Android关机流程源码分析

上一篇文章Android 开关机动画显示源码分析详细介绍了开关机动画的显示过程，Android系统开机时，在启动SurfaceFlinger服务过程中通过Android属性系统方式来启动bootanim进程，实现开机动画显示过程；当系统关机时，又是如何启动关机动画的呢？Android系统的整个关机流程又是怎样的呢？本文就针对这两个问题透过源码来给出具体的分析。我们知道，当长按电源键，系统会弹出关机提示对话框

当点击选择关机时，系统就会完成整个关机流程。接下来就通过源码来介绍Android关机流程的完整实现过程。当长按电源键时，按键消息被分发到PhoneWindowManager的interceptKeyBeforeQueueing函数中处理：

public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags, boolean isScreenOn) {...switch (keyCode) {...case KeyEvent.KEYCODE_POWER: {result &= ~ACTION_PASS_TO_USER;if (down) {if (isScreenOn && !mPowerKeyTriggered&& (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {mPowerKeyTriggered = true;mPowerKeyTime = event.getDownTime();interceptScreenshotChord();//抓屏}ITelephony telephonyService = getTelephonyService();boolean hungUp = false;if (telephonyService != null) {try {if (telephonyService.isRinging()) {//当来电时按下电源键，启动静音telephonyService.silenceRinger();} else if ((mIncallPowerBehavior& Settings.Secure.INCALL_POWER_BUTTON_BEHAVIOR_HANGUP) != 0&& telephonyService.isOffhook()) {// Otherwise, if "Power button ends call" is enabled,// the Power button will hang up any current active call.hungUp = telephonyService.endCall();}} catch (RemoteException ex) {Log.w(TAG, "ITelephony threw RemoteException", ex);}}interceptPowerKeyDown(!isScreenOn || hungUp|| mVolumeDownKeyTriggered || mVolumeUpKeyTriggered);} else {...}break;}...}return result;}

电源键和音量键的组合可以实现特定功能，比如按下电源键和音量向下键，可实现抓屏，interceptKeyBeforeQueueing函数首先根据条件处理电源键按下的特定任务，然后调用interceptPowerKeyDown做进一步处理

private void interceptPowerKeyDown(boolean handled) {mPowerKeyHandled = handled;if (!handled) {//隔500ms处理电源按键事件mHandler.postDelayed(mPowerLongPress, ViewConfiguration.getGlobalActionKeyTimeout());}}

这里的mHandler是在初始化PhoneWindowManager对象时创建的

public void init(Context context, IWindowManager windowManager,WindowManagerFuncs windowManagerFuncs,LocalPowerManager powerManager) {...mHandler = new PolicyHandler();...}

将一个Runnable对象mPowerLongPress发送到PolicyHandler中进行处理

private final Runnable mPowerLongPress = new Runnable() {public void run() {// The context isn't readif (mLongPressOnPowerBehavior < 0) {mLongPressOnPowerBehavior = mContext.getResources().getInteger(com.android.internal.R.integer.config_longPressOnPowerBehavior);}switch (mLongPressOnPowerBehavior) {case LONG_PRESS_POWER_NOTHING:break;case LONG_PRESS_POWER_GLOBAL_ACTIONS:mPowerKeyHandled = true;performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);showGlobalActionsDialog();break;case LONG_PRESS_POWER_SHUT_OFF:mPowerKeyHandled = true;performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);mWindowManagerFuncs.shutdown();break;}}};

在处理电源长按事件时，根据mLongPressOnPowerBehavior完成不同的处理过程，mLongPressOnPowerBehavior的值是通过配置文件来设置的，在frameworks/base/core/res/values/config.xml中有以下一段配置：

通过读取配置文件取得config_longPressOnPowerBehavior配置的值为1，因此将显示关机对话框

case LONG_PRESS_POWER_GLOBAL_ACTIONS:mPowerKeyHandled = true;performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);//向ActivityManagerService请求关闭所有窗口sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);//显示关机对话框showGlobalActionsDialog();break;

关机对话框显示：

void showGlobalActionsDialog() {//创建GlobalActions对象if (mGlobalActions == null) {mGlobalActions = new GlobalActions(mContext, mWindowManagerFuncs);}final boolean keyguardShowing = keyguardIsShowingTq();//显示对话框mGlobalActions.showDialog(keyguardShowing, isDeviceProvisioned());if (keyguardShowing) {// 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.mKeyguardMediator.pokeWakelock();}}

