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Android PowerManagerService省電模式策略控制

 更新時(shí)間：2022年08月24日 11:47:31   作者：大胃粥  
這篇文章主要介紹了Android PowerManagerService省電模式策略控制，本文基于前兩篇文章的基礎(chǔ)介紹展開(kāi)詳情，感興趣的小伙伴可以參考一下

前言

初識(shí)Android PowerManagerService省電模式 讓我們省電模式的概念有了初步的認(rèn)識(shí)，

Android PowerManagerService 打開(kāi)省電模式 對(duì)打開(kāi)省電模式的代碼進(jìn)行了分析。

有了前面兩篇文章的基礎(chǔ)，現(xiàn)在我們開(kāi)始分析如何控制省電模式策略，請(qǐng)讀者務(wù)必仔細(xì)。

本文涉及的文件如下：

  • frameworks/base/services/core/java/com/android/server/power/batterysaver/BatterySaverPolicy.java
  • frameworks/base/services/core/java/com/android/server/power/batterysaver/BatterySaverController.java

監(jiān)聽(tīng)策略改變

// BatterySaverPolicy.java

    public void systemReady() {
        ConcurrentUtils.wtfIfLockHeld(TAG, mLock);

        // 1. 監(jiān)聽(tīng) Global 數(shù)據(jù)
        // 當(dāng)數(shù)據(jù)改變，回調(diào) onChange()
        mContentResolver.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.BATTERY_SAVER_CONSTANTS), false, this);
        mContentResolver.registerContentObserver(Settings.Global.getUriFor(
                Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS), false, this);

        // 無(wú)障礙模式相關(guān)
        final AccessibilityManager acm = mContext.getSystemService(AccessibilityManager.class);
        acm.addAccessibilityStateChangeListener(enabled -> mAccessibilityEnabled.update(enabled));
        mAccessibilityEnabled.initialize(acm.isEnabled());

        // 車(chē)載相關(guān)
        UiModeManager uiModeManager = mContext.getSystemService(UiModeManager.class);
        uiModeManager.addOnProjectionStateChangedListener(UiModeManager.PROJECTION_TYPE_AUTOMOTIVE,
                mContext.getMainExecutor(), mOnProjectionStateChangedListener);
        mAutomotiveProjectionActive.initialize(
                uiModeManager.getActiveProjectionTypes() != UiModeManager.PROJECTION_TYPE_NONE);

        // 2. 監(jiān)聽(tīng) Config 表中，命名空間DeviceConfig.NAMESPACE_BATTERY_SAVER下的所有數(shù)據(jù)
        // 當(dāng)數(shù)據(jù)改變時(shí)，回調(diào) onPropertiesChanged()
        DeviceConfig.addOnPropertiesChangedListener(DeviceConfig.NAMESPACE_BATTERY_SAVER,
                mContext.getMainExecutor(), this);

        // 3. 讀取 Config 表中，命名空間DeviceConfig.NAMESPACE_BATTERY_SAVER下的所有數(shù)據(jù)
        mLastDeviceConfigProperties =
                DeviceConfig.getProperties(DeviceConfig.NAMESPACE_BATTERY_SAVER);

        // 4. 獲取 Global 表中的數(shù)據(jù)，并執(zhí)行更新操作
        onChange(true, null);
    }

前兩步是監(jiān)聽(tīng)數(shù)據(jù)，只不過(guò)回調(diào)的方式不同，但是最終都是根據(jù)數(shù)據(jù)更新省電模式策略，然后通知監(jiān)聽(tīng)者。

因此本文只分析其中一個(gè)回調(diào) onChange()，而另外一個(gè)回調(diào) onPropertiesChanged() 請(qǐng)讀者自行分析。

DeviceConfig 就是獲取 SettingsProvider 中 Config 表中的數(shù)據(jù)，這些數(shù)據(jù)的 KEY 以命名空間開(kāi)頭，然后把所有這些數(shù)據(jù)封裝成一個(gè) DeviceConfig.Properties 對(duì)象。

