Background tasks and activity

Has anyone any idea 开发者_开发问答on how to solve the generic problems related to starting a task in background from an activity and when the task is finished posting the result to the activity that created ? (the activity might get destroyed in the meantime due to a orientation change ,or receiving a call , or might be in the process of destroying and recreation)

Depending of what you are doing you might consider using a Service as well.