引言
在Android的开发中，相比较于关机流程，用户和开发者往往更加关注于开机性能和时间。
关机在普通用户的眼中，就是断电一下，并不需要太多的操作和流程。
但是实际不然，我们在关机过程中，怎么样有序的保存数据，记录状态，安全关机。
这个过程其实还是有很多的流程和环节需要注意。
那么本文，将会详细的梳理一下Android手机的关机流程。
流程实现
在Android系统中，如果对Framework比较熟悉，肯定知道控制开关机的核心的类为：
frameworks/base/services/core/java/com/android/server/power/ShutdownThread.java
在这个类中，我们可以看到构造方法为空构造方法：
private ShutdownThread() {
}这样会让其他模块如何调用呢？我们来看几个例子：
举例一：frameworks/base/services/core/java/com/android/server/statusbar/StatusBarManagerService.java
/**
* Allows the status bar to shutdown the device.
*/
@Override
public void shutdown() {
enforceStatusBarService();
long identity = Binder.clearCallingIdentity();
try {
mNotificationDelegate.prepareForPossibleShutdown();
// ShutdownThread displays UI, so give it a UI context.
mHandler.post(() ->
ShutdownThread.shutdown(getUiContext(),
PowerManager.SHUTDOWN_USER_REQUESTED, false));
} finally {
Binder.restoreCallingIdentity(identity);
}
}我们可以看到执行的是：ShutdownThread.shutdown(getUiContext(), PowerManager.SHUTDOWN_USER_REQUESTED, false));
举例二：frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java
Runnable runnable = new Runnable() {
@Override
public void run() {
synchronized (this) {
if (haltMode == HALT_MODE_REBOOT_SAFE_MODE) {
ShutdownThread.rebootSafeMode(getUiContext(), confirm);
} else if (haltMode == HALT_MODE_REBOOT) {
ShutdownThread.reboot(getUiContext(), reason, confirm);
} else {
ShutdownThread.shutdown(getUiContext(), reason, confirm);
}
}
}
};这边我们引用的是：ShutdownThread.shutdown(getUiContext(), reason, confirm);
举例三：frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
// Called by window manager policy. Not exposed externally.
@Override
public void shutdown(boolean confirm) {
// Pass in the UI context, since ShutdownThread requires it (to show UI).
ShutdownThread.shutdown(ActivityThread.currentActivityThread().getSystemUiContext(),
PowerManager.SHUTDOWN_USER_REQUESTED, confirm);
}这边调用的也是shutdown的方法：ShutdownThread.shutdown(ActivityThread.currentActivityThread().getSystemUiContext(), PowerManager.SHUTDOWN_USER_REQUESTED, confirm);
ShutDown方法实现
从刚才的例子中，我们可以看到，都是会通过无参的构造函数，去调用到shutdown的方法。
那么shutdown方法的实现如下：
/**
* Request a clean shutdown, waiting for subsystems to clean up their
* state etc. Must be called from a Looper thread in which its UI
* is shown.
*
* @param context Context used to display the shutdown progress dialog. This must be a context
* suitable for displaying UI (aka Themable).
* @param reason code to pass to android_reboot() (e.g. "userrequested"), or null.
* @param confirm true if user confirmation is needed before shutting down.
*/
public static void shutdown(final Context context, String reason, boolean confirm) {
mReboot = false;
mRebootSafeMode = false;
mReason = reason;
shutdownInner(context, confirm);
}可以看到除了对mReboot，mReason，mRebootSafeMode方法赋值以外，调用的就是shutdownInner的方法。
private static void shutdownInner(final Context context, boolean confirm) {
// ShutdownThread is called from many places, so best to verify here that the context passed
// in is themed.
context.assertRuntimeOverlayThemable();
// 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);
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(, null)
.create();
closer.dialog = sConfirmDialog;
sConfirmDialog.setOnDismissListener(closer);
sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);
sConfirmDialog.show();
} else {
beginShutdownSequence(context);
}
}这里的逻辑很简单，主要分为如下几个步骤：
// 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;
}
}系统只允许一个关机流程的线程去操作关机，所以当发现如果有多个的时候，将会终止后续的操作。
final CloseDialogReceiver closer = new CloseDialogReceiver(context);会去注册一个关机的Receiver，来接收相关的信息。
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(, null)
.create();
closer.dialog = sConfirmDialog;
sConfirmDialog.setOnDismissListener(closer);
sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);
sConfirmDialog.show();会去显示Dialog，并且会去执行beginShutdownSequence这个核心函数。
beginShutdownSequence函数实现
我们先来看一下beginShutdownSequence的函数实现：
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);
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;
}
}
if (SecurityLog.isLoggingEnabled()) {
SecurityLog.writeEvent(SecurityLog.TAG_OS_SHUTDOWN);
}
// start the thread that initiates shutdown
sInstance.mHandler = new Handler() {
};
sInstance.start();
}这里面，也是主要是两个操作：showShutdownDialog与start the thread that initiates shutdown.