后兩步，是主動(dòng)獲取一次數(shù)據(jù)，然后主動(dòng)觸發(fā)一次 onChange() 回調(diào)。

// BatterySaverPolicy.java

    public void onChange(boolean selfChange, Uri uri) {
        refreshSettings();
    }
    private void refreshSettings() {
        synchronized (mLock) {
            // 1. 獲取與設(shè)備無(wú)關(guān)的省電模式策略
            // 例如，vibration_disabled=true,adjust_brightness_factor=0.5
            final String setting = getGlobalSetting(Settings.Global.BATTERY_SAVER_CONSTANTS);

            // 2. 獲取與設(shè)備相關(guān)的省電模式策略
            // 格式為, cpufreq-i=core-number:frequency/...,cpufreq-n=core-number:frequency/...
            String deviceSpecificSetting = getGlobalSetting(
                    Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS);

            // 保存與設(shè)備相關(guān)的省電模式策略的KEY值
            mDeviceSpecificSettingsSource =
                    Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS;

            // 3. 如果與設(shè)備相關(guān)的省電策略為空，那么加載 framework-res 的 config.xml 中的配置 config_batterySaverDeviceSpecificConfig
            if (TextUtils.isEmpty(deviceSpecificSetting) || "null".equals(deviceSpecificSetting)) {
                // 配置默認(rèn)也為空
                deviceSpecificSetting =
                        mContext.getString(getDeviceSpecificConfigResId());
                // 表示是從配置文件中配置的
                mDeviceSpecificSettingsSource = "(overlay)";
            }


            // 4. 更新策略
            if (!updateConstantsLocked(setting, deviceSpecificSetting)) {
                // 沒(méi)有變化，就不去執(zhí)行后面的通知監(jiān)聽(tīng)者的操作
                return;
            }
        }

        // 5. 如果策略改變，通知監(jiān)聽(tīng)者
        maybeNotifyListenersOfPolicyChange();
    }

Settings.Global.BATTERY_SAVER_CONSTANTS 保存的是與設(shè)備無(wú)關(guān)的省電策略。例如，這個(gè)字段的值可以為 vibration_disabled=true,adjust_brightness_factor=0.5，不同的策略通過(guò)逗號(hào)進(jìn)行分隔。從名字可以猜測(cè)出，前一個(gè)省電策略表示關(guān)閉振動(dòng)，后一個(gè)省電策略表示屏幕亮度降低一半。

什么叫與設(shè)備無(wú)關(guān)策略？如果這個(gè)省電策略不會(huì)因設(shè)備不同而不同的話(huà)，那這個(gè)策略就是與設(shè)備無(wú)關(guān)，反之就是與設(shè)備有關(guān)策略。

Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS 保存的是與設(shè)備相關(guān)的省點(diǎn)策略，目前只保存 CPU 限頻策略。 這個(gè)字段的值可能為 cpufreq-i=core-number:frequency,cpufreq-n=core-number:frequency，其中 cpufreq-i 表示交互狀態(tài)下的CPU限頻策略，cpufreq-n 表示非交互狀態(tài)下的CPU限頻策略，core-number 表示 CPU 編號(hào)，frequency 表示需要限制的頻率。交互狀態(tài)和非交互狀態(tài)的限頻策略以逗號(hào)進(jìn)行分隔。

當(dāng)然，在省電模式下，不一定只限制一個(gè)CPU的頻率，我們可以使用 / 來(lái)分隔不同的 CPU 限頻策略，例如 cpufreq-i=core-number:frequency/core-number:frequency/core-number:frequency.

通常，亮屏狀態(tài)下為交互模式，滅屏狀態(tài)下為非交互模式。

從第三步中可以看出，可以在 framework-res 模塊的 config.xml 中配置 CPU 限頻策略。記住這里，不要看完了我一系列的省電模式的文章，最終連 CPU 限頻策略還不會(huì)配置哦!

第四步，會(huì)根據(jù)這些數(shù)據(jù)來(lái)更新省電模式策略。并且，如果省電模式策略改變了，那么還會(huì)執(zhí)行第五步，通知監(jiān)聽(tīng)者。

下面，重點(diǎn)分析第四步和第五步。

更新策略

現(xiàn)在，假設(shè) Settings.Global.BATTERY_SAVER_CONSTANTS 和 Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS 保存的數(shù)據(jù)改變了，那么會(huì)調(diào)用 updateConstantsLocked() 更新省電模式策略

