PowerManager.WakeLock有加锁和解锁两种状态，加锁的方式有两种，一种是永久的锁住，这样的锁除非显式的放开，是不会解锁的，所以这种锁用起来要非常的小心。第二种锁是超时锁，这种锁会在锁住后一段时间解锁。
永久锁
public void acquire() { synchronized (mToken) { acquireLocked(); } }超时锁
public void acquire(long timeout) { synchronized (mToken) { acquireLocked(); mHandler.postDelayed(mReleaser, timeout); } }当时间到达超时限定以后，执行release(),释放锁
private final Runnable mReleaser = new Runnable() { public void run() { release(); } };
在创建了PowerManager.WakeLock后，有两种机制，第一种是不计数锁机制，另一种是计数锁机制。可以通过setReferenceCounted(boolean value)来指定，一般默认为计数机制。mRefCounted 为 true 为计数锁，false为非计数锁
/** * Sets whether this WakeLock is reference counted. * <p> * Wake locks are reference counted by default. If a wake lock is * reference counted, then each call to {@link #acquire()} must be * balanced by an equal number of calls to {@link #release()}. If a wake * lock is not reference counted, then one call to {@link #release()} is * sufficient to undo the effect of all previous calls to {@link #acquire()}. * </p> * * @param value True to make the wake lock reference counted, false to * make the wake lock non-reference counted. */ public void setReferenceCounted(boolean value) { synchronized (mToken) { mRefCounted = value; } }
