Android恢复出厂设置流程分析【Android源码解析十】

最近看恢复出厂的一个问题，以前也查过这方面的流程，所以这里整理一些AP+framework层的流程；
在setting-->备份与重置--->恢复出厂设置--->重置手机--->清除全部内容--->手机关机--->开机--->进行恢复出厂的操作--->开机流程；

Step 1：前面找settings中的布局我就省略了，这部分相对简单一些，直接到清除全部内容这个按钮的操作，
对应的java类是setting中的MasterClearConfirm.java这个类，

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private Button.OnClickListener mFinalClickListener = new Button.OnClickListener() {

public void onClick(View v) {

if (Utils.isMonkeyRunning()) {

return;

}

if (mEraseSdCard) {

Intent intent = new Intent(ExternalStorageFormatter.FORMAT_AND_FACTORY_RESET);

intent.setComponent(ExternalStorageFormatter.COMPONENT_NAME);

getActivity().startService(intent);

} else {

getActivity().sendBroadcast(new Intent("android.intent.action.MASTER_CLEAR"));

// Intent handling is asynchronous -- assume it will happen soon.

}

}

};

通过上述的代码，可以看出，实际上点击清除全部内容的时候，如果前面勾选上格式哈SD卡，就会执行mEraseSdCard为true里面的逻辑，如果没有勾选，就执行mEraseSdCard=false的逻辑，其实就是发送一个广播，

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<span style="font-size:14px;">“android.intent.action.MASTER_CLEAR”</span>

Step 2：这个广播接受的地方，参见AndroidManifest.xml中的代码，如下：

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<receiver android:name="com.android.server.MasterClearReceiver"

android:permission="android.permission.MASTER_CLEAR"

android:priority="100" >

<intent-filter>

<!-- For Checkin, Settings, etc.: action=MASTER_CLEAR -->

<action android:name="android.intent.action.MASTER_CLEAR" />

<!-- MCS always uses REMOTE_INTENT: category=MASTER_CLEAR -->

<action android:name="com.google.android.c2dm.intent.RECEIVE" />

<category android:name="android.intent.category.MASTER_CLEAR" />

</intent-filter>

</receiver>

找这个MasterClearReceiver.java这个receiver，下面来看看这个onReceiver()里面做了什么操作：

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public void onReceive(final Context context, final Intent intent) {

if (intent.getAction().equals(Intent.ACTION_REMOTE_INTENT)) {

if (!"google.com".equals(intent.getStringExtra("from"))) {

Slog.w(TAG, "Ignoring master clear request -- not from trusted server.");

return;

}

}

Slog.w(TAG, "!!! FACTORY RESET !!!");

// The reboot call is blocking, so we need to do it on another thread.

Thread thr = new Thread("Reboot") {

@Override

public void run() {

try {

RecoverySystem.rebootWipeUserData(context);

Log.wtf(TAG, "Still running after master clear?!");

} catch (IOException e) {

Slog.e(TAG, "Can't perform master clear/factory reset", e);

}

}

};

thr.start();

}

这个里面主要的操作是：RecoverySystem.rebootWipeUserData(context);准备做重启的动作，告诉手机要清除userData的数据；

Step 3：接着来看看RecoverySystem.rebootWipeUserData（）这个方法做了哪些操作：

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public static void rebootWipeUserData(Context context) throws IOException {

final ConditionVariable condition = new ConditionVariable();

Intent intent = new Intent("android.intent.action.MASTER_CLEAR_NOTIFICATION");

context.sendOrderedBroadcastAsUser(intent, UserHandle.OWNER,

android.Manifest.permission.MASTER_CLEAR,

new BroadcastReceiver() {

@Override

public void onReceive(Context context, Intent intent) {

condition.open();

}

}, null, 0, null, null);

// Block until the ordered broadcast has completed.

condition.block();

bootCommand(context, "--wipe_data\n--locale=" + Locale.getDefault().toString());

}

这个里面的广播可以先忽略不计，重点来看看bootCommand（）这个方法，注意这个参数“--wipe_data\n--locale=”

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private static void bootCommand(Context context, String arg) throws IOException {

RECOVERY_DIR.mkdirs(); // In case we need it

COMMAND_FILE.delete(); // In case it's not writable

LOG_FILE.delete();