// BatterySaverPolicy.java

    boolean updateConstantsLocked(String setting, String deviceSpecificSetting) {
        // 如果是null，返回""
        setting = TextUtils.emptyIfNull(setting);
        deviceSpecificSetting = TextUtils.emptyIfNull(deviceSpecificSetting);
        // 沒(méi)有變化，直接返回
        if (setting.equals(mSettings)
                && deviceSpecificSetting.equals(mDeviceSpecificSettings)) {
            return false;
        }
        // 1. 保存設(shè)置
        mSettings = setting;
        mDeviceSpecificSettings = deviceSpecificSetting;
        // 2. 根據(jù)配置，創(chuàng)建新的策略
        Poilcy p = Policy.fromSettings(setting, deviceSpecificSetting, mLastDeviceConfigProperties, null, DEFAULT_FULL_POLICY);

        // 3. 更新默認(rèn)的省電模式策略
        boolean changed = maybeUpdateDefaultFullPolicy(p);

        // 忽略 adaptive battery save 功能
        mDefaultAdaptivePolicy = Policy.fromSettings("", "",
                mLastDeviceConfigProperties, KEY_SUFFIX_ADAPTIVE, DEFAULT_ADAPTIVE_POLICY);
        if (mPolicyLevel == POLICY_LEVEL_ADAPTIVE
                && !mAdaptivePolicy.equals(mDefaultAdaptivePolicy)) {
            // adaptive policy changed
            changed = true;
        }
        mAdaptivePolicy = mDefaultAdaptivePolicy;

        // 4. 更新有效的省電模式策略
        updatePolicyDependenciesLocked();

        // 5. 返回狀態(tài)，表示省電模式策略是否改變
        return changed;
    }

第二步，根據(jù)配置的數(shù)據(jù)創(chuàng)建一個(gè)策略，注意最后一個(gè)參數(shù) DEFAULT_FULL_POLICY，它表示默認(rèn)的省電模式策略

// BatterySaverPolicy.java

        private static Policy fromSettings(String settings, String deviceSpecificSettings,
                DeviceConfig.Properties properties, String configSuffix, Policy defaultPolicy) {
            // 以逗號(hào)為分隔符解析字符串
            final KeyValueListParser parser = new KeyValueListParser(',');
            configSuffix = TextUtils.emptyIfNull(configSuffix);

            // 1. 首先解析設(shè)備相關(guān)的策略參數(shù)
            try {
                parser.setString(deviceSpecificSettings == null ? "" : deviceSpecificSettings);
            } catch (IllegalArgumentException e) {
                Slog.wtf(TAG, "Bad device specific battery saver constants: "
                        + deviceSpecificSettings);
            }
            // 讀取的值的格式為 core-number:frequency/core-number:frequency/...
            final String cpuFreqInteractive = parser.getString(KEY_CPU_FREQ_INTERACTIVE, "");
            final String cpuFreqNoninteractive = parser.getString(KEY_CPU_FREQ_NONINTERACTIVE, "");


            // 2. 再解析設(shè)備無(wú)關(guān)的策略參數(shù)
            try {
                parser.setString(settings == null ? "" : settings);
            } catch (IllegalArgumentException e) {
                Slog.wtf(TAG, "Bad battery saver constants: " + settings);
            }

