亮屏的方式有很多，其中最常用的是 Power 键亮屏，这个流程比较简单，本文希望通过分析这个流程，从而理清操作屏幕的能用流程，为后面的文章打下基础。
本文以 Power 键亮屏为例进行分析，它会调用 PowerManagerService#wakeUp()
// PowerManagerService.java
@Override // Binder call
public void wakeUp(long eventTime, @WakeReason int reason, String details,
String opPackageName) {
// ...
try {
// 只能唤醒 default display group 下的显示屏
wakeDisplayGroup(Display.DEFAULT_DISPLAY_GROUP, eventTime, reason, details, uid,
opPackageName, uid);
} finally {
Binder.restoreCallingIdentity(ident);
}
}
private void wakeDisplayGroup(int groupId, long eventTime, @WakeReason int reason,
String details, int uid, String opPackageName, int opUid) {
synchronized (mLock) {
// 1. 更新 wakefulness 为 WAKEFULNESS_AWAKE
// 包括更新 PowerManagerService 和 DisplayGroupPowerStateMapper 的 wakefulness
if (wakeDisplayGroupNoUpdateLocked(groupId, eventTime, reason, details, uid,
opPackageName, opUid)) {
// 2. 更新电源状态
updatePowerStateLocked();
}
}
}
注意，PowerManagerService#wakeUp() 只能操作默认分组下的屏幕。
Android 不知何时起，对多屏幕添加了一个分组功能，手机通常只有一个屏幕，它属于默认分组。
亮屏的过程有两步
private boolean wakeDisplayGroupNoUpdateLocked(int groupId, long eventTime,
@WakeReason int reason, String details, int uid, String opPackageName, int opUid) {
// ...
try {
// ...
// 设置 wakefulness 为 WAKEFULNESS_AWAKE
setWakefulnessLocked(groupId, WAKEFULNESS_AWAKE, eventTime, uid, reason, opUid,
opPackageName, details);
// 更新分组显示屏的信息
mDisplayGroupPowerStateMapper.setLastPowerOnTimeLocked(groupId, eventTime);
mDisplayGroupPowerStateMapper.setPoweringOnLocked(groupId, true);
}
return true;
}
void setWakefulnessLocked(int groupId, int wakefulness, long eventTime, int uid, int reason,
int opUid, String opPackageName, String details) {
// 1. 更新 DisplayGroupPowerStateMapper 的 wakefulness
if (mDisplayGroupPowerStateMapper.setWakefulnessLocked(groupId, wakefulness)) {
// display group wakefulness 改变了
mDirty |= DIRTY_DISPLAY_GROUP_WAKEFULNESS;
// 2. 更新 PMS 的 wakefulness
// 注意第一个参数取所有 display group 的最大的 wakefulness，优先级如下
// PowerManagerInternal#WAKEFULNESS_AWAKE
// PowerManagerInternal#WAKEFULNESS_DREAMING
// PowerManagerInternal#WAKEFULNESS_DOZING
// PowerManagerInternal#WAKEFULNESS_ASLEEP
// TODO: 为何 PMS 的 wakefulness 要设置为所有 display group 的最大的 wakefulness ?
setGlobalWakefulnessLocked(mDisplayGroupPowerStateMapper.getGlobalWakefulnessLocked(),
eventTime, reason, uid, opUid, opPackageName, details);
if (wakefulness == WAKEFULNESS_AWAKE) {
// Kick user activity to prevent newly awake group from timing out instantly.
// 3. 保存用户行为的时间
userActivityNoUpdateLocked(
groupId, eventTime, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, uid);
}
}
}
更新 wakefulness 为 WAKEFULNESS_AWAKE 过程如下
// PowerManagerService.java
private void setGlobalWakefulnessLocked(int wakefulness, long eventTime, int reason, int uid,
int opUid, String opPackageName, String details) {
if (getWakefulnessLocked() == wakefulness) {
return;
}
// Phase 1: Handle pre-wakefulness change bookkeeping.
final String traceMethodName;
switch (wakefulness) {
// ...
case WAKEFULNESS_AWAKE:
// 保存唤醒设备的时间
// 这个时间，后面在更新用户行为的时候会用到
mLastWakeTime = eventTime;
mLastWakeReason = reason;
break;
// ...
