In most cases, you should save automatically when users create or change data (like the details for a contact) and leave the screen for another one. This lets users get things done without being interrupted.
Prompting to save
In rare cases, you should save more explicitly. Do this only when it would take a long time for users to recreate the changes. Prompting to save interrupts users and makes them indicate whether they want to save or delete data.
- Set up a Wi-Fi connection
- Type an email message
- Create a meeting invitation
- Edit an image or video
Show users the item was saved by changing it visually on the original screen. For example, you could use an animation to show that the alarm settings were saved. Avoid using notifications like toasts, which can interrupt users.
If you prompt users to save, keep positive action buttons (like Send, Save, or Done) inactive until users have made all of the required changes.