After further research, i found that requestPermission only works on Android M. If i just include the permissions i needed in android manifest file, how does android ask user for the permission granted? For example, access fine location permission. I try including the requestPermission but never see the dialog.
Before Marshmallow, all the permissions are granted at installation time. That's why you don't see a dialog requesting permission on Lollipop and previous versions on runtime.
Check this out: Runtime Permissions. It only applies to Marshmallow and above.