Android Framework层Power键关机流程（二，关机流程）

二，关机流程

从前一篇博文我们知道，当用户长按Power键时会弹出（关机、重启，飞行模式等选项）对话框，我们点击关机，则会弹出关机确认对话框。那么从选项对话框到关机确认对话框又是一个什么流程呢。下面我们在简单分析一下：

showGlobalActionsDialog()-->showDialog()-->[b]handleShow()-->[/b]createDialog()-->onPress()-->shutdown()

PhoneWindowManager.java

void showGlobalActionsDialog() {

......

mGlobalActions.showDialog(keyguardShowing, isDeviceProvisioned());

......

}

GlobalActions.java

public void showDialog(boolean keyguardShowing, boolean isDeviceProvisioned) {

......

handleShow();

......

}

private void handleShow() {

......

mDialog = createDialog();

......

}

private GlobalActionsDialog createDialog(){

......

mItems = new ArrayList<Action>();

// first: power off

mItems.add(

new SinglePressAction(

com.android.internal.R.drawable.uirom_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(true);

}

public boolean onLongPress() {

mWindowManagerFuncs.rebootSafeMode(true);

return true;

}

public boolean showDuringKeyguard() {

return true;

}

public boolean showBeforeProvisioning() {

return true;

}

});

......

}

上述代码中的mWindowManagerFuncs实际上是WindowManagerService的对象，该对象有PhoneWindowManager的init的方法传入GlobalActions的构造函数中，并在上述代码中进行调用。下面这一行代码是调用的关键代码。

mPolicy.init(mContext, WindowManagerService.this, WindowManagerService.this);

下面是弹出“关机确认对话框”的堆栈：

01-16 18:08:21.497 D/bill ( 720): java.lang.Throwable

01-16 18:08:21.497 D/bill ( 720): at com.android.server.power.ShutdownThread.shutdown(ShutdownThread.java:175)

01-16 18:08:21.497 D/bill ( 720): at com.android.server.wm.WindowManagerService.shutdown(WindowManagerService.java:5783)01-16 18:08:21.497 D/bill ( 720):at com.android.internal.policy.impl.GlobalActions$2.onPress(GlobalActions.java:352)//WindowManagerService实现了接口WindowsManagerFuncs

01-16 18:08:21.497 D/bill ( 720): at com.android.internal.policy.impl.GlobalActions.onClick(GlobalActions.java:581)

01-16 18:08:21.497 D/bill ( 720): at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:952)

01-16 18:08:21.497 D/bill ( 720): at android.widget.AdapterView.performItemClick(AdapterView.java:299)

01-16 18:08:21.497 D/bill ( 720): at android.widget.AbsListView.performItemClick(AbsListView.java:1152)

01-16 18:08:21.497 D/bill ( 720): at android.widget.AbsListView$PerformClick.run(AbsListView.java:3014)

01-16 18:08:21.497 D/bill ( 720): at android.widget.AbsListView$3.run(AbsListView.java:3865)

01-16 18:08:21.497 D/bill ( 720): at android.os.Handler.handleCallback(Handler.java:808)

01-16 18:08:21.497 D/bill ( 720): at android.os.Handler.dispatchMessage(Handler.java:103)

01-16 18:08:21.497 D/bill ( 720): at android.os.Looper.loop(Looper.java:193)

01-16 18:08:21.497 D/bill ( 720): at android.os.HandlerThread.run(HandlerThread.java:61)

从这里（shutdown()）我们正式进入关机流程的关键。

shutdown()<ShutdownThread.java> --->shutdownInner() --->beginShutdownSequence（）--->run()--->rebootOrShutdown()--->lowLevelShutdown()<[b]PowerManagerService.java>--->[/b]

源码来自：https://github.com/android/platform_frameworks_base/blob/master/services/java/com/android/server/power/ShutdownThread.java

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

注！

参数2：confir;关机操作前是否需要用户进行确认

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);

//longPressBehavior的值标示当前长按Power操作意向（关机、重启。。。）

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();

}

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);

}

})

.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);

}

}

注：上述代码中，如果需要用户确认关机操作，则会弹出对话框，在对话框的确认按钮被触发时，调用beginShutdownSequence（）方法继续关机流程。如果无需用户确认，则直接调用beginShutdownSequence（）进入下一个关机流程节点。

在beginShutdownSequence（）有些手机厂商常常会在这里添加一些定制功能，例如在对话框中添加“下次快速开机”，定制关机动画等等。随后会根据不同平台进行讲解。下面这张图是Android原生系统的关机画面（对应下面加粗显示的代码）：