            // 策略參數(shù)取值的優(yōu)先級(jí)為: Settings > DeviceConfig > 默認(rèn)省電策略
            final float adjustBrightnessFactor = parser.getFloat(KEY_ADJUST_BRIGHTNESS_FACTOR,
                    properties.getFloat(KEY_ADJUST_BRIGHTNESS_FACTOR + configSuffix,
                            defaultPolicy.adjustBrightnessFactor));
            final boolean advertiseIsEnabled = parser.getBoolean(KEY_ADVERTISE_IS_ENABLED,
                    properties.getBoolean(KEY_ADVERTISE_IS_ENABLED + configSuffix,
                            defaultPolicy.advertiseIsEnabled));
            final boolean deferFullBackup = parser.getBoolean(KEY_DEFER_FULL_BACKUP,
                    properties.getBoolean(KEY_DEFER_FULL_BACKUP + configSuffix,
                            defaultPolicy.deferFullBackup));
            final boolean deferKeyValueBackup = parser.getBoolean(KEY_DEFER_KEYVALUE_BACKUP,
                    properties.getBoolean(KEY_DEFER_KEYVALUE_BACKUP + configSuffix,
                            defaultPolicy.deferKeyValueBackup));
            final boolean disableAnimation = parser.getBoolean(KEY_DISABLE_ANIMATION,
                    properties.getBoolean(KEY_DISABLE_ANIMATION + configSuffix,
                            defaultPolicy.disableAnimation));
            final boolean disableAod = parser.getBoolean(KEY_DISABLE_AOD,
                    properties.getBoolean(KEY_DISABLE_AOD + configSuffix,
                            defaultPolicy.disableAod));
            final boolean disableLaunchBoost = parser.getBoolean(KEY_DISABLE_LAUNCH_BOOST,
                    properties.getBoolean(KEY_DISABLE_LAUNCH_BOOST + configSuffix,
                            defaultPolicy.disableLaunchBoost));
            final boolean disableOptionalSensors = parser.getBoolean(KEY_DISABLE_OPTIONAL_SENSORS,
                    properties.getBoolean(KEY_DISABLE_OPTIONAL_SENSORS + configSuffix,
                            defaultPolicy.disableOptionalSensors));
            final boolean disableVibrationConfig = parser.getBoolean(KEY_DISABLE_VIBRATION,
                    properties.getBoolean(KEY_DISABLE_VIBRATION + configSuffix,
                            defaultPolicy.disableVibration));
            final boolean enableBrightnessAdjustment = parser.getBoolean(
                    KEY_ENABLE_BRIGHTNESS_ADJUSTMENT,
                    properties.getBoolean(KEY_ENABLE_BRIGHTNESS_ADJUSTMENT + configSuffix,
                            defaultPolicy.enableAdjustBrightness));
            final boolean enableDataSaver = parser.getBoolean(KEY_ENABLE_DATASAVER,
                    properties.getBoolean(KEY_ENABLE_DATASAVER + configSuffix,
                            defaultPolicy.enableDataSaver));
            final boolean enableFirewall = parser.getBoolean(KEY_ENABLE_FIREWALL,
                    properties.getBoolean(KEY_ENABLE_FIREWALL + configSuffix,
                            defaultPolicy.enableFirewall));
            final boolean enableNightMode = parser.getBoolean(KEY_ENABLE_NIGHT_MODE,
                    properties.getBoolean(KEY_ENABLE_NIGHT_MODE + configSuffix,
                            defaultPolicy.enableNightMode));
            final boolean enableQuickDoze = parser.getBoolean(KEY_ENABLE_QUICK_DOZE,
                    properties.getBoolean(KEY_ENABLE_QUICK_DOZE + configSuffix,
                            defaultPolicy.enableQuickDoze));
            final boolean forceAllAppsStandby = parser.getBoolean(KEY_FORCE_ALL_APPS_STANDBY,
                    properties.getBoolean(KEY_FORCE_ALL_APPS_STANDBY + configSuffix,
                            defaultPolicy.forceAllAppsStandby));
            final boolean forceBackgroundCheck = parser.getBoolean(KEY_FORCE_BACKGROUND_CHECK,
                    properties.getBoolean(KEY_FORCE_BACKGROUND_CHECK + configSuffix,
                            defaultPolicy.forceBackgroundCheck));
            final int locationMode = parser.getInt(KEY_LOCATION_MODE,
                    properties.getInt(KEY_LOCATION_MODE + configSuffix,
                            defaultPolicy.locationMode));
            final int soundTriggerMode = parser.getInt(KEY_SOUNDTRIGGER_MODE,
                    properties.getInt(KEY_SOUNDTRIGGER_MODE + configSuffix,
                            defaultPolicy.soundTriggerMode));

            // 3. 創(chuàng)建一個(gè)新的策略
            return new Policy(
                    adjustBrightnessFactor,
                    advertiseIsEnabled,
                    (new CpuFrequencies()).parseString(cpuFreqInteractive),
                    (new CpuFrequencies()).parseString(cpuFreqNoninteractive),
                    deferFullBackup,
                    deferKeyValueBackup,
                    disableAnimation,
                    disableAod,
                    disableLaunchBoost,
                    disableOptionalSensors,
                    /* disableVibration */
                    disableVibrationConfig,
                    enableBrightnessAdjustment,
                    enableDataSaver,
                    enableFirewall,
                    enableNightMode,
                    enableQuickDoze,
                    forceAllAppsStandby,
                    forceBackgroundCheck,
                    locationMode,
                    soundTriggerMode
            );
        }