}
try {
// Phase 2: Handle wakefulness change and bookkeeping.
// Under lock, invalidate before set ensures caches won't return stale values.
mInjector.invalidateIsInteractiveCaches();
// 更新 PMS 的 wakefulness 相关变量
mWakefulnessRaw = wakefulness;
mWakefulnessChanging = true;
// mDirty 设置 DIRTY_WAKEFULNESS，表示 PMS 的 wakefulness 改变了
mDirty |= DIRTY_WAKEFULNESS;
mDozeStartInProgress &= (getWakefulnessLocked() == WAKEFULNESS_DOZING);
// 通知其它组件，wakefulness改变 或者 交互状态改变
if (mNotifier != null) {
mNotifier.onWakefulnessChangeStarted(wakefulness, reason, eventTime);
}
mAttentionDetector.onWakefulnessChangeStarted(wakefulness);
// Phase 3: Handle post-wakefulness change bookkeeping.
switch (wakefulness) {
case WAKEFULNESS_AWAKE:
// 记录并检测是否有权限
mNotifier.onWakeUp(reason, details, uid, opPackageName, opUid);
if (sQuiescent) {
mDirty |= DIRTY_QUIESCENT;
}
break;
// ...
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_POWER);
}
}
根据英文注释，更新 PMS 的 wakefulness 过程分为三个阶段，最主要的是在第二个阶段，更新 wakefulness 相关变量，然后 Notifier 通知其它组件并发送亮屏通知，过程如下，大家看一下就行，这不是重点。
// Notifier.java
public void onWakefulnessChangeStarted(final int wakefulness, int reason, long eventTime) {
// 判断新的 wakefulness 是否是交互状态
// WAKEFULNESS_AWAKE 是可交互状态
final boolean interactive = PowerManagerInternal.isInteractive(wakefulness);
// 1. 通知 AMS wakefulness 改变了
mHandler.post(new Runnable() {
@Override
public void run() {
mActivityManagerInternal.onWakefulnessChanged(wakefulness);
}
});
// 2. 处理交互状态改变
// Handle any early interactive state changes.
// Finish pending incomplete ones from a previous cycle.
// 处理早期交互状态改变
if (mInteractive != interactive) {
// Finish up late behaviors if needed.
// mInteractiveChanging 为 true，表示上一次的处理流程还没有执行完
// 这里会先执行上一次的流程
if (mInteractiveChanging) {
handleLateInteractiveChange();
}
// 2.1 更新系统组件的交互状态
// Start input as soon as we start waking up or going to sleep.
mInputManagerInternal.setInteractive(interactive);
mInputMethodManagerInternal.setInteractive(interactive);
// ...
// Handle early behaviors.
// 2.2 更新关于交互状态的变量
mInteractive = interactive;
mInteractiveChangeReason = reason;
mInteractiveChangeStartTime = eventTime;
// 交互状态正在改变
mInteractiveChanging = true;
// 2.3 处理早期的交互状态改变任务
handleEarlyInteractiveChange();
}
}
private void handleEarlyInteractiveChange() {
synchronized (mLock) {
if (mInteractive) {
// 通知 PhoneWindowManager，PhoneWindowManager再通知 SystemUI keyguard
mHandler.post(() -> mPolicy.startedWakingUp(mInteractiveChangeReason));
// 发送亮屏广播
mPendingInteractiveState = INTERACTIVE_STATE_AWAKE;
mPendingWakeUpBroadcast = true;
updatePendingBroadcastLocked();
} else {
// ...