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();

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");[b]①

sInstance.mCpuWakeLock.setReferenceCounted(false);②

sInstance.mCpuWakeLock.acquire(); ③[/b]

} 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;④

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() {

};

sInstance.start();⑤

}

注解！

①上述红色代码中的作用主要是为了防止手机进入休眠状态，从代码中我们看到，此时通过PowerManager的newWakeLock方法生成了PowerManager.WakeLock对象。newWakeLock（）是PowerManager中最为常用的方法，该对象是一种锁机制，通过该对象可以控制设备的电源状态。在生成WakeLock实例时通过第一个参数的传入只开控制获取不同的WakeLock，主要是不同的lock对CPU，屏幕，键盘灯有不同的影响。如下：

PARTIAL_WAKE_LOCK:保持CPU 运转，屏幕和键盘灯有可能是关闭的。
SCREEN_DIM_WAKE_LOCK：保持CPU 运转，允许保持屏幕显示但有可能是灰的，允许关闭键盘灯
SCREEN_BRIGHT_WAKE_LOCK：保持CPU 运转，允许保持屏幕高亮显示，允许关闭键盘灯
FULL_WAKE_LOCK：保持CPU 运转，保持屏幕高亮显示，键盘灯也保持亮度

②Wake Lock 是一种锁的机制，只要有人拿着这个锁，系统九五案发进入休眠，可以被用户动态程序和内核获得，这个锁可以使有超时的或者是没有超时的，超时的锁会在时间过去以后自动解锁。如果没有锁了，或者超时了，内核就会启动休眠的那套机制来进入休眠。PowerManager.WakeLock有加锁和解锁的两种状态，加锁的方式有两种，一种是永久的锁住，这样的锁除非是显示的放开，否则是不会解锁的，所以这种锁用起来要非常小心，第二种锁是超时锁，这种锁会在锁住一段时间后自动解锁。
sInstance.mCpuWakeLock.setReferenceCounted(false);是设置锁的方式为永久的锁住。

③sInstance.mCpuWakeLock.acquire(); 加锁

④上述蓝色代码的作用是为了保证用户体验，保持屏幕、键盘的亮度

⑤接着启动关机线程，进入关机流程的下一个节点。

/**

* Makes sure we handle the shutdown gracefully.

* Shuts off power regardless of radio and bluetooth state if the alloted time has passed.

*/

public void run() {

BroadcastReceiver br = new BroadcastReceiver() {

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

actionDone();//这里用于接受关机广播，actionDone（）方法主要是防止应用程序取消关机操作。

}

};

/*

* 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;

Intent intent = new Intent(Intent.ACTION_SHUTDOWN);

intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);

mContext.sendOrderedBroadcastAsUser(intent,

UserHandle.ALL, null, br, mHandler, 0, null, null);//发送关机广播

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) {

}

}

}

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

final IActivityManager am =

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

if (am != null) {

try {

am.shutdown(MAX_BROADCAST_TIME);//关闭ActivityManagerService

} catch (RemoteException e) {

}

}

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

final PackageManagerService pm = (PackageManagerService)

ServiceManager.getService("package");

if (pm != null) {

pm.shutdown();//关闭PackageManagerService服务

}

// 关闭Radios

shutdownRadios(MAX_RADIO_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");

// 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);//关闭MountService

} 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) {

}

}

}

rebootOrShutdown(mReboot, mRebootReason);

}

最后调用rebootOrShutdown（）

public static void rebootOrShutdown(boolean reboot, String reason) {

if (reboot) {

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

PowerManagerService.lowLevelReboot(reason);

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

} else if (SHUTDOWN_VIBRATE_MS > 0) {

// vibrate before shutting down

Vibrator vibrator = new SystemVibrator();

try {

vibrator.vibrate(SHUTDOWN_VIBRATE_MS);//关机震动

} 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

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

PowerManagerService.lowLevelShutdown();//关闭电源

}

}

/**

* Low-level function turn the device off immediately, without trying

* to be clean. Most people should use {@link ShutdownThread} for a clean shutdown.

*/

public static void lowLevelShutdown() {

SystemProperties.set("sys.powerctl", "shutdown");//这里通过修改Android属性进行关机

}

注：上述代码中，红色加粗部分为关机关键代码，我也可以通过adb 命令进行修改Android系统的属性进行关机，具体命令如下

adb shell setprop sys.powerctl shutdown