通过GlobalActions的showDialog函数来显示对话框

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();//关机对话框显示}}

private void handleShow() {//创建对话框mDialog = createDialog();prepareDialog();//设置对话框属性mDialog.show();//显示对话框mDialog.getWindow().getDecorView().setSystemUiVisibility(View.STATUS_BAR_DISABLE_EXPAND);}

createDialog()函数用于创建一个即将显示的关机对话框，就是前面图片显示的对话框。

private AlertDialog createDialog() {//=========================创建对话框显示的列表项视图=====================================//每一个列表项被被抽象为Action对象，// Simple toggle style if there's no vibrator, otherwise use a tri-stateif (!mHasVibrator) {mSilentModeAction = new SilentModeToggleAction();} else {mSilentModeAction = new SilentModeTriStateAction(mContext, mAudioManager, mHandler);}//创建飞行模式切换ToggleAction对象mAirplaneModeOn = new ToggleAction(R.drawable.ic_lock_airplane_mode,R.drawable.ic_lock_airplane_mode_off,R.string.global_actions_toggle_airplane_mode,R.string.global_actions_airplane_mode_on_status,R.string.global_actions_airplane_mode_off_status) {void onToggle(boolean on) {if (mHasTelephony && Boolean.parseBoolean(SystemProperties.get(TelephonyProperties.PROPERTY_INECM_MODE))) {mIsWaitingForEcmExit = true;// Launch ECM exit dialogIntent ecmDialogIntent =new Intent(TelephonyIntents.ACTION_SHOW_NOTICE_ECM_BLOCK_OTHERS, null);ecmDialogIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);mContext.startActivity(ecmDialogIntent);} else {changeAirplaneModeSystemSetting(on);mHandler.removeMessages(EVENT_SERVICE_CHANGE_WAIT_TIMEOUT);mHandler.sendEmptyMessageDelayed(EVENT_SERVICE_CHANGE_WAIT_TIMEOUT,DELAY_AIRPLANE_SET_TIME);}}@Overrideprotected void changeStateFromPress(boolean buttonOn) {if (!mHasTelephony) return;// In ECM mode airplane state cannot be changedif (!(Boolean.parseBoolean(SystemProperties.get(TelephonyProperties.PROPERTY_INECM_MODE)))) {mState = buttonOn ? State.TurningOn : State.TurningOff;mAirplaneState = mState;}}public boolean showDuringKeyguard() {return true;}public boolean showBeforeProvisioning() {return false;}};//更新当前飞行模式状态onAirplaneModeChanged();onRadioBusyStateChanged();mItems = new ArrayList<Action>();//向mItems列表中依次添加关机选择，飞行模式切换，静音模式选择// first: power offmItems.add(//创建关机SinglePressActionnew SinglePressAction(com.android.internal.R.drawable.ic_lock_power_off,R.string.global_action_power_off) {public void onPress() {// shutdown by making sure radio and power are handled accordingly.mWindowManagerFuncs.shutdown();}public boolean onLongPress() {mWindowManagerFuncs.rebootSafeMode();return true;}public boolean showDuringKeyguard() {return true;}public boolean showBeforeProvisioning() {return true;}});// next: airplane modemItems.add(mAirplaneModeOn);// last: silent modeif (SHOW_SILENT_TOGGLE) {mItems.add(mSilentModeAction);}//获取系统中所有用户信息List<UserInfo> users = mContext.getPackageManager().getUsers();if (users.size() > 1) {//对于多用户Android系统，在显示的对话框下面添加用户切换选项UserInfo currentUser;try {currentUser = ActivityManagerNative.getDefault().getCurrentUser();} catch (RemoteException re) {currentUser = null;}for (final UserInfo user : users) {boolean isCurrentUser = currentUser == null? user.id == 0 : (currentUser.id == user.id);SinglePressAction switchToUser = new SinglePressAction(com.android.internal.R.drawable.ic_menu_cc,(user.name != null ? user.name : "Primary")+ (isCurrentUser ? " \u2714" : "")) {public void onPress() {try {ActivityManagerNative.getDefault().switchUser(user.id);getWindowManager().lockNow();} catch (RemoteException re) {Log.e(TAG, "Couldn't switch user " + re);}}public boolean showDuringKeyguard() {return true;}public boolean showBeforeProvisioning() {return false;}};mItems.add(switchToUser);}}mAdapter = new MyAdapter();//创建适配器，保存了所有数据，这里用MyAdapter保存列表项视图//=========================创建对话框=========================================final AlertDialog.Builder ab = new AlertDialog.Builder(mContext);ab.setAdapter(mAdapter, this).setInverseBackgroundForced(true);final AlertDialog dialog = ab.create();dialog.getListView().setItemsCanFocus(true);dialog.getListView().setLongClickable(true);dialog.getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {@Overridepublic boolean onItemLongClick(AdapterView<?> parent, View view, int position,long id) {return mAdapter.getItem(position).onLongPress();//视图和数据相关联}});dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_DIALOG);dialog.setOnDismissListener(this);return dialog;}

