屏screen_off和睡眠sleep都有对应的配置时间，如果Settings开了接口也都是可以配置的。默认情况下要看SettingsProvider里面对应的default的值，当然特定的产品要考虑到overlay的情况。
比如在这里def_screen_off_timeout则是60s，而def_sleep_timeout是-1则表示关闭了睡眠功能。换句话说，机器不用过1分钟系统会进入屏保，不会睡眠，屏幕或者hdmi是一直都有信号输出的。
/p-base/frameworks/base/packages/SettingsProvider/res/values/defaults.xml
<integer name="def_screen_off_timeout">60000</integer>
<integer name="def_sleep_timeout">-1</integer>60000 ms , 看code里面的时间都是毫秒。
overlay的情况
这里面默认的睡眠时间是20s，屏保时间是10s，也就是说没事做10s进屏保，再过10s进睡眠。
<integer name="def_sleep_timeout">20000</integer>
<integer name="def_screen_off_timeout">10000</integer>参考日志如下，uid 1000 指的是Process.SYSTEM_UID, 说明是系统发起的。
08-22 05:09:51.244 3067 3092 I PowerManagerService: Nap time (uid 1000)...
08-22 05:09:51.245 3067 3092 I DreamManagerService: Entering dreamland.
08-22 05:09:51.245 3067 3092 I PowerManagerService: Dreaming...
08-22 05:10:01.243 3067 3092 I PowerManagerService: Going to sleep due to screen timeout (uid 1000)...
08-22 05:10:01.244 3067 3092 I DreamManagerService: Gently waking up from dream.
08-22 05:10:01.245 3067 3092 I PowerManagerService: Sleeping (uid 1000)...
08-22 05:10:01.247 2892 2954 E : getRealActiveConfig to config(0).
08-22 05:10:01.248 3067 3088 I DreamManagerService: Performing gentle wake from dream.在每次更新系统power状态的时候，都要基于当前的user activity计算再次唤醒或者睡眠的时间。关键函数updateUserActivitySummaryLocked，主要是计算出下次超时时间nextTimeout和用户状态mUserActivitySummary，当满足nextTimeout到下次更新状态的时候会基于这个用户状态来进行相应的动作，是dim、dream、还是sleep。注意，这个状态的计算是逐层变深的，后面的计算如果满足条件会覆盖掉前面的计算。另一方面，整个系统进入休眠的顺序也一定是dim、dream、doze、sleep。
/**
* Updates the value of mUserActivitySummary to summarize the user requested
* state of the system such as whether the screen should be bright or dim.
* Note that user activity is ignored when the system is asleep.
*
* This function must have no other side-effects.
*/
private void updateUserActivitySummaryLocked(long now, int dirty) {
// Update the status of the user activity timeout timer.
if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY
| DIRTY_WAKEFULNESS | DIRTY_SETTINGS)) != 0) {
mHandler.removeMessages(MSG_USER_ACTIVITY_TIMEOUT);
long nextTimeout = 0;
if (mWakefulness == WAKEFULNESS_AWAKE
|| mWakefulness == WAKEFULNESS_DREAMING
|| mWakefulness == WAKEFULNESS_DOZING) {
final long sleepTimeout = getSleepTimeoutLocked();
final long screenOffTimeout = getScreenOffTimeoutLocked(sleepTimeout);
final long screenDimDuration = getScreenDimDurationLocked(screenOffTimeout);
final boolean userInactiveOverride = mUserInactiveOverrideFromWindowManager;
final long nextProfileTimeout = getNextProfileTimeoutLocked(now);
mUserActivitySummary = 0;
if (mLastUserActivityTime >= mLastWakeTime) {
nextTimeout = mLastUserActivityTime
+ screenOffTimeout - screenDimDuration;
if (now < nextTimeout) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
nextTimeout = mLastUserActivityTime + screenOffTimeout;
if (now < nextTimeout) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
if (mUserActivitySummary == 0
&& mLastUserActivityTimeNoChangeLights >= mLastWakeTime) {
nextTimeout = mLastUserActivityTimeNoChangeLights + screenOffTimeout;
if (now < nextTimeout) {
if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_BRIGHT
|| mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_VR) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else if (mDisplayPowerRequest.policy == DisplayPowerRequest.POLICY_DIM) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
if (mUserActivitySummary == 0) {
if (sleepTimeout >= 0) {
final long anyUserActivity = Math.max(mLastUserActivityTime,
mLastUserActivityTimeNoChangeLights);
if (anyUserActivity >= mLastWakeTime) {
nextTimeout = anyUserActivity + sleepTimeout;
if (now < nextTimeout) {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM;
}
}
} else {
mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM;
nextTimeout = -1;
}
}
if (mUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM && userInactiveOverride) {
if ((mUserActivitySummary &
(USER_ACTIVITY_SCREEN_BRIGHT | USER_ACTIVITY_SCREEN_DIM)) != 0) {
// Device is being kept awake by recent user activity
if (nextTimeout >= now && mOverriddenTimeout == -1) {
// Save when the next timeout would have occurred
mOverriddenTimeout = nextTimeout;
}
}
mUserActivitySummary = USER_ACTIVITY_SCREEN_DREAM;
nextTimeout = -1;
}
if (nextProfileTimeout > 0) {
nextTimeout = Math.min(nextTimeout, nextProfileTimeout);
}
if (mUserActivitySummary != 0 && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
} else {
mUserActivitySummary = 0;
}
if (DEBUG_SPEW) {
Slog.d(TAG, "updateUserActivitySummaryLocked: mWakefulness="
+ PowerManagerInternal.wakefulnessToString(mWakefulness)
+ ", mUserActivitySummary=0x" + Integer.toHexString(mUserActivitySummary)
+ ", nextTimeout=" + TimeUtils.formatUptime(nextTimeout));
}
}
}mUserActivitySummary 的取值如下，这个状态的改变需要打开PowerManagerService的debug 才好看。能看到从 0x1 -> 0x2 - >0x4 这个状态切换。
// Summarizes the user activity state.
private static final int USER_ACTIVITY_SCREEN_BRIGHT = 1 << 0;
private static final int USER_ACTIVITY_SCREEN_DIM = 1 << 1;
private static final int USER_ACTIVITY_SCREEN_DREAM = 1 << 2;updateUserActivitySummaryLocked 入口参数 now ,我们可以看到时间是系统的SYSTEM_TIME_MONOTONIC 时间，是系统启动以后流逝的时间。所有的时间操作都是相对于这个时间进行的。
获得系统睡眠超时时间，要从设定值和最小灭屏值选一个大的出来，最小灭屏值一般是10s，也就是说睡眠时间不能比最小的灭屏值还小。mSleepTimeoutSetting 是可以从设置菜单设置的，菜单 "Put device to sleep" 指定多长时间进入睡眠。
private long getSleepTimeoutLocked() {
final long timeout = mSleepTimeoutSetting;
if (timeout <= 0) {
return -1;
}
return Math.max(timeout, mMinimumScreenOffTimeoutConfig);
}在初始化updateSettingsLocked里面，从SettingsProvider读数据，如果没有设定过就是默认值。
mScreenOffTimeoutSetting = Settings.System.getIntForUser(resolver,
Settings.System.SCREEN_OFF_TIMEOUT, DEFAULT_SCREEN_OFF_TIMEOUT,
UserHandle.USER_CURRENT);
mSleepTimeoutSetting = Settings.Secure.getIntForUser(resolver,
Settings.Secure.SLEEP_TIMEOUT, DEFAULT_SLEEP_TIMEOUT,
UserHandle.USER_CURRENT);后取 系统灭屏超时时间，这个主要是选一个睡眠超时和系统灭屏时间的较小值。比如前面的是灭屏是10s，睡眠是20s，那就是10s，反之还是10s。前面的两个if里面的条件一般不满足。mScreenOffTimeoutSetting 同样也是在设置菜单里可以设置的，Screen saver菜单 -》 When to start 菜单。这里可能不同型号的机器，菜单放置的位置不一样。
private long getScreenOffTimeoutLocked(long sleepTimeout) {
long timeout = mScreenOffTimeoutSetting;
if (isMaximumScreenOffTimeoutFromDeviceAdminEnforcedLocked()) {
timeout = Math.min(timeout, mMaximumScreenOffTimeoutFromDeviceAdmin);
}
if (mUserActivityTimeoutOverrideFromWindowManager >= 0) {
timeout = Math.min(timeout, mUserActivityTimeoutOverrideFromWindowManager);
}
