# 前言

由于源码分析的代码量比较大，大部分博客网站的内容显示页面都比较窄，显示出来的效果都异常丑陋，所以您也可以直接查看 《 Thinking in Android 》 来阅读这边文章，希望这篇文章能帮你梳理清楚 “Android 关机流程”。

# 核心源码

关键类	路径
GlobalActions.java	frameworks/base/services/core/java/com/android/server/policy/GlobalActions.java
LegacyGlobalActions.java	frameworks/base/services/core/java/com/android/server/policy/LegacyGlobalActions.java
PhoneWindowManager.java	frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java
PowerManagerService.java	frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java
ShutdownThread.java	frameworks/base/services/core/java/com/android/server/power/ShutdownThread.java
WindowManagerService.java	frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java

一、PhoneWindowManager

Android 系统的关机流程是从用户按 power 键开始的，所有的按键处理都是通过 PhoneWindowManager.interceptKeyBeforeQueueing() 方法进行处理。

2.1 PhoneWindowManager.interceptKeyBeforeQueueing()

// frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.javapublic class PhoneWindowManager implements WindowManagerPolicy {@Overridepublic int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {... ...// Handle special keys.switch (keyCode) {... ...case KeyEvent.KEYCODE_POWER: {EventLogTags.writeInterceptPower(KeyEvent.actionToString(event.getAction()),mPowerKeyHandled ? 1 : 0, mPowerKeyPressCounter);// Any activity on the power button stops the accessibility shortcutcancelPendingAccessibilityShortcutAction();result &= ~ACTION_PASS_TO_USER;isWakeKey = false; // wake-up will be handled separatelyif (down) {// down 为 true，代表按下 power 键，走 interceptPowerKeyDown() 方法interceptPowerKeyDown(event, interactive);} else {interceptPowerKeyUp(event, interactive, canceled);}break;}... ...}}

2.2 PhoneWindowManager.interceptPowerKeyDown()

// frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.javapublic class PhoneWindowManager implements WindowManagerPolicy {private void interceptPowerKeyDown(KeyEvent event, boolean interactive) {... ...// 截屏功能if (interactive && !mScreenshotChordPowerKeyTriggered&& (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {mScreenshotChordPowerKeyTriggered = true;mScreenshotChordPowerKeyTime = event.getDownTime();interceptScreenshotChord();interceptRingerToggleChord();}TelecomManager telecomManager = getTelecommService();boolean hungUp = false;if (telecomManager != null) {if (telecomManager.isRinging()) {telecomManager.silenceRinger();    // 如果来电时，按 Power 则静音} else if ((mIncallPowerBehavior& Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != 0&& telecomManager.isInCall() && interactive) {hungUp = telecomManager.endCall();}}... ...mPowerKeyHandled = hungUp || mScreenshotChordVolumeDownKeyTriggered|| mA11yShortcutChordVolumeUpKeyTriggered || gesturedServiceIntercepted;if (!mPowerKeyHandled) {if (interactive) {if (hasLongPressOnPowerBehavior()) {if ((event.getFlags() & KeyEvent.FLAG_LONG_PRESS) != 0) {powerLongPress();    // 长按 Power 键，核心方法} else {... ...}}} else {wakeUpFromPowerKey(event.getDownTime());if (mSupportLongPressPowerWhenNonInteractive && hasLongPressOnPowerBehavior()) {if ((event.getFlags() & KeyEvent.FLAG_LONG_PRESS) != 0) {powerLongPress();    // 长按 Power 键，核心方法} else {... ...}mBeganFromNonInteractive = true;} else {... ...}}}}}

2.3 PhoneWindowManager.powerLongPress()

// frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.javapublic class PhoneWindowManager implements WindowManagerPolicy {private void powerLongPress() {final int behavior = getResolvedLongPressOnPowerBehavior();    // 得到长按电源键的行为switch (behavior) {case LONG_PRESS_POWER_NOTHING:break;case LONG_PRESS_POWER_GLOBAL_ACTIONS:    // 原生的会走这个 casemPowerKeyHandled = true;performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);showGlobalActionsInternal();         // 调用 showGlobalActionsInternal() 方法break;... ...}}}

powerLongPress() 有两个核心方法，getResolvedLongPressOnPowerBehavior() 和 showGlobalActionsInternal()，我们分别看下。