首先看showShutdownDialog：
private static ProgressDialog showShutdownDialog(Context context) {
// Throw up a system dialog to indicate the device is rebooting / shutting down.
ProgressDialog pd = new ProgressDialog(context);
// Path 1: Reboot to recovery for update
// Condition: mReason startswith REBOOT_RECOVERY_UPDATE
//
// Path 1a: uncrypt needed
// Condition: if /cache/recovery/uncrypt_file exists but
// /cache/recovery/block.map doesn't.
// UI: determinate progress bar (mRebootHasProgressBar == True)
//
// * Path 1a is expected to be removed once the GmsCore shipped on
// device always calls uncrypt prior to reboot.
//
// Path 1b: uncrypt already done
// UI: spinning circle only (no progress bar)
//
// Path 2: Reboot to recovery for factory reset
// Condition: mReason == REBOOT_RECOVERY
// UI: spinning circle only (no progress bar)
//
// Path 3: Regular reboot / shutdown
// Condition: Otherwise
// UI: spinning circle only (no progress bar)
// mReason could be "recovery-update" or "recovery-update,quiescent".
if (mReason != null && mReason.startsWith(PowerManager.REBOOT_RECOVERY_UPDATE)) {
// We need the progress bar if uncrypt will be invoked during the
// reboot, which might be time-consuming.
mRebootHasProgressBar = RecoverySystem.UNCRYPT_PACKAGE_FILE.exists()
&& !(RecoverySystem.BLOCK_MAP_FILE.exists());
pd.setTitle(context.getText(com.android.internal.R.string.reboot_to_update_title));
if (mRebootHasProgressBar) {
pd.setMax(100);
pd.setProgress(0);
pd.setIndeterminate(false);
pd.setProgressNumberFormat(null);
pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pd.setMessage(context.getText(
com.android.internal.R.string.reboot_to_update_prepare));
} else {
if (showSysuiReboot()) {
return null;
}
pd.setIndeterminate(true);
pd.setMessage(context.getText(
com.android.internal.R.string.reboot_to_update_reboot));
}
} else if (mReason != null && mReason.equals(PowerManager.REBOOT_RECOVERY)) {
if (showSysuiReboot()) {
return null;
} else if (RescueParty.isAttemptingFactoryReset()) {
// We're not actually doing a factory reset yet; we're rebooting
// to ask the user if they'd like to reset, so give them a less
// scary dialog message.
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);
} else {
// Factory reset path. Set the dialog message accordingly.
pd.setTitle(context.getText(com.android.internal.R.string.reboot_to_reset_title));
pd.setMessage(context.getText(
com.android.internal.R.string.reboot_to_reset_message));
pd.setIndeterminate(true);
}
} else {
if (showSysuiReboot()) {
return null;
}
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();
return pd;
}这里主要是显示关机的进度的动画的实现。
关键的点还是start the thread that initiates shutdown.
首先看一下Instance的定义：
// static instance of this thread
private static final ShutdownThread sInstance = new ShutdownThread();那么，
sInstance.start();就会调用ShutDownThread的Run方法，去进行实现。
/**
* Makes sure we handle the shutdown gracefully.
* Shuts off power regardless of radio state if the allotted time has passed.
*/
public void run() {
TimingsTraceLog shutdownTimingLog = newTimingsLog();
shutdownTimingLog.traceBegin("SystemServerShutdown");
metricShutdownStart();
metricStarted(METRIC_SYSTEM_SERVER);
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") + (mReason != null ? mReason : "");
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");
}
shutdownTimingLog.traceBegin("DumpPreRebootInfo");
try {
Slog.i(TAG, "Logging pre-reboot information...");
PreRebootLogger.log(mContext);
} catch (Exception e) {
Slog.e(TAG, "Failed to log pre-reboot information", e);
}
shutdownTimingLog.traceEnd(); // DumpPreRebootInfo
metricStarted(METRIC_SEND_BROADCAST);
shutdownTimingLog.traceBegin("SendShutdownBroadcast");
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 | Intent.FLAG_RECEIVER_REGISTERED_ONLY);
mContext.sendOrderedBroadcastAsUser(intent,
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 timed out");
break;
} else if (mRebootHasProgressBar) {
int status = (int)((MAX_BROADCAST_TIME - delay) * 1.0 *
BROADCAST_STOP_PERCENT / MAX_BROADCAST_TIME);
sInstance.setRebootProgress(status, null);
}
try {
mActionDoneSync.wait(Math.min(delay, ACTION_DONE_POLL_WAIT_MS));
} catch (InterruptedException e) {
}
}
}
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(BROADCAST_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd(); // SendShutdownBroadcast
metricEnded(METRIC_SEND_BROADCAST);
Log.i(TAG, "Shutting down activity manager...");
shutdownTimingLog.traceBegin("ShutdownActivityManager");
metricStarted(METRIC_AM);
final IActivityManager am =
IActivityManager.Stub.asInterface(ServiceManager.checkService("activity"));
if (am != null) {
try {
am.shutdown(MAX_BROADCAST_TIME);
} catch (RemoteException e) {
}
}
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(ACTIVITY_MANAGER_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd();// ShutdownActivityManager
metricEnded(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();
}
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(PACKAGE_MANAGER_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd(); // ShutdownPackageManager
metricEnded(METRIC_PM);
// Shutdown radios.
