那个.SystemTray包含有一个或多个TrayIcon.通过SystemTray的方法add(java.awt.TrayIcon)方法可以添加一个TrayIcon到托盘,通过remove(java.awt.TrayIcon)将一个TrayIcon从托盘移除.注意最近添加的测试代码指明,如操作系统或者Java runtime不添加TrayIcon到托盘,add()方法可能会抛出AWTException.例如,在X-Windows中,如果托盘不存在,它将抛出AWTException下面的代码演示了如果访问系统托盘:
final TrayIcon trayIcon; if (SystemTray.isSupported()) { SystemTray tray = SystemTray.getSystemTray(); Image image = Toolkit.getDefaultToolkit().getImage( " tray.gif " ); MouseListener mouseListener = new MouseListener() { public void mouseClicked(MouseEvent e) { System.out.println( " Tray Icon - Mouse clicked! " ); } public void mouseEntered(MouseEvent e) { System.out.println( " Tray Icon - Mouse entered! " ); } public void mouseExited(MouseEvent e) { System.out.println( " Tray Icon - Mouse exited! " ); } public void mousePressed(MouseEvent e) { System.out.println( " Tray Icon - Mouse pressed! " ); } public void mouseReleased(MouseEvent e) { System.out.println( " Tray Icon - Mouse released! " ); } }; ActionListener exitListener = new ActionListener() { public void actionPerformed(ActionEvent e) { System.out.println( " Exiting... " ); System.exit( 0 ); } }; PopupMenu popup = new PopupMenu(); MenuItem defaultItem = new MenuItem( " Exit " ); defaultItem.addActionListener(exitListener); popup.add(defaultItem); trayIcon = new TrayIcon(image, " Tray Demo " , popup); ActionListener actionListener = new ActionListener() { public void actionPerformed(ActionEvent e) { trayIcon.displayMessage( " Action Event " , " An Action Event Has Been Peformed! " , TrayIcon.MessageType.INFO); } }; trayIcon.setImageAutoSize( true ); trayIcon.addActionListener(actionListener); trayIcon.addMouseListener(mouseListener); try { tray.add(trayIcon); } catch (AWTException e) { System.err.println( " TrayIcon could not be added. " ); }} else { // 不支持系统托盘 }实现Tray Icon系统托盘允许一个或多个java.awt.TrayIcon添加到它或从它移除:一个TrayIcon对象代表着一个可以添加到系统托盘的托盘图标.但是,TrayIcon的功能不止是一个显示在托盘里的图标.它还可以有工具提示(tooltip),有一个AWT的弹出菜单,还有一系列相关的侦听器 一个TrayIcon会产生各种各样的MouseEvent(pressed,released,和clicked).可以对它添加相关的侦听器去接收这些事件的通知.但是要注意,在MouseEvent从TrayIcon接收到的坐标是相对于屏幕而不是TrayIcon它自己的.TrayIcon它自己处理这些事件.例如,默认情况下,当右击TrayIcon时,和它相关的弹出菜单就会显示.当鼠标在它上面停留时,工具提示就会出现.TrayIcon也可以产生ActionEvent.在一些平台上,ActionEvent产生于用户通过鼠标或键盘选择该TrayIcon时.一个实现良好的TrayIcon应该用不同的方法去显示弹出菜单和选择托盘图标.注意,根据最新的javadocs,当一个鼠标事件被发送到它的侦听器时,它的component属性(通过父类ComponentEvent.getComponent()获取)将会被设置为null.而source属性(通过EventObject.getSource()获取)将被设置为该TrayIcon有用的特点用setImage()方法可以在以后更新TrayIcon的图标: trayIcon.setImage(updatedImage);同样你可以更新工具提示: trayIcon.setTooltip("I'm busy. Go away.");TrayIcon有一个非常有用的自动调整大小的属性.这个属性决定是否自动调整图片的大小以适应托盘的大小.默认这个属性是false的.如果图片的大小不适合托盘的大小,图片仍会以它原来的大小绘制到托盘上.也就是说,如果图片比分配的托盘空间大,图片将被剪切.另一方面,如果自动调整大小被设为true,那么图片将伸缩以适应托盘图标的大小 trayIcon.setImageAutoSize(true);最后,如果你想偶尔用工具提示通知用户程序的一些变化,你可以用displayMessage()方法.这个方法弹出一个在托盘图标上弹出一个消息.这个消息会在一段时间之后,或者用户单击它之后消失.单击它的时候,根据系统的情况,会产生ActionEvent trayIcon.displayMessage("Finished downloading", "Your Java application has finished downloading", TrayIcon.MessageType.INFO);第一个参数是标题.它通常在弹出消息里会以粗体显示.第二个参数是要显示的消息.最后,最后一个参数是TrayIcon的一个枚举类型TrayIcon.Message,有四个选择.这些选项可以用作决定在显示消息时,是否应执行某些图形操作或其他系统动作.四个选择如下:TrayIcon.MessageType.ERROR An error message TrayIcon.MessageType.INFO An information message TrayIcon.MessageType.NONE A simple message TrayIcon.MessageType.WARNING A warning message ===================================================下面是我自己写的例子