if (sleepTimeout >= 0) {
timeout = Math.min(timeout, sleepTimeout);
}
return Math.max(timeout, mMinimumScreenOffTimeoutConfig);
}最小灭屏值是在framework/base里面config.xml里面设定的
<integer name="config_minimumScreenOffTimeout">10000</integer>参考日志
mWakefulness从Dreaming到Dozing到Asleep，mUserActivitySummary从USER_ACTIVITY_SCREEN_DREAM到啥都没。
08-22 06:22:02.828 3064 5660 D PowerManagerService: updateUserActivitySummaryLocked: mWakefulness=Dreaming, mUserActivitySummary=0x4, nextTimeout=146181 (in 264 ms)
08-22 06:22:02.828 3064 5660 D PowerManagerService: updateDisplayPowerStateLocked: mDisplayReady=true, policy=3, mWakefulness=2, mWakeLockSummary=0x3, mUserActivitySummary=0x4, mBootCompleted=true, screenBrightnessOverride=-1, useAutoBrightness=false, mScreenBrightnessBoostInProgress=false, mIsVrModeEnabled= false, sQuiescent=false
08-22 06:22:03.093 3064 3089 D PowerManagerService: handleUserActivityTimeout
08-22 06:22:03.093 3064 3089 D PowerManagerService: updateUserActivitySummaryLocked: mWakefulness=Dreaming, mUserActivitySummary=0x0, nextTimeout=146181 (1 ms ago)
08-22 06:22:03.093 3064 3089 D PowerManagerService: updateDisplayPowerStateLocked: mDisplayReady=true, policy=3, mWakefulness=2, mWakeLockSummary=0x3, mUserActivitySummary=0x0, mBootCompleted=true, screenBrightnessOverride=-1, useAutoBrightness=false, mScreenBrightnessBoostInProgress=false, mIsVrModeEnabled= false, sQuiescent=false
08-22 06:22:03.093 3064 3089 D PowerManagerService: goToSleepNoUpdateLocked: eventTime=146182, reason=2, flags=0, uid=1000
08-22 06:22:03.093 3064 3089 I PowerManagerService: Going to sleep due to screen timeout (uid 1000)...
08-22 06:22:03.094 3064 3089 D PowerManagerService: updateWakeLockSummaryLocked: mWakefulness=Dozing, mWakeLockSummary=0x3
08-22 06:22:03.094 3064 3089 D PowerManagerService: updateUserActivitySummaryLocked: mWakefulness=Dozing, mUserActivitySummary=0x0, nextTimeout=146181 (2 ms ago)
08-22 06:22:03.094 3064 3089 D PowerManagerService: updateDisplayPowerStateLocked: mDisplayReady=true, policy=3, mWakefulness=3, mWakeLockSummary=0x3, mUserActivitySummary=0x0, mBootCompleted=true, screenBrightnessOverride=-1, useAutoBrightness=false, mScreenBrightnessBoostInProgress=false, mIsVrModeEnabled= false, sQuiescent=false
08-22 06:22:03.094 3064 3089 I DreamManagerService: Gently waking up from dream.
08-22 06:22:03.095 3064 3089 D PowerManagerService: reallyGoToSleepNoUpdateLocked: eventTime=146184, uid=1000
08-22 06:22:03.095 3064 3089 I PowerManagerService: Sleeping (uid 1000)...
08-22 06:22:03.095 3064 3089 D PowerManagerService: updateWakeLockSummaryLocked: mWakefulness=Asleep, mWakeLockSummary=0x1
08-22 06:22:03.095 3064 3089 D PowerManagerService: updateUserActivitySummaryLocked: mWakefulness=Asleep, mUserActivitySummary=0x0, nextTimeout=0 (146185 ms ago)
08-22 06:22:03.096 3064 3089 D PowerManagerService: updateDisplayPowerStateLocked: mDisplayReady=false, policy=0, mWakefulness=0, mWakeLockSummary=0x1, mUserActivitySummary=0x0, mBootCompleted=true, screenBrightnessOverride=-1, useAutoBrightness=false, mScreenBrightnessBoostInProgress=false, mIsVrModeEnabled= false, sQuiescent=false
08-22 06:22:03.096 3064 3085 I DreamManagerService: Performing gentle wake from dream.