http://hi-android.info/src/android/os/PowerManager.java.html
PowerManager类为对Android电源进行管理提供了接口。它位于android/os/PowerManager.java，但是它本身实现的东西很少，主要是调用了些更底层（C/C++）的函数.
关于如何通过PowerManager类来对Android电源进行管理请参考《PowerManager》，《Android电源管理简介》
源文件：PowerManager.java
package android.os;
import android.util.Log;
import com.android.internal.os.RuntimeInit;
public class PowerManager
{
private static final String TAG = "PowerManager";
private static final int WAKE_BIT_CPU_STRONG = 1;
private static final int WAKE_BIT_CPU_WEAK = 2;
private static final int WAKE_BIT_SCREEN_DIM = 4;
private static final int WAKE_BIT_SCREEN_BRIGHT = 8;
private static final int WAKE_BIT_KEYBOARD_BRIGHT = 16;
private static final int WAKE_BIT_PROXIMITY_SCREEN_OFF = 32;
private static final int LOCK_MASK = WAKE_BIT_CPU_STRONG
| WAKE_BIT_CPU_WEAK
| WAKE_BIT_SCREEN_DIM
| WAKE_BIT_SCREEN_BRIGHT
| WAKE_BIT_KEYBOARD_BRIGHT
| WAKE_BIT_PROXIMITY_SCREEN_OFF;
public static final int PARTIAL_WAKE_LOCK = WAKE_BIT_CPU_STRONG;
public static final int FULL_WAKE_LOCK = WAKE_BIT_CPU_WEAK | WAKE_BIT_SCREEN_BRIGHT
| WAKE_BIT_KEYBOARD_BRIGHT;
public static final int SCREEN_BRIGHT_WAKE_LOCK = WAKE_BIT_CPU_WEAK | WAKE_BIT_SCREEN_BRIGHT;
public static final int SCREEN_DIM_WAKE_LOCK = WAKE_BIT_CPU_WEAK | WAKE_BIT_SCREEN_DIM;
/**
* Wake lock that turns the screen off when the proximity sensor activates.
* Since not all devices have proximity sensors, use
* {@link #getSupportedWakeLockFlags() getSupportedWakeLockFlags()} to determine if
* this wake lock mode is supported.
*
* {@hide}
*/
public static final int PROXIMITY_SCREEN_OFF_WAKE_LOCK = WAKE_BIT_PROXIMITY_SCREEN_OFF;
/**
* Flag for {@link WakeLock#release release(int)} to defer releasing a
* {@link #WAKE_BIT_PROXIMITY_SCREEN_OFF} wakelock until the proximity sensor returns
* a negative value.
*
* {@hide}
*/
public static final int WAIT_FOR_PROXIMITY_NEGATIVE = 1;
public static final int ACQUIRE_CAUSES_WAKEUP = 0x10000000;
public static final int ON_AFTER_RELEASE = 0x20000000;
/**
* Class lets you say that you need to have the device on.
*
* <p>Call release when you are done and don‘t need the lock anymore.
*/
public class WakeLock
{
static final int RELEASE_WAKE_LOCK = 1;
Runnable mReleaser = new Runnable() {
public void run() {
release();
}
};
int mFlags;
String mTag;
IBinder mToken;
int mCount = 0;
boolean mRefCounted = true;
boolean mHeld = false;
WorkSource mWorkSource;
WakeLock(int flags, String tag)
{
switch (flags & LOCK_MASK) {
case PARTIAL_WAKE_LOCK:
case SCREEN_DIM_WAKE_LOCK:
case SCREEN_BRIGHT_WAKE_LOCK:
case FULL_WAKE_LOCK:
case PROXIMITY_SCREEN_OFF_WAKE_LOCK:
break;
default:
throw new IllegalArgumentException();
}
mFlags = flags;
mTag = tag;
mToken = new Binder();
}
/**
* Sets whether this WakeLock is ref counted.
*
* <p>Wake locks are reference counted by default.
*
* @param value true for ref counted, false for not ref counted.
*/
public void setReferenceCounted(boolean value)
{
mRefCounted = value;
}
/**
* Makes sure the device is on at the level you asked when you created
* the wake lock.
*/
public void acquire()
{
synchronized (mToken) {
if (!mRefCounted || mCount++ == 0) {
try {
mService.acquireWakeLock(mFlags, mToken, mTag, mWorkSource);
} catch (RemoteException e) {
}
mHeld = true;
}
}
}
/**
* Makes sure the device is on at the level you asked when you created
* the wake lock. The lock will be released after the given timeout.