FileWriter command = new FileWriter(COMMAND_FILE);

try {

command.write(arg);

command.write("\n");

} finally {

command.close();

}

// Having written the command file, go ahead and reboot

PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);

pm.reboot("recovery");

throw new IOException("Reboot failed (no permissions?)");

}

这个方法的操作大致是“写节点/cache/recovery/command”，把传递过来的字符串写进去；然后调用PowerManager进行重启操作，reboot（）；

Step 4：接着我们来看看PowerManager的reboot方法做了哪些操作：

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public void reboot(String reason) {

try {

mService.reboot(false, reason, true);

} catch (RemoteException e) {

}

}

这个调用到了PowerManagerService.java这个类的reboot方法中了：

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@Override // Binder call

public void reboot(boolean confirm, String reason, boolean wait) {

mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);

final long ident = Binder.clearCallingIdentity();

try {

shutdownOrRebootInternal(false, confirm, reason, wait);

} finally {

Binder.restoreCallingIdentity(ident);

}

}

重点来看看shutdownOrRebootInternal（）这个方法，

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private void shutdownOrRebootInternal(final boolean shutdown, final boolean confirm,

final String reason, boolean wait) {

if (mHandler == null || !mSystemReady) {

throw new IllegalStateException("Too early to call shutdown() or reboot()");

}

Runnable runnable = new Runnable() {

@Override

public void run() {

synchronized (this) {

if (shutdown) {

ShutdownThread.shutdown(mContext, confirm);

} else {

ShutdownThread.reboot(mContext, reason, confirm);

}

}

}

};

// ShutdownThread must run on a looper capable of displaying the UI.

Message msg = Message.obtain(mHandler, runnable);

msg.setAsynchronous(true);

mHandler.sendMessage(msg);

// PowerManager.reboot() is documented not to return so just wait for the inevitable.

if (wait) {

synchronized (runnable) {

while (true) {

try {

runnable.wait();

} catch (InterruptedException e) {

}

}

}

}

}

由于传递过来的shutdown为false，所以执行ShutdownThread.reboot(mContext, reason, confirm);reason：recevory
下面调用到ShutdownThread

Step 5：这个追踪ShutdownThread.reboot()这个方法，这就有点像破案电影，一点一点查找罪犯的难点；
来窥视一下这个类：

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public static void reboot(final Context context, String reason, boolean confirm) {

mReboot = true;

mRebootSafeMode = false;

mRebootReason = reason;

Log.d(TAG, "reboot");

shutdownInner(context, confirm);

}

这个里面做的操作就是给这个变量mRebootReason复制“recevory”，重点调用shutdownInner（）这个方法；

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<span style="font-size:14px;">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;

}

}

Log.d(TAG, "Notifying thread to start radio shutdown");

bConfirmForAnimation = confirm;

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) {

final CloseDialogReceiver closer = new CloseDialogReceiver(context);

if (sConfirmDialog != null) {

sConfirmDialog.dismiss();

}

if (sConfirmDialog == null) {

Log.d(TAG, "PowerOff dialog doesn't exist. Create it first");

sConfirmDialog = 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);

if (sConfirmDialog != null) {

sConfirmDialog = null;

}

}

})

.setNegativeButton(com.android.internal.R.string.no, new DialogInterface.OnClickListener() {

public void onClick(DialogInterface dialog, int which) {

synchronized (sIsStartedGuard) {

sIsStarted = false;

}

if (sConfirmDialog != null) {

sConfirmDialog = null;

}

}

})

.create();

sConfirmDialog.setCancelable(false);//blocking back key

sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);

/*if (!context.getResources().getBoolean(

com.android.internal.R.bool.config_sf_slowBlur)) {

sConfirmDialog.getWindow().addFlags(WindowManager.LayoutParams.FLAG_BLUR_BEHIND);

}*/

/* To fix video+UI+blur flick issue */

sConfirmDialog.getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);

}

closer.dialog = sConfirmDialog;

sConfirmDialog.setOnDismissListener(closer);

if (!sConfirmDialog.isShowing()) {

sConfirmDialog.show();

}

} else {

beginShutdownSequence(context);

}

}</span>

看beginShutdownSequence（）这个方法吧，重点调用到这个方法里面去了，来瞅瞅这个方法：

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<span style="font-size:14px;">private static void beginShutdownSequence(Context context) {

synchronized (sIsStartedGuard) {

if (sIsStarted) {

Log.e(TAG, "ShutdownThread is already running, returning.");

return;

