my android app will remind user of a particular task after every certain time(set by user). There could be as many task a user wants to be reminded of. I know alarm manager is a possible solution to notify user but I don't understand how I will notify user about each task. Will I have to have separate AlarmManger for each with separate Service running for each task? I am new to android programming. Thanks in advance.
I would suggest you to go through this document at Android Developers guide to learn all about services. And to be specific about alarm manager, you may refer here.
For reminding different tasks, you may provide unique ids for each intent you fire for particular task as mentioned here.