與設(shè)備相關(guān)的省電策略，也就是 CPU 限頻策略，如果空缺，也不會(huì)被任何配置取代。

與設(shè)備無(wú)關(guān)的省電策略，如果某一項(xiàng)空缺，會(huì)依次被 DeviceConfig 和 默認(rèn)的省電策略 DEFAULT_FULL_POLICY 取代。

最終通過(guò)解析的數(shù)據(jù)，創(chuàng)建一個(gè)策略 Policy 對(duì)象。

新的策略已經(jīng)創(chuàng)建出來(lái)，之后調(diào)用 maybeUpdateDefaultFullPolicy() 更新默認(rèn)的省電策略。

// BatterySaverPolicy.java

    private boolean maybeUpdateDefaultFullPolicy(Policy p) {
        boolean fullPolicyChanged = false;
        if (!mDefaultFullPolicy.equals(p)) {
            // mFullPolicy 會(huì)被 setFullPolicyLocked() 修改
            // 如果 mFullPolicy 與 mDefaultFullPolicy 不同, 那么表示 mFullPolicy 被覆蓋
            // 如果相同，表示沒(méi)有被覆蓋
            boolean isDefaultFullPolicyOverridden = !mDefaultFullPolicy.equals(mFullPolicy);
            if (!isDefaultFullPolicyOverridden) {
                // mFullPolicy 沒(méi)有被覆蓋，就要同步進(jìn)行更新
                mFullPolicy = p;
                // 現(xiàn)在處于省電模式中，需要通知監(jiān)聽(tīng)者
                fullPolicyChanged = (mPolicyLevel == POLICY_LEVEL_FULL);
            }
            // 更新默認(rèn)的省電模式策略
            mDefaultFullPolicy = p;
        }

        return fullPolicyChanged;
    }

mDefaultFullPolicy 代表的就是默認(rèn)的省電策略，這里會(huì)更新它，但是同時(shí)，如果 mFullPolicy 沒(méi)有被 setFullPolicyLocked() 修改(源碼設(shè)計(jì)中稱(chēng)之為 overridden)，那么也會(huì)同步更新它。

現(xiàn)在默認(rèn)的省點(diǎn)策略已經(jīng)更新，但是要應(yīng)用的最終策略還不是它，需要調(diào)用 updatePolicyDependenciesLocked() 來(lái)根據(jù)情況，更新一個(gè)有效的省點(diǎn)策略

// BatterySaverPolicy.java
    private void updatePolicyDependenciesLocked() {
        final Policy rawPolicy = getCurrentRawPolicyLocked();
        final int locationMode;
        invalidatePowerSaveModeCaches();
        if (mAutomotiveProjectionActive.get()
                && rawPolicy.locationMode != PowerManager.LOCATION_MODE_NO_CHANGE
                && rawPolicy.locationMode != PowerManager.LOCATION_MODE_FOREGROUND_ONLY) {
            // If car projection is enabled, ensure that navigation works.
            locationMode = PowerManager.LOCATION_MODE_FOREGROUND_ONLY;
        } else {
            locationMode = rawPolicy.locationMode;
        }
        mEffectivePolicyRaw = new Policy(
                rawPolicy.adjustBrightnessFactor,
                rawPolicy.advertiseIsEnabled,
                rawPolicy.cpuFrequenciesForInteractive,
                rawPolicy.cpuFrequenciesForNoninteractive,
                rawPolicy.deferFullBackup,
                rawPolicy.deferKeyValueBackup,
                rawPolicy.disableAnimation,
                rawPolicy.disableAod,
                rawPolicy.disableLaunchBoost,
                rawPolicy.disableOptionalSensors,
                // Don't disable vibration when accessibility is on.
                rawPolicy.disableVibration && !mAccessibilityEnabled.get(),
                rawPolicy.enableAdjustBrightness,
                rawPolicy.enableDataSaver,
                rawPolicy.enableFirewall,
                // Don't force night mode when car projection is enabled.
                rawPolicy.enableNightMode && !mAutomotiveProjectionActive.get(),
                rawPolicy.enableQuickDoze,
                rawPolicy.forceAllAppsStandby,
                rawPolicy.forceBackgroundCheck,
                locationMode,
                rawPolicy.soundTriggerMode
        );
        // ...
    }