2.4 PhoneWindowManager.getResolvedLongPressOnPowerBehavior()

// frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.javapublic class PhoneWindowManager implements WindowManagerPolicy {int mLongPressOnPowerBehavior;mLongPressOnPowerBehavior = mContext.getResources().getInteger(com.android.internal.R.integer.config_longPressOnPowerBehavior);private int getResolvedLongPressOnPowerBehavior() {if (FactoryTest.isLongPressOnPowerOffEnabled()) {return LONG_PRESS_POWER_SHUT_OFF_NO_CONFIRM;}return mLongPressOnPowerBehavior;    // 返回 config_longPressOnPowerBehavior 的值}}

其实就是获取 config_longPressOnPowerBehavior 的值，这个值是什么？

// frameworks/base/core/res/res/values/config.xml<!-- Control the behavior when the user long presses the power button.0 - Nothing                             // 表示直接关机1 - Global actions menu                 // 关机要显示 Global actions2 - Power off (with confirmation)       // 关机要弹出对话框再次确认3 - Power off (without confirmation)    // 关机不需要弹出对话框4 - Go to voice assist
-->
<integer name="config_longPressOnPowerBehavior">1</integer>    // 可设置默认值

2.5 PhoneWindowManager.showGlobalActionsInternal()

// frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.javapublic class PhoneWindowManager implements WindowManagerPolicy {void showGlobalActionsInternal() {if (mGlobalActions == null) {mGlobalActions = new GlobalActions(mContext, mWindowManagerFuncs);}final boolean keyguardShowing = isKeyguardShowingAndNotOccluded();mGlobalActions.showDialog(keyguardShowing, isDeviceProvisioned());    // 弹出关机的对话框// since it took two seconds of long press to bring this up,// poke the wake lock so they have some time to see the dialog.mPowerManager.userActivity(SystemClock.uptimeMillis(), false);}}

2.6 GlobalActions.showDialog()

// frameworks/base/services/core/java/com/android/server/policy/GlobalActions.javaclass GlobalActions implements GlobalActionsProvider.GlobalActionsListener {private LegacyGlobalActions mLegacyGlobalActions;public void showDialog(boolean keyguardShowing, boolean deviceProvisioned) {if (DEBUG) Slog.d(TAG, "showDialog " + keyguardShowing + " " + deviceProvisioned);if (mGlobalActionsProvider != null && mGlobalActionsProvider.isGlobalActionsDisabled()) {return;}mKeyguardShowing = keyguardShowing;mDeviceProvisioned = deviceProvisioned;mShowing = true;if (mGlobalActionsAvailable) {mHandler.postDelayed(mShowTimeout, 5000);mGlobalActionsProvider.showGlobalActions();} else {// SysUI isn't alive, show legacy menu.ensureLegacyCreated();// 调用 LegacyGlobalActions.showDialog() 方法mLegacyGlobalActions.showDialog(mKeyguardShowing, mDeviceProvisioned);}}}

2.7 LegacyGlobalActions.showDialog()

// frameworks/base/services/core/java/com/android/server/policy/LegacyGlobalActions.javaclass LegacyGlobalActions implements DialogInterface.OnDismissListener, DialogInterface.OnClickListener  {public void showDialog(boolean keyguardShowing, boolean isDeviceProvisioned) {mKeyguardShowing = keyguardShowing;mDeviceProvisioned = isDeviceProvisioned;if (mDialog != null) {mDialog.dismiss();mDialog = null;// Show delayed, so that the dismiss of the previous dialog completesmHandler.sendEmptyMessage(MESSAGE_SHOW);} else {handleShow();    // 如果 Dialog 不为空，则创建}}}

