文章转载自:http://blog.youkuaiyun.com/hzdysymbol/archive/2009/03/19/4004791.aspx<wbr style="line-height:25px"><wbr style="line-height:25px"><div style="line-height:25px"><span style="line-height:28px; font-size:19px; font-family:'Times New Roman'"> <span style="line-height:34px">Android Power Management</span></span></div> <div style="line-height:25px"><span style="line-height:21px; font-family:verdana,sans-serif"><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px"><span style="line-height:18px; font-family:'Times New Roman'"></span></span></span><span style="line-height:18px; font-size:9pt; font-family:宋体">总体上来说</span><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'">Android</span></span><span style="line-height:18px; font-size:9pt; font-family:宋体">的电源管理还是比较简单的</span><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'">,</span></span><span style="line-height:18px; font-size:9pt; font-family:宋体">主要就是通过锁和定时器来切换系统的状态</span><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'">,</span></span><span style="line-height:18px; font-size:9pt; font-family:宋体">使系统的功耗降至最低</span><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'">,</span></span><span style="line-height:18px; font-size:9pt; font-family:宋体">整个系统的电源管理架构图如下</span><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'">: (</span></span><span style="line-height:18px; font-size:9pt; font-family:宋体">注该图来自</span><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'">Steve Guo)</span></span></span></div> <div style="line-height:25px"> <span style="line-height:21px; font-family:verdana,sans-serif"><span lang="EN-US" style="line-height:18px; font-size:9pt"><span style="line-height:18px; font-family:'Times New Roman'"></span></span></span> <div style="line-height:21px"><img alt="电源管理简介(上) - hubingforever - 民主与科学" src="https://p-blog.youkuaiyun.com/images/p_blog_youkuaiyun.com/hzdysymbol/EntryImages/20090319/block%20diagram.JPG" style="line-height:21px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; max-width:100%; margin-top:0px; margin-right:10px; margin-bottom:0px; margin-left:0px"></div> </div> </wbr></wbr>
接下来我们从Java应用层面, Android framework层面, Linux内核层面分别进行详细的讨论:
应用层的使用:
Android提供了现成android.os.PowerManager类,该类用于控制设备的电源状态的切换.
该类对外有三个接口函数:
void goToSleep(long time); //强制设备进入Sleep状态
Note:
尝试在应用层调用该函数,却不能成功,出现的错误好象是权限不够,但在Framework下面的Service里调用是可以的.
newWakeLock(int flags, String tag);//取得相应层次的锁
flags参数说明:
PARTIAL_WAKE_LOCK: Screen off, keyboard light off
SCREEN_DIM_WAKE_LOCK: screen dim, keyboard light off
SCREEN_BRIGHT_WAKE_LOCK: screen bright, keyboard light off
FULL_WAKE_LOCK: screen bright, keyboard bright
ACQUIRE_CAUSES_WAKEUP:一旦有请求锁时强制打开Screen和keyboard light
ON_AFTER_RELEASE:在释放锁时reset activity timer
Note:
如果申请了partial wakelock,那么即使按Power键,系统也不会进Sleep,如Music播放时
如果申请了其它的wakelocks,按Power键,系统还是会进Sleep
void userActivity(long when, boolean noChangeLights);//User activity事件发生,设备会被切换到Full on的状态,同时Reset Screen off timer.
Sample code:
PowerManager pm = (PowerManager)getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock (PowerManager.SCREEN_DIM_WAKE_LOCK, “My Tag”);
wl.acquire();
…….
wl.release();
Note:
1.在使用以上函数的应用程序中,必须在其Manifest.xml文件中加入下面的权限:
<uses-permission android:name="android.permission.WAKE_LOCK"/>
<uses-permission android:name="android.permission.DEVICE_POWER"/>
2.所有的锁必须成对的使用,如果申请了而没有及时释放会造成系统故障.如申请了partial wakelock,而没有及时释放,那系统就永远进不了Sleep模式.
注意:关于PowerManager的详细内容请参照《PowerManager》
Android Framework层面:
其主要代码文件如下:
frameworks\base\core\java\android\os\PowerManager.java
frameworks\base\services\java\com\android\server\PowerManagerService.java
frameworks\base\core\java\android\os\Power.java
frameworks\base\core\jni\android_os_power.cpp
hardware\libhardware\power\power.c
其中PowerManagerService.java是核心, Power.java提供底层的函数接口,与JNI层进行交互, JNI层的代码主要在文件android_os_Power.cpp中,与Linux kernel交互是通过Power.c来实现的, Andriod跟Kernel的交互主要是通过sys文件的方式来实现的,具体请参考Kernel层的介绍.
这一层的功能相对比较复杂,比如系统状态的切换,背光的调节及开关,Wake Lock的申请和释放等等,但这一层跟硬件平台无关,而且由Google负责维护,问题相对会少一些,有兴趣的朋友可以自己查看相关的代码.