这里需要介绍对话框列表创建的方法，代码实现比较灵魂，值得学习。首先将显示对话框列表中的每一项用应该Action来描述，Action是一个接口，定义了每一个列表项的动作方法

各个列表项定义不同类型的Action，比如关机选项使用SinglePressAction来描述，目前Android系统定义了几种类型的Action，对应关机对话框中的不同选项。

将创建的列表选项添加到动态数组mItems中，并且为该对话框定义一个适配器MyAdapter，在单击对话框列表项时，调用适配器中对应的项来响应单击事件。Android适配器的使用实现了MVC编程模式，将数据和视图分开。通常我们将数据保存在一个数组中，通过适配器和视图控件关联显示，只不过这里的数据比较特殊，它是用来描述列表项显示的内容。

public boolean onItemLongClick(AdapterView<?> parent, View view, int position,long id) {return mAdapter.getItem(position).onLongPress();}public void onClick(DialogInterface dialog, int which) {if (!(mAdapter.getItem(which) instanceof SilentModeTriStateAction)) {dialog.dismiss();}mAdapter.getItem(which).onPress();}

对于关机选项，其单击和长按事件处理过程如下：

public void onPress() {// shutdown by making sure radio and power are handled accordingly.mWindowManagerFuncs.shutdown();}public boolean onLongPress() {mWindowManagerFuncs.rebootSafeMode();return true;}

对关机的处理都是调用mWindowManagerFuncs来完成的，mWindowManagerFuncs的类型为WindowManagerFuncs，在调用PhoneWindowManager的init函数时通过参数传进来。mWindowManagerFuncs对象在那里构造呢？WindowManagerService定义了一个WindowManagerPolicy类型变量：

final WindowManagerPolicy mPolicy = PolicyManager.makeNewWindowManager();

通过策略管理类PolicyManager对象的makeNewWindowManager函数创建一个窗口策略管理对象

public static WindowManagerPolicy makeNewWindowManager() {return sPolicy.makeNewWindowManager();}

该函数通过Binder通信方式请求服务端Policy来完成对象的创建过程

Policy.java

public WindowManagerPolicy makeNewWindowManager() {return new PhoneWindowManager();}

在WindowManagerService的构造过程中，会创建一个PolicyThread类来初始化窗口管理策略WindowManagerPolicy

private WindowManagerService(Context context, PowerManagerService pm,boolean haveInputMethods, boolean showBootMsgs, boolean onlyCore) {...PolicyThread thr = new PolicyThread(mPolicy, this, context, pm);thr.start();synchronized (thr) {while (!thr.mRunning) {try {thr.wait();} catch (InterruptedException e) {}}}...}

在PolicyThread线程中执行初始化函数

static class PolicyThread extends Thread {@Overridepublic void run() {Looper.prepare();...mPolicy.init(mContext, mService, mService, mPM);synchronized (this) {mRunning = true;notifyAll();}...Looper.loop();}}

mPolicy的类型定义为WindowManagerPolicy类型，而WindowManagerPolicy是一个接口类型，PhoneWindowManager实现了该接口，为mPolicy创建的真正对象是PhoneWindowManager对象，因此PolicyThread线程将调用PhoneWindowManager的init函数

public void init(Context context, IWindowManager windowManager,WindowManagerFuncs windowManagerFuncs,LocalPowerManager powerManager) {...mWindowManagerFuncs = windowManagerFuncs;...}

