But if I call this variable from other Activity, is not initialized, but yes.. It has been previously initialized in another activity and already has values.
This variable must be filled in each activity? Can it not be really global?
all variable in your class are bound to the instance initiated in activity X.
You need to initialize it in every activity or use the class in the starter service and access the variable(s) through the instance in starter service.
You also can create process global vars in starter service and acces them from every activity.