2.8 LegacyGlobalActions.handleShow()

// frameworks/base/services/core/java/com/android/server/policy/LegacyGlobalActions.javaclass LegacyGlobalActions implements DialogInterface.OnDismissListener, DialogInterface.OnClickListener  {private void handleShow() {awakenIfNecessary();mDialog = createDialog();prepareDialog();// If we only have 1 item and it's a simple press action, just do this action.if (mAdapter.getCount() == 1&& mAdapter.getItem(0) instanceof SinglePressAction&& !(mAdapter.getItem(0) instanceof LongPressAction)) {((SinglePressAction) mAdapter.getItem(0)).onPress();    // 调用 onPress() 方法} else {if (mDialog != null) {WindowManager.LayoutParams attrs = mDialog.getWindow().getAttributes();attrs.setTitle("LegacyGlobalActions");mDialog.getWindow().setAttributes(attrs);mDialog.show();mDialog.getWindow().getDecorView().setSystemUiVisibility(View.STATUS_BAR_DISABLE_EXPAND);}}}}

当点击 dialog 的 power off 时，会调用 PowerAction 的 onPress() 方法。

2.9 PowerAction.onPress()

// frameworks/base/services/core/java/com/android/server/policy/PowerAction.javapublic final class PowerAction extends SinglePressAction implements LongPressAction {@Overridepublic void onPress() {// shutdown by making sure radio and power are handled accordingly.mWindowManagerFuncs.shutdown(false /* confirm */);    // 调用 WindowManagerService.shutdown() 方法}}

2.10 WindowManagerService.shutdown()

// frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.javapublic class WindowManagerService extends IWindowManager.Stubimplements Watchdog.Monitor, WindowManagerPolicy.WindowManagerFuncs {// Called by window manager policy.  Not exposed externally.@Overridepublic void shutdown(boolean confirm) {// Pass in the UI context, since ShutdownThread requires it (to show UI).// 调用 ShutdownThread.shutdown() 方法ShutdownThread.shutdown(ActivityThread.currentActivityThread().getSystemUiContext(),PowerManager.SHUTDOWN_USER_REQUESTED, confirm);}}

三、ShutdownThread

Android 关机的流程最终是通过 ShutdownThread 线程实现。

3.1 ShutdownThread.shutdown()

// frameworks/base/services/core/java/com/android/server/power/ShutdownThread.javapublic final class ShutdownThread extends Thread {public static void shutdown(final Context context, String reason, boolean confirm) {mReboot = false;mRebootSafeMode = false;mReason = reason;shutdownInner(context, confirm);    // 内部调用 shutdownInner() 方法}}

3.2 ShutdownThread.shutdownInner()

// frameworks/base/services/core/java/com/android/server/power/ShutdownThread.javapublic final class ShutdownThread extends Thread {private static void shutdownInner(final Context context, boolean confirm) {context.assertRuntimeOverlayThemable();synchronized (sIsStartedGuard) {if (sIsStarted) {Log.d(TAG, "Request to shutdown already running, returning.");return;}}// 获取用户长按 Power 键的处理行为final int longPressBehavior = context.getResources().getInteger(com.android.internal.R.integer.config_longPressOnPowerBehavior);final int resourceId = mRebootSafeMode? com.android.internal.R.string.reboot_safemode_confirm: (longPressBehavior == 2? com.android.internal.R.string.shutdown_confirm_question: com.android.internal.R.string.shutdown_confirm);Log.d(TAG, "Notifying thread to start shutdown longPressBehavior=" + longPressBehavior);if (confirm) {    // 弹出关机、重启对话框，供用户选择final CloseDialogReceiver closer = new CloseDialogReceiver(context);    // 注册关机对话框广播if (sConfirmDialog != null) {sConfirmDialog.dismiss();}// 创建关机 DialogsConfirmDialog = new AlertDialog.Builder(context).setTitle(mRebootSafeMode? com.android.internal.R.string.reboot_safemode_title: com.android.internal.R.string.power_off).setMessage(resourceId).setPositiveButton(com.android.internal.R.string.yes, new DialogInterface.OnClickListener() {public void onClick(DialogInterface dialog, int which) {beginShutdownSequence(context);    // 执行 beginShutdownSequence() 方法，开始关机流程}}).setNegativeButton(com.android.internal.R.string.no, null).create();closer.dialog = sConfirmDialog;sConfirmDialog.setOnDismissListener(closer);sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);sConfirmDialog.show();} else {beginShutdownSequence(context);}}}

