Android关机流程解析---从reboot说起
- Android关机流程解析
-
在PowerManager的API文档中，给出了一个关机/重启接口：
public void reboot (String reason)
对于这个接口的描述很简单，就是几句话。接口的作用就是重启设备，而且，就算重启成功了也没有返回值。
需要包含REBOOT权限，也就是android.permission.REBOOT
唯一参数reason代表需要的特定重启模式，比如recovery，当然也可以为null。
--------------------------------上层空间--------------------------------1.frameworks/base/core/java/android/os/PowerManager.java
[java]
* Reboot the device. Will not return if the reboot is
* successful. Requires the {@link android.Manifest.permission#REBOOT}
* permission.
*
* @param reason code to pass to the kernel (e.g., "recovery") to
* request special boot modes, or null.
*/
public void reboot(String reason)
{
try {
mService.reboot(reason);
} catch (RemoteException e) {
}
}
public void reboot(String reason)
{
try {
mService.reboot(reason);
} catch (RemoteException e) {
}
}
mService为IPowerManager Binder接口服务。
[java]
public PowerManager(IPowerManager service, Handler handler)
{
mService = service;
mHandler = handler;
}
public PowerManager(IPowerManager service, Handler handler)
{
mService = service;
mHandler = handler;
}
2.frameworks/base/core/java/android/os/IPowerManager.aidl[java]
interface IPowerManager
{
...
void reboot(String reason);
...
}interface IPowerManager
{
...
void reboot(String reason);
...
}3.frameworks/base/services/java/com/android/server/PowerManagerService.java
[java]
public void reboot(String reason)
{
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);
if (mHandler == null || !ActivityManagerNative.isSystemReady()) {
throw new IllegalStateException("Too early to call reboot()");
}
final String finalReason = reason;
Runnable runnable = new Runnable() {
public void run() {
synchronized (this) {
ShutdownThread.reboot(getUiContext(), finalReason, false);
}
}
};
// ShutdownThread must run on a looper capable of displaying the UI.
mHandler.post(runnable);
// PowerManager.reboot() is documented not to return so just wait for the inevitable.
synchronized (runnable) {
while (true) {
try {
runnable.wait();
} catch (InterruptedException e) {
}
}
}
}
public void reboot(String reason)
{
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);if (mHandler == null || !ActivityManagerNative.isSystemReady()) {
throw new IllegalStateException("Too early to call reboot()");
}final String finalReason = reason;
Runnable runnable = new Runnable() {
public void run() {
synchronized (this) {
ShutdownThread.reboot(getUiContext(), finalReason, false);
}}
};
// ShutdownThread must run on a looper capable of displaying the UI.
mHandler.post(runnable);// PowerManager.reboot() is documented not to return so just wait for the inevitable.
synchronized (runnable) {
while (true) {
try {
runnable.wait();
} catch (InterruptedException e) {
}
}
}
}4.frameworks/base/services/java/com/android/server/pm/ShutdownThread.java
[java]
public static void reboot(final Context context, String reason, boolean confirm) {
mReboot = true;
mRebootSafeMode = false;
mRebootReason = reason;
shutdownInner(context, confirm);
}
public static void reboot(final Context context, String reason, boolean confirm) {
mReboot = true;
mRebootSafeMode = false;
mRebootReason = reason;
shutdownInner(context, confirm);
}
这里说明是需要重启，且不是安全模式，重启参数为传递下来的reason，shutdownInner的confirm参数是用来设置是否有确认提示框的，通过reboot接口调用重启是没有的，为false。重启的实现在run()中，因为ShutdownThread是Thread的扩展，所以run会自动运行。
[java]
public void run() {
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();
}
};
{
String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");
SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);
}
if (mRebootSafeMode) {
SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");
}
...
rebootOrShutdown(mReboot, mRebootReason);
}
public void run() {
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();
}
};
{
String reason = (mReboot ? "1" : "0") + (mRebootReason != null ? mRebootReason : "");
SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);
}
if (mRebootSafeMode) {
SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");
}
...
rebootOrShutdown(mReboot, mRebootReason);
}在重启前会将重启原因写入sys.shutdown.requested，如果没有则为空，如果是安全模式还会将persist.sys.safemode置1，之后会进行一些关机前的预处理，关闭ActivityManager以及MountService，最终调用rebootOrShutdown进行关机操作。
[java]
public static void rebootOrShutdown(boolean reboot, String reason) {
if (reboot) {
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) {
// 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.