PowerManagerService之自動(dòng)滅屏流程解析

更新時(shí)間：2022年10月28日 08:52:01 作者：大胃粥

這篇文章主要為大家介紹了PowerManagerService之自動(dòng)滅屏流程解析，有需要的朋友可以借鑒參考下，希望能夠有所幫助，祝大家多多進(jìn)步，早日升職加薪

前言

PowerManagerService之亮屏流程分析歸納了亮屏/滅屏的通用流程，PowerManagerService之手動(dòng)滅屏對(duì)手動(dòng)滅屏流程進(jìn)行了整體的分析。本文以前兩篇文章為基礎(chǔ)，來分析自動(dòng)滅屏，請(qǐng)讀者務(wù)必仔細(xì)閱讀前兩篇文章。

自動(dòng)滅屏

要想分析自動(dòng)滅屏，需得回顧下 PowerManagerService之亮屏流程分析的亮屏邏輯的一些細(xì)節(jié)。

在亮屏的時(shí)候，會(huì)保存亮屏的時(shí)間，以及用戶行為的時(shí)間，這兩個(gè)時(shí)間用于決定用戶行為，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 表示上次亮屏的時(shí)間
            // lastUserActivityTime 表示上次用戶行為的時(shí)間
            if (lastUserActivityTime >= mLastWakeTime) {
                // 計(jì)算使屏幕變暗的超時(shí)時(shí)間
                groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
                if (now < groupNextTimeout) {
                    groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
                } else {
                    // ...
                }
            }
            // ...
    }
    // ...
}

此時(shí)得到的用戶行為是 USER_ACTIVITY_SCREEN_BRIGHT，表明用戶行為是要點(diǎn)亮屏幕。

之后會(huì)向 DisplayManagerService 發(fā)起請(qǐng)求，而最終決定屏幕狀態(tài)(亮、滅、暗，等等)的請(qǐng)求策略，它的更新過程如下

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;
    }
    // ...
}

由于用戶行為是 USER_ACTIVITY_SCREEN_BRIGHT，因此策略為 DisplayPowerRequest.POLICY_BRIGHT，它最終導(dǎo)致屏幕變亮。

那么亮屏后，是如何自動(dòng)滅屏呢？

// 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) {
                // 使屏幕變暗的超時(shí)時(shí)間
                groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
                if (now < groupNextTimeout) {
                    groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
                } else {
                    // ...
                }
            }
            // ...
    }
    // 使用屏幕變暗的超時(shí)時(shí)間，發(fā)送一個(gè)定時(shí)消息來更新用戶行為
    if (hasUserActivitySummary && nextTimeout >= 0) {
        scheduleUserInactivityTimeout(nextTimeout);
    }
}
private void scheduleUserInactivityTimeout(long timeMs) {
    final Message msg = mHandler.obtainMessage(MSG_USER_ACTIVITY_TIMEOUT);
    msg.setAsynchronous(true);
    // 利用超時(shí)時(shí)間，發(fā)送一個(gè)定時(shí)消息，更新用戶行為
    // 最終調(diào)用 handleUserActivityTimeout
    mHandler.sendMessageAtTime(msg, timeMs);
}
private void handleUserActivityTimeout() { // runs on handler thread
    synchronized (mLock) {
        // 標(biāo)記用戶行為需要更新
        mDirty |= DIRTY_USER_ACTIVITY;
        // 重新更新電源狀態(tài)，其實(shí)就是為了更新用戶行為
        updatePowerStateLocked();
    }
}

