前言
PowerManagerService之亮屏流程分析 归纳了亮屏/灭屏的通用流程，PowerManagerService之手动灭屏 对手动灭屏流程进行了整体的分析。 本文以前两篇文章为基础，来分析自动灭屏，请读者务必仔细阅读前两篇文章。
自动灭屏
要想分析自动灭屏，需得回顾下 PowerManagerService之亮屏流程分析 的亮屏逻辑的一些细节。
在亮屏的时候，会保存亮屏的时间，以及用户行为的时间，这两个时间用于决定用户行为，如下
// PowerManagerService.java
private void updateUserActivitySummaryLocked(long now, int dirty) {
// ...
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
// mLastWakeTime 表示上次亮屏的时间
// lastUserActivityTime 表示上次用户行为的时间
if (lastUserActivityTime >= mLastWakeTime) {
// 计算使屏幕变暗的超时时间
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
// ...
}
}
// ...
}
// ...
}
此时得到的用户行为是 USER_ACTIVITY_SCREEN_BRIGHT，表明用户行为是要点亮屏幕。
之后会向 DisplayManagerService 发起请求，而最终决定屏幕状态(亮、灭、暗，等等)的请求策略，它的更新过程如下
int getDesiredScreenPolicyLocked(int groupId) {
final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
final int wakeLockSummary = mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId);
if (wakefulness == WAKEFULNESS_ASLEEP || sQuiescent) {
// ...
} else if (wakefulness == WAKEFULNESS_DOZING) {
// ...
}
if (mIsVrModeEnabled) {
// ...
}
if ((wakeLockSummary & WAKE_LOCK_SCREEN_BRIGHT) != 0
|| !mBootCompleted
|| (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId)
& USER_ACTIVITY_SCREEN_BRIGHT) != 0
|| mScreenBrightnessBoostInProgress) {
return DisplayPowerRequest.POLICY_BRIGHT;
}
// ...
}
由于用户行为是 USER_ACTIVITY_SCREEN_BRIGHT，因此策略为 DisplayPowerRequest.POLICY_BRIGHT，它最终导致屏幕变亮。
那么亮屏后，是如何自动灭屏呢？
// PowerManagerService.java
private void updateUserActivitySummaryLocked(long now, int dirty) {
// ...
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
if (lastUserActivityTime >= mLastWakeTime) {
// 使屏幕变暗的超时时间
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
// ...
}
}
// ...
}
// 使用屏幕变暗的超时时间，发送一个定时消息来更新用户行为
if (hasUserActivitySummary && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
}
private void scheduleUserInactivityTimeout(long timeMs) {
final Message msg = mHandler.obtainMessage(MSG_USER_ACTIVITY_TIMEOUT);
msg.setAsynchronous(true);
// 利用超时时间，发送一个定时消息，更新用户行为
// 最终调用 handleUserActivityTimeout
mHandler.sendMessageAtTime(msg, timeMs);
}
private void handleUserActivityTimeout() { // runs on handler thread
synchronized (mLock) {
// 标记用户行为需要更新
mDirty |= DIRTY_USER_ACTIVITY;
// 重新更新电源状态，其实就是为了更新用户行为
updatePowerStateLocked();
}
}
从上面的代码逻辑可以看出，当 Power 键亮屏后，会计算出使屏幕变暗的超时时间，然后利用这个超时时间，发送了一个定时消息，当屏幕变暗的超时时间到了，就会再次更新用户行为，如下
// PowerManagerService.java
private void updateUserActivitySummaryLocked(long now, int dirty) {
// ...
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
if (lastUserActivityTime >= mLastWakeTime) {
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) {
// ...
} else {
// 计算灭屏的超时时间
groupNextTimeout = lastUserActivityTime + screenOffTimeout;
if (now < groupNextTimeout) { // 进入 DIM 时间段
// 更新用户行为
groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
// ...
}
// ...
// 使用灭屏的超时时间，发送一个定时消息来更新用户行为
if (hasUserActivitySummary && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
}
此次用户行为的更新，计算的是灭屏的超时时间，然后用户行为更新为 USER_ACTIVITY_SCREEN_DIM，表示用户行为要使屏幕变暗。最后利用灭屏的超时时间，发送了一个定时消息来再次更新用户行为。
现在用户行为是使屏幕变暗，再看看请求策略是如何更新的
int getDesiredScreenPolicyLocked(int groupId) {
final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
final int wakeLockSummary = mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId);
if (wakefulness == WAKEFULNESS_ASLEEP || sQuiescent) {
// ...