}

sIsStarted = true;

}

// start the thread that initiates shutdown

sInstance.mContext = context;

sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);

sInstance.mHandler = new Handler() {

};

bPlayaudio = true;

if (!bConfirmForAnimation) {

if (!sInstance.mPowerManager.isScreenOn()) {

bPlayaudio = false;

}

}

// throw up an indeterminate system dialog to indicate radio is

// shutting down.

beginAnimationTime = 0;

boolean mShutOffAnimation = false;

try {

if (mIBootAnim == null) {

mIBootAnim = MediatekClassFactory.createInstance(IBootAnimExt.class);

}

} catch (Exception e) {

e.printStackTrace();

}

int screenTurnOffTime = mIBootAnim.getScreenTurnOffTime();

mShutOffAnimation = mIBootAnim.isCustBootAnim();

Log.e(TAG, "mIBootAnim get screenTurnOffTime : " + screenTurnOffTime);

String cust = SystemProperties.get("ro.operator.optr");

if (cust != null) {

if (cust.equals("CUST")) {

mShutOffAnimation = true;

}

}

synchronized (mEnableAnimatingSync) {

if(!mEnableAnimating) {

// sInstance.mPowerManager.setBacklightBrightness(PowerManager.BRIGHTNESS_DIM);

} else {

if (mShutOffAnimation) {

Log.e(TAG, "mIBootAnim.isCustBootAnim() is true");

bootanimCust();

} else {

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);

/* To fix video+UI+blur flick issue */

pd.getWindow().addFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);

pd.show();

}

sInstance.mHandler.postDelayed(mDelayDim, screenTurnOffTime );

}

}

// make sure we never fall asleep again

sInstance.mCpuWakeLock = null;

try {

sInstance.mCpuWakeLock = sInstance.mPowerManager.newWakeLock(

。。。 。。。

}</span>

这段代码有句话会影响关机动画播放不完
“sInstance.mHandler.postDelayed(mDelayDim, screenTurnOffTime ); ”

解决办法
（1）“可以把这个screenTurnOffTime时间乘以2，这个时间看log是5000毫秒，就是5秒，乘以2就是10秒，大概就能播放完全关机动画了。”
（2）把这句话注释掉，但是有可能会引起问题，导致恢复出厂设置的时候没有进行恢复出厂的操作。目前正在追踪此问题；

这段代码中还有影响关机动画是否走客制化的关机动画，如果ro.operator.optr这个属性配置的是CUST，则会走客制化的关机动画，否则走系统默认的关机动画；

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String cust = SystemProperties.get("ro.operator.optr");

if (cust != null) {

if (cust.equals("CUST")) {

mShutOffAnimation = true;

}

}

然后重点看 sInstance.start();这个方法，就走到了run（）方法里满了；

Step 6： 来看看ShutDownThread.java这个类的run（）方法；

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<span style="font-size:14px;">public void run() {

checkShutdownFlow();

while (mShutdownFlow == IPO_SHUTDOWN_FLOW) {

stMgr.saveStates(mContext);

stMgr.enterShutdown(mContext);

running();

}

if (mShutdownFlow != IPO_SHUTDOWN_FLOW) {

stMgr.enterShutdown(mContext);

running();

}

}</span>

重点看running（）这个方法：
下面这个方法比较长，来分析一下：

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<span style="font-size:14px;">public void running() {

if(sPreShutdownApi != null){

try {

sPreShutdownApi.onPowerOff();

} catch (RemoteException e) {

Log.e(TAG, "onPowerOff exception" + e.getMessage());

}

}else{

Log.w(TAG, "sPreShutdownApi is null");

}

command = SystemProperties.get("sys.ipo.pwrdncap");

BroadcastReceiver br = new BroadcastReceiver() {

@Override public void onReceive(Context context, Intent intent) {

// We don't allow apps to cancel this, so ignore the result.

actionDone();

}

};

/*

* Write a system property in case the system_server reboots before we

* get to the actual hardware restart. If that happens, we'll retry at

* the beginning of the SystemServer startup.

*/

{

String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");

SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);

}

/*

* If we are rebooting into safe mode, write a system property

* indicating so.