從上面的代碼邏輯可以看出，當(dāng) Power 鍵亮屏后，會(huì)計(jì)算出使屏幕變暗的超時(shí)時(shí)間，然后利用這個(gè)超時(shí)時(shí)間，發(fā)送了一個(gè)定時(shí)消息，當(dāng)屏幕變暗的超時(shí)時(shí)間到了，就會(huì)再次更新用戶行為，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 {
                    // 計(jì)算滅屏的超時(shí)時(shí)間
                    groupNextTimeout = lastUserActivityTime + screenOffTimeout;
                    if (now < groupNextTimeout) { // 進(jìn)入 DIM 時(shí)間段
                        // 更新用戶行為
                        groupUserActivitySummary = USER_ACTIVITY_SCREEN_DIM;
                    }
                }
            }
            // ...
    }
    // ...
    // 使用滅屏的超時(shí)時(shí)間，發(fā)送一個(gè)定時(shí)消息來更新用戶行為
    if (hasUserActivitySummary && nextTimeout >= 0) {
        scheduleUserInactivityTimeout(nextTimeout);
    }    
}

此次用戶行為的更新，計(jì)算的是滅屏的超時(shí)時(shí)間，然后用戶行為更新為 USER_ACTIVITY_SCREEN_DIM，表示用戶行為要使屏幕變暗。最后利用滅屏的超時(shí)時(shí)間，發(fā)送了一個(gè)定時(shí)消息來再次更新用戶行為。

現(xiàn)在用戶行為是使屏幕變暗，再看看請(qǐng)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;
}

請(qǐng)求策略更新為 DisplayPowerRequest.POLICY_DIM，最終它會(huì)使屏幕變暗。

當(dāng)滅屏的超時(shí)時(shí)間到了，我們看下再次更新用戶行為時(shí)，會(huì)發(fā)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;
                    }
                }
            }
            // 滅屏超時(shí)前，帶有 PowerManager.ON_AFTER_RELEASE 這個(gè)flag的喚醒鎖釋放，延長屏幕的亮/暗的時(shí)間
            if (groupUserActivitySummary == 0
                    && lastUserActivityTimeNoChangeLights >= mLastWakeTime) {
                // ...
            }
            // 滅屏超時(shí)，允許進(jìn)入屏保
            if (groupUserActivitySummary == 0) {
                // ...
            }
            // 按鍵 KeyEvent.KEYCODE_SOFT_SLEEP 進(jìn)入屏保
            if (groupUserActivitySummary != USER_ACTIVITY_SCREEN_DREAM
                    && userInactiveOverride) {
                // ...
            }
            // 用 AttentionDetector 重新計(jì)算超時(shí)時(shí)間，目前不分析
            if ((groupUserActivitySummary & USER_ACTIVITY_SCREEN_BRIGHT) != 0
                    && (mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId)
                    & WAKE_LOCK_STAY_AWAKE) == 0) {
                // ...
            }
            // 確定是否有用戶行為
            hasUserActivitySummary |= groupUserActivitySummary != 0;
            // 保存超時(shí)時(shí)間
            if (nextTimeout == -1) {
                nextTimeout = groupNextTimeout;
            } else if (groupNextTimeout != -1) {
                nextTimeout = Math.min(nextTimeout, groupNextTimeout);
            }
        }
        // DisplayGroupPowerStateMapper 保存用戶行為
        mDisplayGroupPowerStateMapper.setUserActivitySummaryLocked(groupId,
                groupUserActivitySummary);
    }
    final long nextProfileTimeout = getNextProfileTimeoutLocked(now);
    if (nextProfileTimeout > 0) {
        nextTimeout = Math.min(nextTimeout, nextProfileTimeout);
    }
    // 利用超時(shí)時(shí)間，發(fā)送一個(gè)定時(shí)消息
    if (hasUserActivitySummary && nextTimeout >= 0) {
        scheduleUserInactivityTimeout(nextTimeout);
    }
}

可以看到滅屏超時(shí)時(shí)間到了時(shí)，有很多因素會(huì)再次影響用戶行為和超時(shí)時(shí)間，我們忽略這些因素，因此超時(shí)時(shí)間和用戶行為都為0。既然沒有了用戶行為和超時(shí)時(shí)間，那么自然不會(huì)發(fā)送定時(shí)消息來更新用戶行為了，因?yàn)轳R上就要滅屏的嘛，就沒必要去定時(shí)更新用戶行為了。