} else if (wakefulness == WAKEFULNESS_DOZING) {
// ...
}
if (mIsVrModeEnabled) {
// ...
}
if ((wakeLockSummary & WAKE_LOCK_SCREEN_BRIGHT) != 0
|| !mBootCompleted
|| (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId)
& USER_ACTIVITY_SCREEN_BRIGHT) != 0
|| mScreenBrightnessBoostInProgress) {
// ...
}
return DisplayPowerRequest.POLICY_DIM;
}
请求策略更新为 DisplayPowerRequest.POLICY_DIM，最终它会使屏幕变暗。
当灭屏的超时时间到了，我们看下再次更新用户行为时，会发生什么
// PowerManagerService.java
private void updateUserActivitySummaryLocked(long now, int dirty) {
// ...
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
if (lastUserActivityTime >= mLastWakeTime) {
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
groupNextTimeout = lastUserActivityTime + screenOffTimeout;
if (now < groupNextTimeout) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
// 灭屏超时前，带有 PowerManager.ON_AFTER_RELEASE 这个flag的唤醒锁释放，延长屏幕的亮/暗的时间
if (groupUserActivitySummary == 0
&& lastUserActivityTimeNoChangeLights >= mLastWakeTime) {
// ...
}
// 灭屏超时，允许进入屏保
if (groupUserActivitySummary == 0) {
// ...
}
// 按键 KeyEvent.KEYCODE_SOFT_SLEEP 进入屏保
if (groupUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM
&& userInactiveOverride) {
// ...
}
// 用 AttentionDetector 重新计算超时时间，目前不分析
if ((groupUserActivitySummary & USER_ACTIVITY_SCREEN_BRIGHT) != 0
&& (mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId)
& WAKE_LOCK_STAY_AWAKE) == 0) {
// ...
}
// 确定是否有用户行为
hasUserActivitySummary |= groupUserActivitySummary != 0;
// 保存超时时间
if (nextTimeout == -1) {
nextTimeout = groupNextTimeout;
} else if (groupNextTimeout != -1) {
nextTimeout = Math.min(nextTimeout, groupNextTimeout);
}
}
// DisplayGroupPowerStateMapper 保存用户行为
mDisplayGroupPowerStateMapper.setUserActivitySummaryLocked(groupId,
groupUserActivitySummary);
}
final long nextProfileTimeout = getNextProfileTimeoutLocked(now);
if (nextProfileTimeout > 0) {
nextTimeout = Math.min(nextTimeout, nextProfileTimeout);
}
// 利用超时时间，发送一个定时消息
if (hasUserActivitySummary && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
}
可以看到灭屏超时时间到了时，有很多因素会再次影响用户行为和超时时间，我们忽略这些因素，因此超时时间和用户行为都为0。 既然没有了用户行为和超时时间，那么自然不会发送定时消息来更新用户行为了，因为马上就要灭屏的嘛，就没必要去定时更新用户行为了。
此时，我要提醒大家，从亮屏到自动灭屏的过程中，此时 wakefulness 还是 WAKEFULNESS_AWAKE，现在马上要灭屏了，因此需要再次更新 wakefulness，这就是更新电源状态过程中，updateWakefulnessLocked() 做的
// PowerManagerService.java
private boolean updateWakefulnessLocked(int dirty) {
boolean changed = false;
if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_BOOT_COMPLETED
| DIRTY_WAKEFULNESS | DIRTY_STAY_ON | DIRTY_PROXIMITY_POSITIVE
| DIRTY_DOCK_STATE | DIRTY_ATTENTIVE | DIRTY_SETTINGS
| DIRTY_SCREEN_BRIGHTNESS_BOOST)) != 0) {
final long time = mClock.uptimeMillis();
for (int id : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(id) == WAKEFULNESS_AWAKE
&& isItBedTimeYetLocked(id)) {
if (isAttentiveTimeoutExpired(id, time)) {
// ... 不考虑 attentive timeout，大部分项目不支持 ...
