如果确认重启，则调用PowerManagerService的lowLevelReboot函数，参数就是传递下来的reason，稍后分析。如果不是重启，即mReboot=false,那就是需要关机了，在shutdown函数中就能够知道。
/**
* 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.
* @param confirm true if user confirmation is needed before shutting down.
*/
public static void shutdown(final Context context, boolean confirm) {
mReboot = false;
mRebootSafeMode = false;
shutdownInner(context, confirm);
}
关机的时候需要震动，就是这里了SHUTDOWN_VIBRATE_MS，默认的定义是500ms。但是在代码上看，无论如何，最后都会调用一下lowLevelShutdown函数，也就是关机。逻辑上，这里可能是个问题，但是实际中，如果重启操作能够调用成功的话，整个系统都重启了，后边的代码当然不可能执行到了。
目光转回PowerManagerService
4.frameworks/base/services/java/com/android/server/PowerManagerService.java
/**
* Low-level function to reboot the device.
*
* @param reason code to pass to the kernel (e.g. "recovery"), or null.
* @throws IOException if reboot fails for some reason (eg, lack of
* permission)
*/
public static void lowLevelReboot(String reason) throws IOException {
nativeReboot(reason);
}
/**
* Low-level function turn the device off immediately, without trying
* to be clean. Most people should use
* {@link com.android.server.pm.internal.app.ShutdownThread} for a clean shutdown.
*/
public static void lowLevelShutdown() {
nativeShutdown();
}
很熟悉的字样native，是JNI调用了：
