Android : How to update third party widgets at BOOT_COMPLETED?

In my app the user can pick a widget from all widgets installed on the system and add it to a view.

If i start my app before booting of the device has completed, the widgets are not updated. If i wait until booting has completed and start then, it works.

Since these widgets are not my own ones, i dont have access to their WidgetProvider and cant update them when the event "BOOT_COMPLETED" happens.

How could i update them anyway (if even possible) ?