} else if (shouldNapAtBedTimeLocked()) {
// ... 如果开启了屏保，屏幕超时也会进入屏保 ...
} else {
// 更新 wakefulness 为 WAKEFULNESS_DOZING
changed = sleepDisplayGroupNoUpdateLocked(id, time,
PowerManager.GO_TO_SLEEP_REASON_TIMEOUT, 0, Process.SYSTEM_UID);
}
}
}
}
return changed;
}
private boolean isItBedTimeYetLocked(int groupId) {
if (!mBootCompleted) {
return false;
}
long now = mClock.uptimeMillis();
// 不考虑 attentive timeout，大部分项目不支持
if (isAttentiveTimeoutExpired(groupId, now)) {
return !isBeingKeptFromInattentiveSleepLocked(groupId);
} else {
return !isBeingKeptAwakeLocked(groupId);
}
}
private boolean isBeingKeptAwakeLocked(int groupId) {
return mStayOn // 开发者模式中是否打开"充电常亮"功能
|| mProximityPositive // 是否距离传感器保持亮屏
|| (mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId)
& WAKE_LOCK_STAY_AWAKE) != 0 // 是否有唤醒锁保持亮屏
|| (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId) & (
USER_ACTIVITY_SCREEN_BRIGHT | USER_ACTIVITY_SCREEN_DIM)) != 0 // 是否有亮屏的用户行为
|| mScreenBrightnessBoostInProgress; // 屏幕是否在亮度增强的过程中
}
现在要进入灭屏，只要没有因素保持屏幕长亮，那么就会更新 wakefulness 为 WAKEFULNESS_DOZING。
现在设备进入了打盹状态，打盹状态的流程不就是 PowerManagerService之手动灭屏 分析过了吗？ 如果设备进入打盹状态，并且能成功启动 doze dream，就会真正进入打盹状态，否则进入休眠状态。无论是设备进入打盹状态，还是休眠状态，屏幕最终会灭。
自动灭屏小结
自动灭屏的原理就是利用计算出的超时时间，发送一个定时消息来更新用户行为，必要时更新 wakefulness，也就是更新系统状态，从而改变请求的策略，最终改变了屏幕的状态(亮、灭、暗，等等)。
延长亮屏时间
现在我们讨论一个与自动灭屏有关的话题，那就是延长亮屏时间
private void updateUserActivitySummaryLocked(long now, int dirty) {
// ...
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
// 1. 自动灭屏前，用户触摸TP，会导致用户行为时间更新，从而延长亮屏时间
if (lastUserActivityTime >= mLastWakeTime) {
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
groupNextTimeout = lastUserActivityTime + screenOffTimeout;
if (now < groupNextTimeout) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
// 2. 如果有更新用户行为时带有 PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS，那么也会延长亮屏
if (groupUserActivitySummary == 0
&& lastUserActivityTimeNoChangeLights >= mLastWakeTime) {
// 根据 lastUserActivityTimeNoChangeLights 时间点重新计算灭屏时间
groupNextTimeout = lastUserActivityTimeNoChangeLights + screenOffTimeout;
if (now < groupNextTimeout) {
final DisplayPowerRequest displayPowerRequest =
mDisplayGroupPowerStateMapper.getPowerRequestLocked(groupId);
if (displayPowerRequest.policy == DisplayPowerRequest.POLICY_BRIGHT
|| displayPowerRequest.policy == DisplayPowerRequest.POLICY_VR) {
// 理论上讲，屏幕超时，屏幕会先变暗，然而这里处理的为何是亮屏的请求策略
// 这是因为，假如没有暗屏的时间呢？
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else if (displayPowerRequest.policy == DisplayPowerRequest.POLICY_DIM) {
groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
}
mDisplayGroupPowerStateMapper.setUserActivitySummaryLocked(groupId,
groupUserActivitySummary);
}
// ...