}
}
}
// PowerManagerService.java
private boolean userActivityNoUpdateLocked(int groupId, long eventTime, int event, int flags,
int uid) {
if (eventTime < mLastSleepTime || eventTime < mLastWakeTime || !mSystemReady) {
return false;
}
Trace.traceBegin(Trace.TRACE_TAG_POWER, "userActivity");
try {
if (eventTime > mLastInteractivePowerHintTime) {
setPowerBoostInternal(Boost.INTERACTION, 0);
mLastInteractivePowerHintTime = eventTime;
}
// 1. 通知系统组件，有用户行为发生
mNotifier.onUserActivity(event, uid);
mAttentionDetector.onUserActivity(eventTime, event);
if (mUserInactiveOverrideFromWindowManager) {
mUserInactiveOverrideFromWindowManager = false;
mOverriddenTimeout = -1;
}
final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
if (wakefulness == WAKEFULNESS_ASLEEP
|| wakefulness == WAKEFULNESS_DOZING
|| (flags & PowerManager.USER_ACTIVITY_FLAG_INDIRECT) != 0) {
return false;
}
maybeUpdateForegroundProfileLastActivityLocked(eventTime);
if ((flags & PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS) != 0) {
// 这里处理延长亮屏的时间的逻辑 ...
} else {
if (eventTime > mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(
groupId)) {
// 2. 保存用户活动时间
mDisplayGroupPowerStateMapper.setLastUserActivityTimeLocked(groupId, eventTime);
// 3. mDirty 设置 DIRTY_USER_ACTIVITY 标志位，
// 表示用户活动有更新
mDirty |= DIRTY_USER_ACTIVITY;
if (event == PowerManager.USER_ACTIVITY_EVENT_BUTTON) {
mDirty |= DIRTY_QUIESCENT;
}
return true;
}
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_POWER);
}
return false;
}
PMS 更新用户行为的过程
简单看下第一步的过程，如下
private void sendUserActivity(int event) {
synchronized (mLock) {
if (!mUserActivityPending) {
return;
}
mUserActivityPending = false;
}
// 这里暂时不知道做了什么
TelephonyManager tm = mContext.getSystemService(TelephonyManager.class);
tm.notifyUserActivity();
// PhoneWindowManger 会通知 SystemUI
mPolicy.userActivity();
// 如果 FaceDownDetector 正在执行翻转灭屏任务，此时有用户行为，取消这个任务
mFaceDownDetector.userActivity(event);
}
通过上面的分析，我们应该看到一个本质，更新 wakefulness 流程大致如下
// PowerManagerService.java
private void updatePowerStateLocked() {
if (!mSystemReady || mDirty == 0) {
return;
}
// 注意这里的技术，线程可以判断是否获取了某个锁
if (!Thread.holdsLock(mLock)) {
Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");
}
Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");
try {
// Phase 0: Basic state updates.
// 省电模式功能
updateIsPoweredLocked(mDirty);
// 设置中"充电常亮功能"
updateStayOnLocked(mDirty);
// 亮度增加功能
updateScreenBrightnessBoostLocked(mDirty);
// Phase 1: Update wakefulness.
// Loop because the wake lock and user activity computations are influenced
// by changes in wakefulness.
final long now = mClock.uptimeMillis();
int dirtyPhase2 = 0;
for (;;) {
int dirtyPhase1 = mDirty;
dirtyPhase2 |= dirtyPhase1;
mDirty = 0;
// 把所有的唤醒锁归纳到 mWakeLockSummary
updateWakeLockSummaryLocked(dirtyPhase1);
// 1. 更新用户行为
updateUserActivitySummaryLocked(now, dirtyPhase1);
updateAttentiveStateLocked(now, dirtyPhase1);
// 决定是否进入休眠/dream/doze状态
// 如果进入某一种状态，会更新 wakefulness，因此这里要通过循环再来更新上面的东西
if (!updateWakefulnessLocked(dirtyPhase1)) {
break;
}
}
// Phase 2: Lock profiles that became inactive/not kept awake.
updateProfilesLocked(now);
// Phase 3: Update display power state.
// 2. 更新显示屏的电源状态
final boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);
// Phase 4: Update dream state (depends on display ready signal).
updateDreamLocked(dirtyPhase2, displayBecameReady);
// Phase 5: Send notifications, if needed.
finishWakefulnessChangeIfNeededLocked();
// Phase 6: Update suspend blocker.
