基于android4.4修改，在frameworks/base/services/java/com/android/server/power/PowerManagerService.java里，查看休眠方法goToSleep方法，发现休眠最后是调用一下方法，

private void updatePowerStateLocked() {
if (!mSystemReady || mDirty == 0) {
return;
}

// Phase 0: Basic state updates.
updateIsPoweredLocked(mDirty);
updateStayOnLocked(mDirty);

// Phase 1: Update wakefulness.
// Loop because the wake lock and user activity computations are influenced
// by changes in wakefulness.
final long now = SystemClock.uptimeMillis();
int dirtyPhase2 = 0;
for (;;) {
int dirtyPhase1 = mDirty;
dirtyPhase2 |= dirtyPhase1;
mDirty = 0;

updateWakeLockSummaryLocked(dirtyPhase1);
updateUserActivitySummaryLocked(now, dirtyPhase1);
if (!updateWakefulnessLocked(dirtyPhase1)) {
break;
}
}

// Phase 2: Update dreams and display power state.
updateDreamLocked(dirtyPhase2);
updateDisplayPowerStateLocked(dirtyPhase2);

// Phase 3: Send notifications, if needed.
if (mDisplayReady) {
sendPendingNotificationsLocked();
}

// Phase 4: Update suspend blocker.
// Because we might release the last suspend blocker here, we need to make sure
// we finished everything else first!
updateSuspendBlockerLocked();
}

红色部分注释掉以后，系统黑屏休眠时，就不会影响应用了，比如camera的使用。