if (hasUserActivitySummary && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
}
可以看到，有两种情况可以延长亮屏的时间
- 屏幕处于亮/暗时，如果用户触摸TP，那么会更新更新用户行为时间，从而导致延长亮屏的时间。特别地，如果屏幕处于暗屏状态，那么点击触摸屏，会导致屏幕变亮。
- 如果有更新用户行为时带有 PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS，那么也会延长亮屏。
本文分析用户触摸TP导致的延长亮屏过程，另外一个请读者自行分析。
当用户触摸TP时，底层Input系统会通过JNI调用 PowerManagerService#userActivityFromNative()
// frameworks/base/services/core/jni/com_android_server_input_InputManagerService.cpp
void NativeInputManager::pokeUserActivity(nsecs_t eventTime, int32_t eventType) {
android_server_PowerManagerService_userActivity(eventTime, eventType);
}
// frameworks/base/services/core/jni/com_android_server_power_PowerManagerService.cpp
void android_server_PowerManagerService_userActivity(nsecs_t eventTime, int32_t eventType) {
if (gPowerManagerServiceObj) {
// 调用 Java 层的 PowerManagerService#userActivityFromNative()
env->CallVoidMethod(gPowerManagerServiceObj,
gPowerManagerServiceClassInfo.userActivityFromNative,
nanoseconds_to_milliseconds(eventTime), eventType, 0);
}
}
// PowerManagerService.java
private void userActivityFromNative(long eventTime, int event, int displayId, int flags) {
userActivityInternal(displayId, eventTime, event, flags, Process.SYSTEM_UID);
}
private void userActivityInternal(int displayId, long eventTime, int event, int flags,
int uid) {
synchronized (mLock) {
// ...
// 更新用户活动时间
if (userActivityNoUpdateLocked(groupId, eventTime, event, flags, uid)) {
// 更新电源状态
updatePowerStateLocked();
}
}
}
原来用户触摸TP，会更新用户行为的时间，那么用户行为也会发生改变
private void updateUserActivitySummaryLocked(long now, int dirty) {
// ...
// 先移除更新用户行为的定时消息
mHandler.removeMessages(MSG_USER_ACTIVITY_TIMEOUT);
// ...
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
// 用户触摸TP，更新了用户行为时间 lastUserActivityTime，因此这里重新计算超时时间
// 也就是说，延长了亮屏的时间
if (lastUserActivityTime >= mLastWakeTime) {
// 重新计算暗屏的超时时间
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) {
// 用户行为是亮屏
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
// ...
}
}
}
// ...
// 再次发送定时消息，更新用户行为
if (hasUserActivitySummary && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
}
由于用户行为时间的更新，导致重新计算了暗屏的超时时间，并且用户行为会更新为 USER_ACTIVITY_SCREEN_BRIGHT。
用户行为的更新，也导致了请求策略的更新，如下
int getDesiredScreenPolicyLocked(int groupId) {
final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
final int wakeLockSummary = mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId);
if (wakefulness == WAKEFULNESS_ASLEEP || sQuiescent) {
// ...
} else if (wakefulness == WAKEFULNESS_DOZING) {
// ...
}
if (mIsVrModeEnabled) {
// ...
}
if ((wakeLockSummary & WAKE_LOCK_SCREEN_BRIGHT) != 0
|| !mBootCompleted
|| (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId)
& USER_ACTIVITY_SCREEN_BRIGHT) != 0
|| mScreenBrightnessBoostInProgress) {
return DisplayPowerRequest.POLICY_BRIGHT;
}
// ...
}
可以看到，如果屏幕处于亮/暗状态，用户触摸TP，请求策略更新为 DisplayPowerRequest.POLICY_BRIGHT， 最终导致屏幕为亮屏状态。
另外，重新计算出的暗屏超时时间，会被用来发送定时消息来更新用户行为，因此就相当于重置了屏幕超时时间。
因此，触摸TP导致屏幕处于亮屏状态，并且重置了屏幕超时时间，那么就相当于延长了亮屏的时间。
结束
如果明白了亮屏与灭屏的过程，自动灭屏的原理就没有那么复杂，如果读者在阅读本文时，发现很多东西讲的很简单，那是因为前面的文章已经分析过，所以读者务必仔细阅读前面两篇文章。
以目前的三篇文章为根基，下一篇文章，我们将讨论 PowerManagerService 的最后一个话题，唤醒锁。
以上就是PowerManagerService之自动灭屏流程解析的详细内容，更多关于PowerManagerService 自动灭屏的资料请关注编程网其它相关文章！