// Because we might release the last suspend blocker here, we need to make sure
// we finished everything else first!
updateSuspendBlockerLocked();
} finally {
Trace.traceEnd(Trace.TRACE_TAG_POWER);
}
}
PowerManagerService 的所有功能都集中在这个函数中，但是与亮屏相关的主要有两步
// PowerManagerService.java
private void updateUserActivitySummaryLocked(long now, int dirty) {
// Update the status of the user activity timeout timer.
if ((dirty & (DIRTY_DISPLAY_GROUP_WAKEFULNESS | DIRTY_WAKE_LOCKS
| DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS | DIRTY_SETTINGS)) == 0) {
return;
}
mHandler.removeMessages(MSG_USER_ACTIVITY_TIMEOUT);
// 默认为 -1
final long attentiveTimeout = getAttentiveTimeoutLocked();
// 休眠超时时间，默认为 -1
final long sleepTimeout = getSleepTimeoutLocked(attentiveTimeout);
// 屏幕超时时间
long screenOffTimeout = getScreenOffTimeoutLocked(sleepTimeout,
attentiveTimeout);
// dim duration = 20 % screen off timeout
final long screenDimDuration = getScreenDimDurationLocked(screenOffTimeout);
screenOffTimeout =
getScreenOffTimeoutWithFaceDownLocked(screenOffTimeout, screenDimDuration);
final boolean userInactiveOverride = mUserInactiveOverrideFromWindowManager;
long nextTimeout = -1;
boolean hasUserActivitySummary = false;
// 遍历 display group id
for (int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
int groupUserActivitySummary = 0;
long groupNextTimeout = 0;
// 注意，休眠状态是无法决定用户行为的
if (mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId) != WAKEFULNESS_ASLEEP) {
final long lastUserActivityTime =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeLocked(groupId);
final long lastUserActivityTimeNoChangeLights =
mDisplayGroupPowerStateMapper.getLastUserActivityTimeNoChangeLightsLocked(
groupId);
// 1. 获取用户行为与超时时间
// 上一次用户行为的时间 >= 上一次唤醒屏幕的时间
if (lastUserActivityTime >= mLastWakeTime) {
groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
if (now < groupNextTimeout) { // 没有到 dim 时间
groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
} else {
groupNextTimeout = lastUserActivityTime + screenOffTimeout;
if (now < groupNextTimeout) { // 处于 dim 时间段
groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
}
}
}
// 超时了，但是由于释放了某一个锁，需要延长亮屏时间
if (groupUserActivitySummary == 0
&& lastUserActivityTimeNoChangeLights >= mLastWakeTime) {
// ...
}
// 一般的超时情况，
if (groupUserActivitySummary == 0) {
// ...
}
// PhoneWindowManager 处理 KeyEvent.KEYCODE_SOFT_SLEEP 时，userInactiveOverride 为 true
// KeyEvent.KEYCODE_SOFT_SLEEP 这个软件的休眠按键 ？
if (groupUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM
&& userInactiveOverride) {
// ...
}
// 用户行为是点亮屏幕，并且WakeLock没有保持屏幕常亮，用AttentionDetector再次计算屏幕超时时间
if ((groupUserActivitySummary & USER_ACTIVITY_SCREEN_BRIGHT) != 0
&& (mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId)
& WAKE_LOCK_STAY_AWAKE) == 0) {
// ...
