I noticed on my iPhone that sometimes when I put an app in the background and then go to use another app, when I go back to the previous app, it looks like it would have to reload or refresh itself, often losing whatever it was showing before.
How do you prevent that from happening? Is the iPhone running out of memory or something?
iPhone 6, iOS 12
Use Background App Refresh
After you switch to a different app, some apps run for a short period of time before they're set to a suspended state. Apps that are in a suspended state aren’t actively in use, open, or taking up system resources. With Background App Refresh, suspended apps can check for updates and new content.
If you want suspended apps to check for new content, go to Settings > General > Background App Refresh and turn on Background App Refresh. If you quit an app from the app switcher, it might not be able to run or check for new content before you open it again.
Switch apps on your iPhone, iPad, or iPod touch - Apple Support
When you exit an app by pressing the HOME button or switching to another app the app that was exited should save its state to storage. If it doesn't that is a fault of the app, not iOS. Complain to the app developer.
iPhone sometimes closes your background apps automatically