此時(shí)，我要提醒大家，從亮屏到自動(dòng)滅屏的過程中，此時(shí) wakefulness 還是 WAKEFULNESS_AWAKE，現(xiàn)在馬上要滅屏了，因此需要再次更新 wakefulness，這就是更新電源狀態(tài)過程中，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)) {
                    // ... 不考慮 attentive timeout，大部分項(xiàng)目不支持 ...
                } else if (shouldNapAtBedTimeLocked()) {
                    // ... 如果開啟了屏保，屏幕超時(shí)也會(huì)進(jìn)入屏保 ...
                } else {
                    // 更新 wakefulness 為 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();
    // 不考慮 attentive timeout，大部分項(xiàng)目不支持
    if (isAttentiveTimeoutExpired(groupId, now)) {
        return !isBeingKeptFromInattentiveSleepLocked(groupId);
    } else {
        return !isBeingKeptAwakeLocked(groupId);
    }
}
private boolean isBeingKeptAwakeLocked(int groupId) {
    return mStayOn // 開發(fā)者模式中是否打開"充電常亮"功能
            || mProximityPositive // 是否距離傳感器保持亮屏
            || (mDisplayGroupPowerStateMapper.getWakeLockSummaryLocked(groupId)
            & WAKE_LOCK_STAY_AWAKE) != 0 // 是否有喚醒鎖保持亮屏
            || (mDisplayGroupPowerStateMapper.getUserActivitySummaryLocked(groupId) & (
            USER_ACTIVITY_SCREEN_BRIGHT | USER_ACTIVITY_SCREEN_DIM)) != 0 // 是否有亮屏的用戶行為
            || mScreenBrightnessBoostInProgress; // 屏幕是否在亮度增強(qiáng)的過程中
}

現(xiàn)在要進(jìn)入滅屏，只要沒有因素保持屏幕長亮，那么就會(huì)更新 wakefulness 為 WAKEFULNESS_DOZING。

現(xiàn)在設(shè)備進(jìn)入了打盹狀態(tài)，打盹狀態(tài)的流程不就是 PowerManagerService之手動(dòng)滅屏分析過了嗎？如果設(shè)備進(jìn)入打盹狀態(tài)，并且能成功啟動(dòng) doze dream，就會(huì)真正進(jìn)入打盹狀態(tài)，否則進(jìn)入休眠狀態(tài)。無論是設(shè)備進(jìn)入打盹狀態(tài)，還是休眠狀態(tài)，屏幕最終會(huì)滅。

自動(dòng)滅屏小結(jié)

自動(dòng)滅屏的原理就是利用計(jì)算出的超時(shí)時(shí)間，發(fā)送一個(gè)定時(shí)消息來更新用戶行為，必要時(shí)更新 wakefulness，也就是更新系統(tǒng)狀態(tài)，從而改變請(qǐng)求的策略，最終改變了屏幕的狀態(tài)(亮、滅、暗，等等)。

延長亮屏?xí)r間

現(xiàn)在我們討論一個(gè)與自動(dòng)滅屏有關(guān)的話題，那就是延長亮屏?xí)r間

    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. 自動(dòng)滅屏前，用戶觸摸TP，會(huì)導(dǎo)致用戶行為時(shí)間更新，從而延長亮屏?xí)r間
                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. 如果有更新用戶行為時(shí)帶有  PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS，那么也會(huì)延長亮屏
                if (groupUserActivitySummary == 0
                        && lastUserActivityTimeNoChangeLights >= mLastWakeTime) {
                    // 根據(jù)  lastUserActivityTimeNoChangeLights 時(shí)間點(diǎn)重新計(jì)算滅屏?xí)r間
                    groupNextTimeout = lastUserActivityTimeNoChangeLights + screenOffTimeout;
                    if (now < groupNextTimeout) {
                        final DisplayPowerRequest displayPowerRequest =
                                mDisplayGroupPowerStateMapper.getPowerRequestLocked(groupId);
                        if (displayPowerRequest.policy == DisplayPowerRequest.POLICY_BRIGHT
                                || displayPowerRequest.policy == DisplayPowerRequest.POLICY_VR) {
                            // 理論上講，屏幕超時(shí)，屏幕會(huì)先變暗，然而這里處理的為何是亮屏的請(qǐng)求策略
                            // 這是因?yàn)?，假如沒有暗屏的時(shí)間呢？
                            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，有兩種情況可以延長亮屏的時(shí)間