很簡(jiǎn)單，根據(jù)是否是車(chē)載項(xiàng)目，以及是否打開(kāi)無(wú)障礙模式，更新有效的省電模式策略 mEffectivePolicyRaw。

通知監(jiān)聽(tīng)者

現(xiàn)在省電策略已經(jīng)更新完畢，如果策略改變了，那么需要通知監(jiān)聽(tīng)者

// BatterySaverPolicy.java

    private void maybeNotifyListenersOfPolicyChange() {
        final BatterySaverPolicyListener[] listeners;
        synchronized (mLock) {
            if (mPolicyLevel == POLICY_LEVEL_OFF) {
                // 省電模式?jīng)]有打開(kāi)
                return;
            }
            // Don't call out to listeners with the lock held.
            listeners = mListeners.toArray(new BatterySaverPolicyListener[mListeners.size()]);
        }

        mHandler.post(() -> {
            for (BatterySaverPolicyListener listener : listeners) {
                // 通知監(jiān)聽(tīng)者
                listener.onBatterySaverPolicyChanged(this);
            }
        });
    }

目前，省電策略的監(jiān)聽(tīng)者只有一個(gè) BatterySaverController

// BatterySaverController.java

    public void onBatterySaverPolicyChanged(BatterySaverPolicy policy) {
        if (!isPolicyEnabled()) {
            return; // No need to send it if not enabled.
        }
        mHandler.postStateChanged(/*sendBroadcast=*/ true, REASON_POLICY_CHANGED);
    }

最終會(huì)調(diào)用 handleBatterySaverStateChanged()

// BatterySaverController.java

    void handleBatterySaverStateChanged(boolean sendBroadcast, int reason) {
        final LowPowerModeListener[] listeners;
        final boolean enabled;
        final boolean isInteractive = getPowerManager().isInteractive();
        final ArrayMap<String, String> fileValues;
        synchronized (mLock) {
            enabled = getFullEnabledLocked() || getAdaptiveEnabledLocked();

            mFullPreviouslyEnabled = getFullEnabledLocked();
            mAdaptivePreviouslyEnabled = getAdaptiveEnabledLocked();

            listeners = mListeners.toArray(new LowPowerModeListener[0]);

            mIsInteractive = isInteractive;

            // 1. 獲取CPU限頻策略
            if (enabled) {
                fileValues = mBatterySaverPolicy.getFileValues(isInteractive);
            } else {
                fileValues = null;
            }
        }

        final PowerManagerInternal pmi = LocalServices.getService(PowerManagerInternal.class);
        if (pmi != null) {
            pmi.setPowerMode(Mode.LOW_POWER, isEnabled());
        }

        updateBatterySavingStats();

        // 2. 應(yīng)用CPU限頻策略
        if (ArrayUtils.isEmpty(fileValues)) {
            // 如果策略為空，那肯定是關(guān)閉了省電模式，此時(shí)需要恢復(fù)正常的CPU頻率
            mFileUpdater.restoreDefault();
        } else {
            // 策略不為空，首先保存節(jié)點(diǎn)中原本的值到 /data/system/battery-saver/default-values.xml，然后向節(jié)點(diǎn)寫(xiě)值
            mFileUpdater.writeFiles(fileValues);
        }

        if (sendBroadcast) {
            // 3. 發(fā)送廣播
            Intent intent = new Intent(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED);
            intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
            mContext.sendBroadcastAsUser(intent, UserHandle.ALL);

            // Send the broadcast to a manifest-registered receiver that is specified in the config.
            if (getPowerSaveModeChangedListenerPackage().isPresent()) {
                intent = new Intent(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED)
                        .setPackage(getPowerSaveModeChangedListenerPackage().get())
                        .addFlags(Intent.FLAG_RECEIVER_INCLUDE_BACKGROUND
                                | Intent.FLAG_RECEIVER_FOREGROUND);
                mContext.sendBroadcastAsUser(intent, UserHandle.ALL);
            }

            // Send internal version that requires signature permission.
            intent = new Intent(PowerManager.ACTION_POWER_SAVE_MODE_CHANGED_INTERNAL);
            intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
            mContext.sendBroadcastAsUser(intent, UserHandle.ALL,
                    Manifest.permission.DEVICE_POWER);