shutdownTimingLog.traceBegin("ShutdownRadios");
metricStarted(METRIC_RADIOS);
shutdownRadios(MAX_RADIO_WAIT_TIME);
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(RADIO_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd(); // ShutdownRadios
metricEnded(METRIC_RADIOS);
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(MOUNT_SERVICE_STOP_PERCENT, null);
// If it's to reboot to install an update and uncrypt hasn't been
// done yet, trigger it now.
uncrypt();
}
shutdownTimingLog.traceEnd(); // SystemServerShutdown
metricEnded(METRIC_SYSTEM_SERVER);
saveMetrics(mReboot, mReason);
// Remaining work will be done by init, including vold shutdown
rebootOrShutdown(mContext, mReboot, mReason);
}在这个函数中，会将获取相应的Reason，并且保存在SystemProperties中。
/*
* 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") + (mReason != null ? mReason : "");
SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);
}发送有序的关机广播：
Intent intent = new Intent(Intent.ACTION_SHUTDOWN);
intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND | Intent.FLAG_RECEIVER_REGISTERED_ONLY);
mContext.sendOrderedBroadcastAsUser(intent,
UserHandle.ALL, null, br, mHandler, 0, null, null);并且测量发送关机广播的时间：
shutdownTimingLog.traceBegin("SendShutdownBroadcast");
Log.i(TAG, "Sending shutdown broadcast...");
...
shutdownTimingLog.traceEnd(); // SendShutdownBroadcast关闭ActivityManager
final IActivityManager am =
IActivityManager.Stub.asInterface(ServiceManager.checkService("activity"));
if (am != null) {
try {
am.shutdown(MAX_BROADCAST_TIME);
} catch (RemoteException e) {
}
}关闭PackageManager：
final PackageManagerService pm = (PackageManagerService)
ServiceManager.getService("package");
if (pm != null) {
pm.shutdown();
}关闭Radios：
shutdownRadios(MAX_RADIO_WAIT_TIME);我们来看一下shutdownRadios的实现：
private void shutdownRadios(final int timeout) {
// If a radio is wedged, disabling it may hang so we do this work in another thread,
// just in case.
final long endTime = SystemClock.elapsedRealtime() + timeout;
final boolean[] done = new boolean[1];
Thread t = new Thread() {
public void run() {
TimingsTraceLog shutdownTimingsTraceLog = newTimingsLog();
boolean radioOff;
TelephonyManager telephonyManager = mContext.getSystemService(
TelephonyManager.class);
radioOff = telephonyManager == null
|| !telephonyManager.isAnyRadioPoweredOn();
if (!radioOff) {
Log.w(TAG, "Turning off cellular radios...");
metricStarted(METRIC_RADIO);
telephonyManager.shutdownAllRadios();
}
Log.i(TAG, "Waiting for Radio...");
long delay = endTime - SystemClock.elapsedRealtime();
while (delay > 0) {
if (mRebootHasProgressBar) {
int status = (int)((timeout - delay) * 1.0 *
(RADIO_STOP_PERCENT - PACKAGE_MANAGER_STOP_PERCENT) / timeout);
status += PACKAGE_MANAGER_STOP_PERCENT;
sInstance.setRebootProgress(status, null);
}
if (!radioOff) {
radioOff = !telephonyManager.isAnyRadioPoweredOn();
if (radioOff) {
Log.i(TAG, "Radio turned off.");
metricEnded(METRIC_RADIO);
shutdownTimingsTraceLog
.logDuration("ShutdownRadio", TRON_METRICS.get(METRIC_RADIO));
}
}
if (radioOff) {
Log.i(TAG, "Radio shutdown complete.");
done[0] = true;
break;
}
SystemClock.sleep(RADIOS_STATE_POLL_SLEEP_MS);
delay = endTime - SystemClock.elapsedRealtime();
}
}
};
t.start();
try {
t.join(timeout);
} catch (InterruptedException ex) {
}
if (!done[0]) {
Log.w(TAG, "Timed out waiting for Radio shutdown.");
}
}这个方法可以看到，新起了线程去对Radio和Phone进行了关闭的操作。
在这个最后，会调用rebootOrShutdown方法：
/**
* Do not call this directly. Use {@link #reboot(Context, String, boolean)}
* or {@link #shutdown(Context, String, boolean)} instead.
*
* @param context Context used to vibrate or null without vibration
* @param reboot true to reboot or false to shutdown
* @param reason reason for reboot/shutdown
*/
public static void rebootOrShutdown(final Context context, boolean reboot, String reason) {
if (reboot) {
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 down
Vibrator vibrator = new SystemVibrator(context);
try {
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 power
Log.i(TAG, "Performing low-level shutdown...");
PowerManagerService.lowLevelShutdown(reason);
}在这边，会去判断是重启还是关机，如果要关机的话，将会去执行关机操作。
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