package blog.swing; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import java.awt.event.MouseListener; import java.awt.event.MouseEvent; import java.awt.PopupMenu; import java.awt.MenuItem; import java.awt.Image; import java.awt.AWTException; import java.awt.Toolkit; import java.awt.SystemTray; import java.awt.TrayIcon; import java.text.SimpleDateFormat; import java.util.Calendar; class SystemTrayDemo { SystemTray systemTray; TrayIcon trayIcon; Image trayImage; String trayTip; PopupMenu trayPopupMenu; MenuItem trayMenuItem; ActionListener trayActionListener; ActionListener menuActionListener; MouseListener trayMouseListener; Thread displayTime; public SystemTrayDemo() { if ( SystemTray.isSupported() ){ trayMouseListener = new MouseListener() { public void mouseClicked(MouseEvent e) { System.out.println( " Tray Icon - Mouse clicked! " ); } public void mouseEntered(MouseEvent e) { System.out.println( " Tray Icon - Mouse entered! " ); } public void mouseExited(MouseEvent e) { System.out.println( " Tray Icon - Mouse exited! " ); } public void mousePressed(MouseEvent e) { System.out.println( " Tray Icon - Mouse pressed! " ); } public void mouseReleased(MouseEvent e) { System.out.println( " Tray Icon - Mouse released! " ); } }; trayActionListener = new ActionListener(){ public void actionPerformed( ActionEvent e ){ System.out.println( " Tray Icon - Action event happened! " );; } }; menuActionListener = new ActionListener(){ public void actionPerformed( ActionEvent e ){ System.exit( 0 ); } }; trayPopupMenu = new PopupMenu(); trayMenuItem = new MenuItem( " exit " ); trayMenuItem.addActionListener( menuActionListener ); trayPopupMenu.add( trayMenuItem ); trayTip = " This is a SystemTray Demo " ; trayImage = Toolkit.getDefaultToolkit().getImage( " images/leaf.gif " ); trayIcon = new TrayIcon( trayImage,trayTip,trayPopupMenu ); trayIcon.addActionListener( trayActionListener ); trayIcon.addMouseListener( trayMouseListener ); trayIcon.setImageAutoSize( true ); systemTray = SystemTray.getSystemTray(); try { systemTray.add( trayIcon ); } catch ( AWTException e ){ e.printStackTrace(); } } else { System.out.println( " SystemTray unsupported! " ); } displayTime = new Thread( new Runnable(){ public void run(){ Calendar now; SimpleDateFormat sdf = new SimpleDateFormat( " yyyy-MM-dd hh:mm:ss " ); String time; while ( true ){ now = Calendar.getInstance(); time = sdf.format( now.getTime() ); trayIcon.displayMessage( " 报时 " ,time,TrayIcon.MessageType.INFO); try { Thread.sleep( 60000 ); } catch ( InterruptedException e ){ e.printStackTrace(); } } } }); displayTime.start(); } public static void main(String[] args) { new SystemTrayDemo(); }}
