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 read
if (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 completes
mHandler.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-state
if (!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 dialog
Intent 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);
}
}
@Override
protected void changeStateFromPress(boolean buttonOn) {
if (!mHasTelephony) return;
// In ECM mode airplane state cannot be changed
if (!(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 off
mItems.add(
//创建关机SinglePressAction
new 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 mode
mItems.add(mAirplaneModeOn);
// last: silent mode
if (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() {
@Override
public 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 {
@Override
public 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 returned
synchronized (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ShutdownThread
sInstance.mContext = context;
sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
// make sure we never fall asleep again
sInstance.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 experience
sInstance.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 shutdown
sInstance.mHandler = new Handler() {
};
//启动关机线程ShutdownThread
sInstance.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ICCS
shutdownIccs(MAX_ICC_WAIT_TIME);
// Shutdown MountService to ensure media is in a safe state
IMountShutdownObserver 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 down
Vibrator vibrator = new SystemVibrator();
try {
//关机震动500ms
vibrator.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。