*
* @param timeout Release the lock after the give timeout in milliseconds.
*/
public void acquire(long timeout) {
acquire();
mHandler.postDelayed(mReleaser, timeout);
}
/**
* Release your claim to the CPU or screen being on.
*
* <p>
* It may turn off shortly after you release it, or it may not if there
* are other wake locks held.
*/
public void release()
{
release(0);
}
/**
* Release your claim to the CPU or screen being on.
* @param flags Combination of flag values to modify the release behavior.
* Currently only {@link #WAIT_FOR_PROXIMITY_NEGATIVE} is supported.
*
* <p>
* It may turn off shortly after you release it, or it may not if there
* are other wake locks held.
*
* {@hide}
*/
public void release(int flags)
{
synchronized (mToken) {
if (!mRefCounted || --mCount == 0) {
try {
mService.releaseWakeLock(mToken, flags);
} catch (RemoteException e) {
}
mHeld = false;
}
if (mCount < 0) {
throw new RuntimeException("WakeLock under-locked " + mTag);
}
}
}
public boolean isHeld()
{
synchronized (mToken) {
return mHeld;
}
}
public void setWorkSource(WorkSource ws) {
synchronized (mToken) {
if (ws != null && ws.size() == 0) {
ws = null;
}
boolean changed = true;
if (ws == null) {
mWorkSource = null;
} else if (mWorkSource == null) {
changed = mWorkSource != null;
mWorkSource = new WorkSource(ws);
} else {
changed = mWorkSource.diff(ws);
if (changed) {
mWorkSource.set(ws);
}
}
if (changed && mHeld) {
try {
mService.updateWakeLockWorkSource(mToken, mWorkSource);
} catch (RemoteException e) {
}
}
}
}
public String toString() {
synchronized (mToken) {
return "WakeLock{"
+ Integer.toHexString(System.identityHashCode(this))
+ " held=" + mHeld + ", refCount=" + mCount + "}";
}
}
@Override
protected void finalize() throws Throwable
{
synchronized (mToken) {
if (mHeld) {
Log.wtf(TAG, "WakeLock finalized while still held: " + mTag);
try {
mService.releaseWakeLock(mToken, 0);
} catch (RemoteException e) {
}
}
}
}
}
public WakeLock newWakeLock(int flags, String tag)
{
if (tag == null) {
throw new NullPointerException("tag is null in PowerManager.newWakeLock");
}
return new WakeLock(flags, tag);
}
public void userActivity(long when, boolean noChangeLights)
{
try {
mService.userActivity(when, noChangeLights);
} catch (RemoteException e) {
}
}
public void goToSleep(long time)
{
try {
mService.goToSleep(time);
} catch (RemoteException e) {
}
}
/**
* sets the brightness of the backlights (screen, keyboard, button).
*
* @param brightness value from 0 to 255
*
* {@hide}
*/
public void setBacklightBrightness(int brightness)
{
try {
mService.setBacklightBrightness(brightness);
} catch (RemoteException e) {
}
}
/**
* Returns the set of flags for {@link #newWakeLock(int, String) newWakeLock()}
* that are supported on the device.
* For example, to test to see if the {@link #PROXIMITY_SCREEN_OFF_WAKE_LOCK}
* is supported:
*
* {@samplecode
* PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
* int supportedFlags = pm.getSupportedWakeLockFlags();
* boolean proximitySupported = ((supportedFlags & PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK)
* == PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK);
* }
*
* @return the set of supported WakeLock flags.
*
* {@hide}
*/
public int getSupportedWakeLockFlags()
{
try {
return mService.getSupportedWakeLockFlags();
} catch (RemoteException e) {
return 0;
}
}
public boolean isScreenOn()
{
try {
return mService.isScreenOn();
} catch (RemoteException e) {
return false;
}
}
public void reboot(String reason)
{
try {
mService.reboot(reason);
} catch (RemoteException e) {
}
}
private PowerManager()
{
}
public PowerManager(IPowerManager service, Handler handler)
{
mService = service;
mHandler = handler;
}
IPowerManager mService;
Handler mHandler;
}
注意：* {@hide}表示该方法对外部开发用户是隐藏了，Android的对外API中并不提供该方法。
只有在Android系统的framework或应用程序中才能用。