Yes, you can add as many payment methods as you like to your account. See 'How do I add a payment method?' for more information.
Once you have more than one, you can switch between payment methods easily via the app. How? Just go to the 'Payment' section and press to select the one you want to use.
Please bear in mind, you can not use the same payment method in more than two accounts. If you want to pay for all your family's journeys on the same card, we recommend you add your family as users on your account. To see how, go to 'Can I add more users to my account?'