            // 4. 通知監(jiān)聽(tīng)者，省電策略已經(jīng)改變
            for (LowPowerModeListener listener : listeners) {
                final PowerSaveState result =
                        mBatterySaverPolicy.getBatterySaverPolicy(listener.getServiceType());
                listener.onLowPowerModeChanged(result);
            }
        }
    }

這段代碼，我只分析如何應(yīng)用省電策略。

第一步，是獲取 CPU 限頻策略，以一個(gè) Map 表示，其中 KEY 為 CPU 限頻的節(jié)點(diǎn)路徑，VALUE 為被限制的頻率。

然后第二步是應(yīng)用這個(gè) CPU 限頻策略，其實(shí)就是向節(jié)點(diǎn)寫(xiě)值。 不過(guò)在寫(xiě)值之前，會(huì)先保存節(jié)點(diǎn)中原本的值到 /data/system/battery-saver/default-values.xml 文件中，這個(gè)文件的作用是，當(dāng)關(guān)閉省電模式，會(huì)恢復(fù) CPU 原本的頻率。

最后，通知監(jiān)聽(tīng)者，策略已經(jīng)改變，你們需要做相應(yīng)的適配。這些監(jiān)聽(tīng)者都是系統(tǒng)服務(wù)，例如WindowManagerService 就是一個(gè)監(jiān)聽(tīng)者，它會(huì)根據(jù)省電模式策略，決定是否關(guān)閉動(dòng)畫(huà)，關(guān)鍵代碼如下：

                case NEW_ANIMATOR_SCALE: {
                    // 省電模式下，scale 為 0
                    float scale = getCurrentAnimatorScale();
                    // 關(guān)閉 system_server 進(jìn)程的動(dòng)畫(huà)
                    ValueAnimator.setDurationScale(scale);
                    Session session = (Session)msg.obj;
                    if (session != null) {
                        try {
                            session.mCallback.onAnimatorScaleChanged(scale);
                        } catch (RemoteException e) {
                        }
                    } else {
                        ArrayList<IWindowSessionCallback> callbacks
                                = new ArrayList<IWindowSessionCallback>();
                        synchronized (mGlobalLock) {
                            for (int i=0; i<mSessions.size(); i++) {
                                callbacks.add(mSessions.valueAt(i).mCallback);
                            }

                        }
                        for (int i=0; i<callbacks.size(); i++) {
                            try {
                                // 關(guān)閉 app 進(jìn)程的動(dòng)畫(huà)
                                callbacks.get(i).onAnimatorScaleChanged(scale);
                            } catch (RemoteException e) {
                            }
                        }
                    }
                    break;
                }

如何配置策略

看完了策略控制的源碼分析，總結(jié)下如何控制策略

  • 修改 Settings.Global.BATTERY_SAVER_CONSTANTS 字段值，可以設(shè)置的字參考注釋文檔，或者參考源碼的解析部分。例如 vibration_disabled=true,adjust_brightness_factor=0.5
  • 修改 Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS字段值，但是這個(gè)只能修改 CPU 限頻策略。例如 cpufreq-i=0:1804810/1:1804900,cpufreq-n=0:1804700/1:1804600。
  • 可以通過(guò) framework-res 的 config.xml 的config_batterySaverDeviceSpecificConfig 配置默認(rèn)的 CPU 限頻策略。但是這個(gè)會(huì)被 Settings.Global.BATTERY_SAVER_DEVICE_SPECIFIC_CONSTANTS 覆蓋，在有值的情況下。

結(jié)束

省電模式的文章，到此就結(jié)束了。本來(lái)我還準(zhǔn)備分析省電模式影響的功能，但是由于影響的功能有點(diǎn)多，但是我又無(wú)法精通所有的功能，因此我就不獻(xiàn)丑了去分析了。

在工作中，如果你熟悉的某個(gè)功能模塊，例如 WindowManagerService，它受省電模式影響，我相信，如果你看完我的文章，應(yīng)該能自行分析受影響的功能。

到此這篇關(guān)于Android PowerManagerService省電模式策略控制的文章就介紹到這了,更多相關(guān)Android PowerManagerService 內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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