3.3 ShutdownThread.beginShutdownSequence()

// frameworks/base/services/core/java/com/android/server/power/ShutdownThread.javapublic final class ShutdownThread extends Thread {// static instance of this threadprivate static final ShutdownThread sInstance = new ShutdownThread();// 我们一般可以在这个方法里面添加关机动画private static void beginShutdownSequence(Context context) {synchronized (sIsStartedGuard) {if (sIsStarted) {Log.d(TAG, "Shutdown sequence already running, returning.");return;}sIsStarted = true;}sInstance.mProgressDialog = showShutdownDialog(context);    // 显示关机进度对话框sInstance.mContext = context;sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);... ...// // start the thread that initiates shutdown -- 启动关机线程 ，执行 Run 方法sInstance.mHandler = new Handler() {};sInstance.start();}}

3.4 ShutdownThread.run()

启动关机线程，执行 run();

// frameworks/base/services/core/java/com/android/server/power/ShutdownThread.javapublic final class ShutdownThread extends Thread {public void run() {... ...{String reason = (mReboot ? "1" : "0") + (mReason != null ? mReason : "");SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);    // 保存关机的原因}if (mRebootSafeMode) {SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");}... ...// First send the high-level shut down broadcast.mActionDone = false;Intent intent = new Intent(Intent.ACTION_SHUTDOWN);intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND | Intent.FLAG_RECEIVER_REGISTERED_ONLY);// 发送关机广播mContext.sendOrderedBroadcastAsUser(intent, UserHandle.ALL, null, br, mHandler, 0, null, null);final long endTime = SystemClock.elapsedRealtime() + MAX_BROADCAST_TIME;... ...if (mRebootHasProgressBar) {sInstance.setRebootProgress(BROADCAST_STOP_PERCENT, null);}shutdownTimingLog.traceEnd(); // SendShutdownBroadcast -- 关机广播所用的时间... ...final IActivityManager am = IActivityManager.Stub.asInterface(ServiceManager.checkService("activity"));if (am != null) {try {am.shutdown(MAX_BROADCAST_TIME);    // 关闭 ActivityManagerService 服务} catch (RemoteException e) {}}if (mRebootHasProgressBar) {sInstance.setRebootProgress(ACTIVITY_MANAGER_STOP_PERCENT, null);}shutdownTimingLog.traceEnd();// ShutdownActivityManagermetricEnded(METRIC_AM);Log.i(TAG, "Shutting down package manager...");shutdownTimingLog.traceBegin("ShutdownPackageManager");metricStarted(METRIC_PM);final PackageManagerService pm = (PackageManagerService) ServiceManager.getService("package");if (pm != null) {pm.shutdown();    // 关闭 PackageManagerService 服务}... ...    // 关闭一系列核心服务saveMetrics(mReboot, mReason);rebootOrShutdown(mContext, mReboot, mReason);    // 执行 rebootOrShutdown() 方法}}

3.5 ShutdownThread.rebootOrShutdown()

rebootOrShutdown() 方法决定 关机 还是 重启。

// frameworks/base/services/core/java/com/android/server/power/ShutdownThread.javapublic final class ShutdownThread extends Thread {public static void rebootOrShutdown(final Context context, boolean reboot, String reason) {if (reboot) {    // 判断是否重启Log.i(TAG, "Rebooting, reason: " + reason);PowerManagerService.lowLevelReboot(reason);Log.e(TAG, "Reboot failed, will attempt shutdown instead");reason = null;} else if (SHUTDOWN_VIBRATE_MS > 0 && context != null) {// vibrate before shutting downVibrator vibrator = new SystemVibrator(context);try {// 关机之前震动vibrator.vibrate(SHUTDOWN_VIBRATE_MS, VIBRATION_ATTRIBUTES);} catch (Exception e) {// Failure to vibrate shouldn't interrupt shutdown.  Just log it.Log.w(TAG, "Failed to vibrate during shutdown.", e);}// vibrator is asynchronous so we need to wait to avoid shutting down too soon.try {Thread.sleep(SHUTDOWN_VIBRATE_MS);} catch (InterruptedException unused) {}}// Shutdown powerLog.i(TAG, "Performing low-level shutdown...");PowerManagerService.lowLevelShutdown(reason);}}

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