屏幕處于亮/暗時(shí)，如果用戶觸摸TP，那么會(huì)更新更新用戶行為時(shí)間，從而導(dǎo)致延長亮屏的時(shí)間。特別地，如果屏幕處于暗屏狀態(tài)，那么點(diǎn)擊觸摸屏，會(huì)導(dǎo)致屏幕變亮。
如果有更新用戶行為時(shí)帶有 PowerManager.USER_ACTIVITY_FLAG_NO_CHANGE_LIGHTS，那么也會(huì)延長亮屏。

本文分析用戶觸摸TP導(dǎo)致的延長亮屏過程，另外一個(gè)請(qǐng)讀者自行分析。

當(dāng)用戶觸摸TP時(shí)，底層Input系統(tǒng)會(huì)通過JNI調(diào)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) {
        // 調(diào)用 Java 層的 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) {
        // ...
        // 更新用戶活動(dòng)時(shí)間
        if (userActivityNoUpdateLocked(groupId, eventTime, event, flags, uid)) {
            // 更新電源狀態(tài)
            updatePowerStateLocked();
        }
    }
}

原來用戶觸摸TP，會(huì)更新用戶行為的時(shí)間，那么用戶行為也會(huì)發(fā)生改變

private void updateUserActivitySummaryLocked(long now, int dirty) {
    // ...
    // 先移除更新用戶行為的定時(shí)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);
            // 用戶觸摸TP，更新了用戶行為時(shí)間 lastUserActivityTime，因此這里重新計(jì)算超時(shí)時(shí)間
            // 也就是說，延長了亮屏的時(shí)間
            if (lastUserActivityTime >= mLastWakeTime) {
                // 重新計(jì)算暗屏的超時(shí)時(shí)間
                groupNextTimeout = lastUserActivityTime + screenOffTimeout - screenDimDuration;
                if (now < groupNextTimeout) {
                    // 用戶行為是亮屏
                    groupUserActivitySummary = USER_ACTIVITY_SCREEN_BRIGHT;
                } else {
                    // ...
                }
            }
    }
    // ...
    // 再次發(fā)送定時(shí)消息，更新用戶行為
    if (hasUserActivitySummary && nextTimeout >= 0) {
        scheduleUserInactivityTimeout(nextTimeout);
    }        
}

由于用戶行為時(shí)間的更新，導(dǎo)致重新計(jì)算了暗屏的超時(shí)時(shí)間，并且用戶行為會(huì)更新為 USER_ACTIVITY_SCREEN_BRIGHT。

用戶行為的更新，也導(dǎo)致了請(qǐng)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，如果屏幕處于亮/暗狀態(tài)，用戶觸摸TP，請(qǐng)求策略更新為 DisplayPowerRequest.POLICY_BRIGHT，最終導(dǎo)致屏幕為亮屏狀態(tài)。

另外，重新計(jì)算出的暗屏超時(shí)時(shí)間，會(huì)被用來發(fā)送定時(shí)消息來更新用戶行為，因此就相當(dāng)于重置了屏幕超時(shí)時(shí)間。

因此，觸摸TP導(dǎo)致屏幕處于亮屏狀態(tài)，并且重置了屏幕超時(shí)時(shí)間，那么就相當(dāng)于延長了亮屏的時(shí)間。