}
hasUserActivitySummary |= groupUserActivitySummary != 0;
if (nextTimeout == -1) {
nextTimeout = groupNextTimeout;
} else if (groupNextTimeout != -1) {
// 这里表示 nextTimeout != -1 的情况，也说明有多个 display group 的情况
// 从这里可以看出，多个 display group 的超时时间是相同的
nextTimeout = Math.min(nextTimeout, groupNextTimeout);
}
}
// 2. DisplayGroupPowerStateMapper 保存用户行为
mDisplayGroupPowerStateMapper.setUserActivitySummaryLocked(groupId,
groupUserActivitySummary);
}
} // 遍历 display group id 结束
final long nextProfileTimeout = getNextProfileTimeoutLocked(now);
if (nextProfileTimeout > 0) {
nextTimeout = Math.min(nextTimeout, nextProfileTimeout);
}
// 3. 定时更新电源状态
// 这一步决定自动灭屏
if (hasUserActivitySummary && nextTimeout >= 0) {
scheduleUserInactivityTimeout(nextTimeout);
}
}
这个函数不单单是用于更新用户行为，还更新了屏幕超时时间，并且以这个时间来定时更新电源状态，以实现自动灭屏的功能。
更新用户行为在第1步，前面分析更新 wakefulness 时，PMS 保存了唤醒的时间 mLastWakeTime，以及 DisplayGroupPowerStateMapper 保存了用户行为时间。因此，对于从灭屏状态到亮屏状态这一过程来说，用户行为的值现在是 USER_ACTIVITY_SCREEN_BRIGHT，表示用户行为是亮屏。
// PowerManagerService.java
private boolean updateDisplayPowerStateLocked(int dirty) {
final boolean oldDisplayReady = mDisplayGroupPowerStateMapper.areAllDisplaysReadyLocked();
if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_WAKEFULNESS
| DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED | DIRTY_BOOT_COMPLETED
| DIRTY_SETTINGS | DIRTY_SCREEN_BRIGHTNESS_BOOST | DIRTY_VR_MODE_CHANGED |
DIRTY_QUIESCENT | DIRTY_DISPLAY_GROUP_WAKEFULNESS)) != 0) {
if ((dirty & DIRTY_QUIESCENT) != 0) {
// ...
}
// 遍历 display group
for (final int groupId : mDisplayGroupPowerStateMapper.getDisplayGroupIdsLocked()) {
// 1. 获取 display group 的请求
final DisplayPowerRequest displayPowerRequest =
mDisplayGroupPowerStateMapper.getPowerRequestLocked(groupId);
// 2. 更新请求的各种参数
// 更新请求的策略参数，所谓的策略，就是亮屏，还是灭屏，或者使屏幕变暗，等等
displayPowerRequest.policy = getDesiredScreenPolicyLocked(groupId);
// ...省略更新其它请求参数的过程...
// 3. 向 DisplayManagerService 发起请求
// 如果此次请求与上一次的请求不同，那么这个请求的处理是一个异步处理过程，此时返回 false。
// 否则，不用处理，直接返回 true。
final boolean ready = mDisplayManagerInternal.requestPowerState(groupId,
displayPowerRequest, mRequestWaitForNegativeProximity);
// 更新 DisplayGroupPowerStateMapper 的 ready 状态
final boolean displayReadyStateChanged =
mDisplayGroupPowerStateMapper.setDisplayGroupReadyLocked(groupId, ready);
// 如果异步请求处理完毕，DMS 会回调通知 PMS，PMS 再更新状态走到这里
// 如果点亮屏幕时间过长，那么用log记录下来
final boolean poweringOn =
mDisplayGroupPowerStateMapper.isPoweringOnLocked(groupId);
if (ready && displayReadyStateChanged && poweringOn
&& mDisplayGroupPowerStateMapper.getWakefulnessLocked(
groupId) == WAKEFULNESS_AWAKE) {
mDisplayGroupPowerStateMapper.setPoweringOnLocked(groupId, false);
Trace.asyncTraceEnd(Trace.TRACE_TAG_POWER, TRACE_SCREEN_ON, groupId);
final int latencyMs = (int) (mClock.uptimeMillis()
- mDisplayGroupPowerStateMapper.getLastPowerOnTimeLocked(groupId));
if (latencyMs >= SCREEN_ON_LATENCY_WARNING_MS) {
Slog.w(TAG, "Screen on took " + latencyMs + " ms");
}
}
}
mRequestWaitForNegativeProximity = false;
}
// 返回值表示是否从非ready状态变为ready状态
return mDisplayGroupPowerStateMapper.areAllDisplaysReadyLocked() && !oldDisplayReady;
}
更新屏幕电源状态的很清晰，如下
我们来看下如何更新请求的策略
// PowerManagerService.java
int getDesiredScreenPolicyLocked(int groupId) {
final int wakefulness = mDisplayGroupPowerStateMapper.getWakefulnessLocked(groupId);
final int wakeLockSummary = mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId);
if (wakefulness == WAKEFULNESS_ASLEEP || sQuiescent) {
return DisplayPowerRequest.POLICY_OFF;
} else if (wakefulness == WAKEFULNESS_DOZING) {
// ...