*/

if (mRebootSafeMode) {

SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");

}

Log.i(TAG, "Sending shutdown broadcast...");

// First send the high-level shut down broadcast.

mActionDone = false;

/// M: 2012-05-20 ALPS00286063 @{

mContext.sendBroadcast(new Intent("android.intent.action.ACTION_PRE_SHUTDOWN"));

/// @} 2012-05-20

mContext.sendOrderedBroadcastAsUser((new Intent()).setAction(Intent.ACTION_SHUTDOWN).putExtra("_mode", mShutdownFlow),

UserHandle.ALL, null, br, mHandler, 0, null, null);

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 ACTION_SHUTDOWN timed out");

if (mShutdownFlow == IPO_SHUTDOWN_FLOW) {

Log.d(TAG, "change shutdown flow from ipo to normal: ACTION_SHUTDOWN timeout");

mShutdownFlow = NORMAL_SHUTDOWN_FLOW;

}

break;

}

try {

mActionDoneSync.wait(delay);

} catch (InterruptedException e) {

}

}

}

// Also send ACTION_SHUTDOWN_IPO in IPO shut down flow

if (mShutdownFlow == IPO_SHUTDOWN_FLOW) {

mActionDone = false;

mContext.sendOrderedBroadcast(new Intent("android.intent.action.ACTION_SHUTDOWN_IPO"), null,

br, mHandler, 0, null, null);

final long endTimeIPO = SystemClock.elapsedRealtime() + MAX_BROADCAST_TIME;

synchronized (mActionDoneSync) {

while (!mActionDone) {

long delay = endTimeIPO - SystemClock.elapsedRealtime();

if (delay <= 0) {

Log.w(TAG, "Shutdown broadcast ACTION_SHUTDOWN_IPO timed out");

if (mShutdownFlow == IPO_SHUTDOWN_FLOW) {

Log.d(TAG, "change shutdown flow from ipo to normal: ACTION_SHUTDOWN_IPO timeout");

mShutdownFlow = NORMAL_SHUTDOWN_FLOW;

}

break;

}

try {

mActionDoneSync.wait(delay);

} catch (InterruptedException e) {

}

}

}

}

if (mShutdownFlow != IPO_SHUTDOWN_FLOW) {

// power off auto test, don't modify

Log.i(TAG, "Shutting down activity manager...");

final IActivityManager am =

ActivityManagerNative.asInterface(ServiceManager.checkService("activity"));

if (am != null) {

try {

am.shutdown(MAX_BROADCAST_TIME);

} catch (RemoteException e) {

}

}

}

// power off auto test, don't modify

// Shutdown radios.

Log.i(TAG, "Shutting down radios...");

shutdownRadios(MAX_RADIO_WAIT_TIME);

// power off auto test, don't modify

Log.i(TAG, "Shutting down MountService...");

if ( (mShutdownFlow == IPO_SHUTDOWN_FLOW) && (command.equals("1")||command.equals("3")) ) {

Log.i(TAG, "bypass MountService!");

} else {

// 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");

if (statusCode < 0) {

mShutdownFlow = NORMAL_SHUTDOWN_FLOW;

}

actionDone();

}

};

// Set initial variables and time out time.

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");

if (mShutdownFlow == IPO_SHUTDOWN_FLOW) {

Log.d(TAG, "change shutdown flow from ipo to normal: MountService");

mShutdownFlow = NORMAL_SHUTDOWN_FLOW;

}

break;

}

try {

mActionDoneSync.wait(delay);

} catch (InterruptedException e) {

}

}

}

}

// power off auto test, don't modify

//mountSerivce ���

Log.i(TAG, "MountService shut done...");

// [MTK] fix shutdown animation timing issue

//==================================================================

try {

SystemProperties.set("service.shutanim.running","1");

Log.i(TAG, "set service.shutanim.running to 1");

} catch (Exception ex) {

Log.e(TAG, "Failed to set 'service.shutanim.running' = 1).");

}

//==================================================================

if (mShutdownFlow == IPO_SHUTDOWN_FLOW) {

if (SHUTDOWN_VIBRATE_MS > 0) {

// vibrate before shutting down

Vibrator vibrator = new SystemVibrator();

try {

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) {

}

}

// Shutdown power

// power off auto test, don't modify

Log.i(TAG, "Performing ipo low-level shutdown...");

delayForPlayAnimation();

if (sInstance.mScreenWakeLock != null && sInstance.mScreenWakeLock.isHeld()) {

sInstance.mScreenWakeLock.release();

sInstance.mScreenWakeLock = null;