传进来的参数windowManager和windowManagerFuncs都是WindowManagerService对象，因为WindowManagerService继承于IWindowManager.Stub类同时实现了WindowManagerPolicy.WindowManagerFuncs接口，这下就很清晰地知道GlobalActions类中的mWindowManagerFuncs变量其实是WindowManagerService对象，因此关机的单击及长按事件由WindowManagerService实现：

public void shutdown() {ShutdownThread.shutdown(mContext, true);}public void rebootSafeMode() {ShutdownThread.rebootSafeMode(mContext, true);}

WindowManagerService也不真正实现关机操作，而是转交个ShutdownThread来完成。对于关机处理过程：

public static void shutdown(final Context context, boolean confirm) {mReboot = false;mRebootSafeMode = false;shutdownInner(context, confirm);}

该函数实现非常简单，只是设置一些标志位，然后将关机任务又转交给shutdownInner来处理，这里的参数confirm用于标识是否需要弹出关机确认对话框。

static void shutdownInner(final Context context, boolean confirm) {// ensure that only one thread is trying to power down.// any additional calls are just returnedsynchronized (sIsStartedGuard) {if (sIsStarted) {Log.d(TAG, "Request to shutdown already running, returning.");return;}}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);//显示关机确认对话框if (confirm) {final CloseDialogReceiver closer = new CloseDialogReceiver(context);final AlertDialog dialog = 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);}}).setNegativeButton(com.android.internal.R.string.no, null).create();closer.dialog = dialog;dialog.setOnDismissListener(closer);dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);dialog.show();} else {//不显示关机确认对话框，直接进入关机流程beginShutdownSequence(context);}}

调用beginShutdownSequence函数进入关机流程。

private static void beginShutdownSequence(Context context) {synchronized (sIsStartedGuard) {if (sIsStarted) {Log.d(TAG, "Shutdown sequence already running, returning.");return;}sIsStarted = true;}// throw up an indeterminate system dialog to indicate radio is// shutting down.ProgressDialog pd = new ProgressDialog(context);pd.setTitle(context.getText(com.android.internal.R.string.power_off));pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress));pd.setIndeterminate(true);pd.setCancelable(false);pd.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);//pd.show();shutdownTime = SystemClock.elapsedRealtime() + MAX_SHUTDOWN_TIME;//执行关机动画String[] bootcmd = {"bootanimation", "shutdown"} ;try {Log.i(TAG, "exec the bootanimation ");SystemProperties.set("service.bootanim.exit", "0");Runtime.getRuntime().exec(bootcmd);} catch (Exception e){    Log.e(TAG,"bootanimation command exe err!");} //初始化关机线程ShutdownThreadsInstance.mContext = context;sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);// make sure we never fall asleep againsInstance.mCpuWakeLock = null;try {sInstance.mCpuWakeLock = sInstance.mPowerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG + "-cpu");sInstance.mCpuWakeLock.setReferenceCounted(false);sInstance.mCpuWakeLock.acquire();} catch (SecurityException e) {Log.w(TAG, "No permission to acquire wake lock", e);sInstance.mCpuWakeLock = null;}// also make sure the screen stays on for better user experiencesInstance.mScreenWakeLock = null;if (sInstance.mPowerManager.isScreenOn()) {try {sInstance.mScreenWakeLock = sInstance.mPowerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK, TAG + "-screen");sInstance.mScreenWakeLock.setReferenceCounted(false);sInstance.mScreenWakeLock.acquire();} catch (SecurityException e) {Log.w(TAG, "No permission to acquire wake lock", e);sInstance.mScreenWakeLock = null;}}// start the thread that initiates shutdownsInstance.mHandler = new Handler() {};//启动关机线程ShutdownThreadsInstance.start();}