}
if (mIsVrModeEnabled) {
return DisplayPowerRequest.POLICY_VR;
}
// 由于此时的 UserActivity 为 USER_ACTIVITY_SCREEN_BRIGHT，因此策略为 DisplayPowerRequest.POLICY_BRIGHT
if ((wakeLockSummary & WAKE_LOCK_SCREEN_BRIGHT) != 0
|| !mBootCompleted
|| (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId)
& USER_ACTIVITY_SCREEN_BRIGHT) != 0
|| mScreenBrightnessBoostInProgress) {
return DisplayPowerRequest.POLICY_BRIGHT;
}
return DisplayPowerRequest.POLICY_DIM;
}
我们刚才分析的用户行为是 USER_ACTIVITY_SCREEN_BRIGHT，因此策略最终为 DisplayPowerRequest.POLICY_BRIGHT。当向 DisplayManagerService 发起请求时，最终会导致屏幕点亮。
前面我们刚提到过，处理屏幕请求的过程可能是一个异步，也可能是一个同步。如果从灭屏到亮屏，这个过程一定是一个异步的，那么 PowerManagerService 是如何得知 DisplayManagerService 已经处理完成了呢？ 其实 PowerManagerService 向 DisplayManagerService 注册过回调
// PowerManagerService.java
public void systemReady(IAppOpsService appOps) {
synchronized (mLock) {
mDisplayManagerInternal.initPowerManagement(
mDisplayPowerCallbacks, mHandler, sensorManager);
}
}
private final DisplayManagerInternal.DisplayPowerCallbacks mDisplayPowerCallbacks =
new DisplayManagerInternal.DisplayPowerCallbacks() {
@Override
public void onStateChanged() {
synchronized (mLock) {
// 表示屏幕状态更新了
mDirty |= DIRTY_ACTUAL_DISPLAY_POWER_STATE_UPDATED;
updatePowerStateLocked();
}
}
}
当 PowerManagerService 通过回调得知 DisplayManagerService 已经处理完屏幕请求，于是再次更新电源状态。
此时，updateDisplayPowerStateLocked() 再向 DisplayManagerService 发起请求，由于与上一次请求相同，因此 DisplayManagerService 不做处理，返回的 ready 状态为 true。
更新电源状态剩下的过程，就是收尾，我们大致看下
// PowerManagerService.java
private void finishWakefulnessChangeIfNeededLocked() {
// 注意，其中一个条件就是所有 display group 要 ready
if (mWakefulnessChanging && mDisplayGroupPowerStateMapper.areAllDisplaysReadyLocked()) {
// ...
// 显示屏 ready 了， PMS 的 wakefulness 改变的工作才算处理完
mWakefulnessChanging = false;
// Notier 通知 wakefulness 的改变已经完成
mNotifier.onWakefulnessChangeFinished();
}
}
// Notifier.java
public void onWakefulnessChangeFinished() {
if (mInteractiveChanging) {
mInteractiveChanging = false;
// 处理交互状态的后期任务
handleLateInteractiveChange();
}
}
private void handleLateInteractiveChange() {
synchronized (mLock) {
final int interactiveChangeLatency =
(int) (SystemClock.uptimeMillis() - mInteractiveChangeStartTime);
if (mInteractive) {
// Finished waking up...
mHandler.post(() -> {
// 通知 PhoneWindowManager 完成设备唤醒工作
mPolicy.finishedWakingUp(mInteractiveChangeReason);
});
} else {
// ...
}
}
}
我们分析的是从灭屏到亮屏的过程，但是我们应该看到一个本质的问题，它其实就是向 DislayManagerService 发起请求，来更新屏幕状态(例如 亮屏，灭屏)。
请求的策略最终决定了屏幕在状态，但是影响请求策略的因素有很多，例如系统状态(指的是PMS的wakefulness)，用户行为，唤醒锁，等等。我们将在后面的文章中看到更多决定请求策略的情况。
本文虽然分析的是从灭屏到亮屏的流程，但是我们要看到一个本质的过程，其实只有两步