}

sInstance.mHandler.removeCallbacks(mDelayDim);

stMgr.shutdown(mContext);

stMgr.finishShutdown(mContext);

//To void previous UI flick caused by shutdown animation stopping before BKL turning off

if (pd != null) {

pd.dismiss();

pd = null;

} else if (beginAnimationTime > 0) {

try {

SystemProperties.set("service.bootanim.exit","1");

Log.i(TAG, "set 'service.bootanim.exit' = 1).");

} catch (Exception ex) {

Log.e(TAG, "Failed to set 'service.bootanim.exit' = 1).");

}

//SystemProperties.set("ctl.stop","bootanim");

}

synchronized (sIsStartedGuard) {

sIsStarted = false;

}

sInstance.mPowerManager.setBacklightBrightnessOff(false);

sInstance.mCpuWakeLock.acquire(2000);

synchronized (mShutdownThreadSync) {

try {

mShutdownThreadSync.wait();

} catch (InterruptedException e) {

}

}

} else {

rebootOrShutdown(mReboot, mRebootReason);

}

}</span>

这个方法做了一些列的操作，会关闭一些操作，如：

shutdownRadios(MAX_RADIO_WAIT_TIME);
mount.shutdown(observer);
stMgr.shutdown(mContext);

重点看 rebootOrShutdown(mReboot, mRebootReason);这个方法；准备重启的方法；

Step 7：来看看rebootOrShutdown（）这个方法：

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<span style="font-size:14px;">public static void rebootOrShutdown(boolean reboot, String reason) {

if (reboot) {

Log.i(TAG, "Rebooting, reason: " + reason);

if ( (reason != null) && reason.equals("recovery") ) {

delayForPlayAnimation();

}

try {

PowerManagerService.lowLevelReboot(reason);

} catch (Exception e) {

Log.e(TAG, "Reboot failed, will attempt shutdown instead", e);

}

} else if (SHUTDOWN_VIBRATE_MS > 0) {

// vibrate before shutting down

Vibrator vibrator = new SystemVibrator();

try {

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) {

}

}

delayForPlayAnimation();

// Shutdown power

// power off auto test, don't modify

Log.i(TAG, "Performing low-level shutdown...");

//PowerManagerService.lowLevelShutdown();

//add your func: HDMI off

//add for MFR

try {

if (ImHDMI == null)

ImHDMI=MediatekClassFactory.createInstance(IHDMINative.class);

} catch (Exception e) {

e.printStackTrace();

}

ImHDMI.hdmiPowerEnable(false);

try {

if (mTvOut == null)

mTvOut =MediatekClassFactory.createInstance(ITVOUTNative.class);

} catch (Exception e) {

e.printStackTrace();

}

mTvOut.tvoutPowerEnable(false);

//add your func: HDMI off

//unmout data/cache partitions while performing shutdown

SystemProperties.set("ctl.start", "shutdown");

/* sleep for a long time, prevent start another service */

try {

Thread.currentThread().sleep(Integer.MAX_VALUE);

} catch ( Exception e) {

Log.e(TAG, "Shutdown rebootOrShutdown Thread.currentThread().sleep exception!");

}

}</span>

关机震动也在这个方法里面；这个方法重点看PowerManagerService.lowLevelReboot(reason);
Log.i(TAG, "Rebooting, reason: " + reason);这句log也很重要，可以有助于我们分析代码；

Step 8：下面来看看PowerManagerServices.java这个类的lowLevelReboot（）这个方法：

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<span style="font-size:18px;">public static void lowLevelReboot(String reason) throws IOException {

nativeReboot(reason);

}</span>

这个方法调用到了native里面，后面的操作我就不分析了。。。

大致流程是：
关机，然后开机，底层判断节点后进入恢复出厂模式，recevory.img释放完全后，进入开机的流程。。。
以后有进展再补充这部分的流程，整个过程大致就是这个样子了，里面的细节有好多没有分析，大家可以自行研究。。。，抛砖引玉的目的达到了。
http://blog.csdn.net/mirkerson/article/details/24322207