这个函数执行两个任务，1）通过虚拟机Runtime启动关机动画进程bootanimation，用于显示关机动画，开关机动画在Android 开关机动画显示源码分析进行了详细的分析介绍。2）启动关机线程ShutdownThread来完成关机操作

public void run() {BroadcastReceiver br = new BroadcastReceiver() {@Override public void onReceive(Context context, Intent intent) {// 用于接收关机广播actionDone();}};//写属性"sys.shutdown.requested"保存关机原因{String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);}//如果是安全模式关机，写属性"persist.sys.safemode"if (mRebootSafeMode) {SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");}Log.i(TAG, "Sending shutdown broadcast...");// First send the high-level shut down broadcast.mActionDone = false;//发送关机广播mContext.sendOrderedBroadcast(new Intent(Intent.ACTION_SHUTDOWN), null,br, mHandler, 0, null, null);//等待10S，前面定义的广播接收器收到关机广播时mActionDone设置为true，同时取消等待final long endTime = SystemClock.elapsedRealtime() + MAX_BROADCAST_TIME;synchronized (mActionDoneSync) {while (!mActionDone) {long delay = endTime - SystemClock.elapsedRealtime();if (delay <= 0) {Log.w(TAG, "Shutdown broadcast timed out");break;}try {mActionDoneSync.wait(delay);} catch (InterruptedException e) {}}}//10S时间内关闭ActivityManager服务final IActivityManager am =ActivityManagerNative.asInterface(ServiceManager.checkService("activity"));if (am != null) {try {am.shutdown(MAX_BROADCAST_TIME);} catch (RemoteException e) {}}//12s内关闭radios.shutdownRadios(MAX_RADIO_WAIT_TIME);//10s内关闭ICCSshutdownIccs(MAX_ICC_WAIT_TIME);// Shutdown MountService to ensure media is in a safe stateIMountShutdownObserver observer = new IMountShutdownObserver.Stub() {public void onShutDownComplete(int statusCode) throws RemoteException {Log.w(TAG, "Result code " + statusCode + " from MountService.shutdown");actionDone();}};Log.i(TAG, "Shutting down MountService");//20s内关闭MountService服务mActionDone = false;final long endShutTime = SystemClock.elapsedRealtime() + MAX_SHUTDOWN_WAIT_TIME;synchronized (mActionDoneSync) {try {final IMountService mount = IMountService.Stub.asInterface(ServiceManager.checkService("mount"));if (mount != null) {mount.shutdown(observer);} else {Log.w(TAG, "MountService unavailable for shutdown");}} catch (Exception e) {Log.e(TAG, "Exception during MountService shutdown", e);}while (!mActionDone) {long delay = endShutTime - SystemClock.elapsedRealtime();if (delay <= 0) {Log.w(TAG, "Shutdown wait timed out");break;}try {mActionDoneSync.wait(delay);} catch (InterruptedException e) {}}}//关机时间定义为5s，这里计算关机超过的时间long shutdownDelay = shutdownTime - SystemClock.elapsedRealtime();if (shutdownDelay > 0) {Log.i(TAG, "Shutdown delay:"+shutdownDelay);SystemClock.sleep(shutdownDelay);}//继续关机rebootOrShutdown(mReboot, mRebootReason);}

该函数内主要完成以下一些工作：

(1)发送关机广播ACTION_SHUTDOWN

(2)关闭ActivityManager 服务

(3)关闭无线相关的服务

(4)关闭Iccs

(5)关闭MountService服务

public static void rebootOrShutdown(boolean reboot, String reason) {if (reboot) {//是否重启Log.i(TAG, "Rebooting, reason: " + reason);try {PowerManagerService.lowLevelReboot(reason);} catch (Exception e) {Log.e(TAG, "Reboot failed, will attempt shutdown instead", e);}} else if (SHUTDOWN_VIBRATE_MS > 0) {//震动时间为500ms// vibrate before shutting downVibrator vibrator = new SystemVibrator();try {//关机震动500msvibrator.vibrate(SHUTDOWN_VIBRATE_MS);} 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) {}}//关闭电源Log.i(TAG, "Performing low-level shutdown...");PowerManagerService.lowLevelShutdown();}

这里是启动关机震动并关闭电源

public static void lowLevelShutdown() {nativeShutdown();}

这里通过JNI调用C++的关机函数

static void nativeShutdown(JNIEnv *env, jobject clazz) {    delFlag();    android_reboot(ANDROID_RB_POWEROFF, 0, 0);}

android_reboot函数最终通过Linux系统调用关闭系统。到此关机操作就基本完成了。