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32.7 电源事件
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C#高级编程（第3版）【全文连载】
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32.7 电源事件
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2006-10-13 14:41:00
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<div style='float:left;width:49%'>·<a href='100165811.htm'>32.6.1 交互式服务</a></div><div style='float:right;width:49%'>·<a href='100165812.htm'>32.6.2 事件日志</a></div><div style='float:left;width:49%'>·<a href='100165813.htm'>32.6.3 性能监视</a></div><div style='float:right;width:49%'>·<a href='100165815.htm'>32.8 小结</a></div><div style='float:left;width:49%'>·<a href='100165816.htm'>4.1 继承的类型</a></div><div style='float:right;width:49%'>·<a href='100165817.htm'>4.2 实现的继承</a></div></div>
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<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style='margin-top:11.4pt;margin-right:0cm;FTEL:11.4pt;margin-left:
0cm'><a FTEL="_Toc507815593"><span lang=EN-US>32.7 </span></a><span
style='font-family:楷体_GB2312'>电源事件</span></h3>
<p class=MsoNormal><span style='font-family:宋体'>从</span><span lang=EN-US>Windows
2000</span><span style='font-family:宋体'>开始，服务就可以响应电源的变化了。<span
style='color:black'>例如，系统可以休眠，在系统休眠时，内存中的内容保存到硬盘上，这样，系统的启动速度就会比较快。此外，为了减少电源的消耗，</span></span><span
lang=EN-US style='color:black'>Windows 2000</span><span style='font-family:
宋体;color:black'>还支持系统等待，但是，在需要时系统可以自动唤醒。</span></p>
<p class=MsoNormal><span style='font-family:宋体'>对于所有的电源事件而言，服务可以接收带有附加参数的控制代码</span><span
lang=EN-US>SERVICE_CONTROL _POWEREVENT</span><span style='font-family:宋体'>。在参数中可以找到事件的原因，事件的原因可以是电池没电了、系统正处于等待状态或电源状态改变了等等。根据事件的原因，服务将作出不同的反应，例如服务减慢、等待背景线程、关闭网络连接和关闭文件等。</span></p>
<p class=MsoNormal><span lang=EN-US>System.ServiceProcess</span><span
style='font-family:宋体'>命名空间中的类也支持电源事件。使用</span><span lang=EN-US>CanPauseAnd
Continue</span><span style='font-family:宋体'>属性，可以把服务配置为响应暂停事件和继续事件。也可以为电源管理设置</span><span
lang=EN-US>CanHandlePowerEvent</span><span style='font-family:宋体'>属性。使用</span><span
lang=EN-US>Win32 API</span><span style='font-family:宋体'>方法</span><span
lang=EN-US>RegisterServiceCtrlHandlerEx()</span><span style='font-family:宋体'>，可以在</span><span
lang=EN-US>SCM</span><span style='font-family:宋体'>中注册处理电源事件的</span><span
lang=EN-US>Windows 2000</span><span style='font-family:宋体'>服务。</span></p>
<p class=MsoNormal><span style='font-family:宋体;color:black'>如果</span><span
lang=EN-US style='color:black'>CanHandlePowerEvent</span><span
style='font-family:宋体;color:black'>属性的值为</span><span lang=EN-US
style='color:black'>true</span><span style='font-family:宋体;color:black'>，就会调用</span><span
lang=EN-US style='color:black'>ServiceBase</span><span style='font-family:宋体;
color:black'>类的</span><span lang=EN-US style='color:black'>OnPowerEvent()</span><span
style='font-family:宋体;color:black'>方法。可以重写这个方法，接收电源事件，根据服务的执行情况进行响应。电源事件的原因被传送给</span><span
lang=EN-US>PowerBroadcastStatus</span><span style='font-family:宋体;color:black'>类型的参数。这个枚举的值如</span><span
style='font-family:宋体'>表</span><span lang=EN-US>32-7</span><span
style='font-family:宋体'>所示<span style='color:black'>。</span></span></p>
<p class=a5 style='margin-top:8.15pt'><span style='font-family:黑体;color:black'>表</span><span
lang=EN-US style='color:black'> 32-7</span></p>
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<table class=MsoNormalTable border=1 cellspacing=0 cellpadding=0 width=586
style='width:439.75pt;margin-left:14.2pt;border-collapse:collapse;border:none'>
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<td width=174 valign=top style='width:130.7pt;border:solid windowtext 1.0pt;
border-left:none;padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a2><span lang=EN-US style='color:black'>PowerStatus</span><span
style='font-family:黑体;color:black'>的值</span></p>
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<td width=412 valign=top style='width:309.05pt;border-top:solid windowtext 1.0pt;
border-left:none;border-bottom:solid windowtext 1.0pt;border-right:none;
padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a2><span style='font-family:黑体;color:black'>描</span><span
lang=EN-US style='color:black'> </span><span
style='font-family:黑体;color:black'>述</span></p>
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<td width=174 valign=top style='width:130.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span lang=EN-US style='color:black'>BatteryLow</span></p>
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solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span style='font-family:宋体;
color:black'>电池没有电了，应该把服务的功能降低到最小的程度</span></p>
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<td width=174 valign=top style='width:130.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span lang=EN-US style='color:black'>PowerStatusChange</span></p>
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solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span style='font-family:宋体;
color:black'>电池电源的开关</span><span lang=EN-US style='color:black'>A/C</span><span
style='font-family:宋体;color:black'>进行了切换，或者电池电源低于一定的阙值等</span></p>
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<td width=174 valign=top style='width:130.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span lang=EN-US style='color:black'>QuerySuspend</span></p>
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solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span style='font-family:宋体;
color:black'>系统请求进入挂起模式。可以拒绝这样的请求，也可以为进入挂起模式做一些工作，例如关闭文件和断开网络连接等</span></p>
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<td width=174 valign=top style='width:130.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span lang=EN-US style='color:black'>QuerySuspendFailed</span></p>
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<td width=412 valign=top style='width:309.05pt;border:none;border-bottom:
solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span style='font-family:宋体;
color:black'>把系统变为挂起模式的请求被拒绝，可以继续以前的工作</span></p>
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<td width=174 valign=top style='width:130.7pt;border-top:none;border-left:
none;border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span lang=EN-US style='color:black'>Suspend</span></p>
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<td width=412 valign=top style='width:309.05pt;border:none;border-bottom:
solid windowtext 1.0pt;padding:0cm 5.4pt 0cm 5.4pt'>
<p class=a4 style='margin-left:10.7pt'><span style='font-family:宋体;
color:black'>没有人拒绝进入挂起模式。系统不久将处于挂起模式下</span><span lang=EN-US
style='color:black'> </span></p>
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<div style='float:left;width:49%'>·<a href='100165811.htm'>32.6.1 交互式服务</a></div><div style='float:right;width:49%'>·<a href='100165812.htm'>32.6.2 事件日志</a></div><div style='float:left;width:49%'>·<a href='100165813.htm'>32.6.3 性能监视</a></div><div style='float:right;width:49%'>·<a href='100165815.htm'>32.8 小结</a></div><div style='float:left;width:49%'>·<a href='100165816.htm'>4.1 继承的类型</a></div><div style='float:right;width:49%'>·<a href='100165817.htm'>4.2 实现的继承</a></div></div>
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