These days it has become very common to hand over your mobile phone to someone you meet if you want them to add their contact information in your phone. You also have to add your contact information in their smartphone in a similar manner. Some people do not even ask, they just hand you their phone and grab yours from your hand. In these situations, it is a good idea to protect some of your apps with a password so that nobody can access those apps and view your personal or sensitive information. You can use the free Norton App Lock app for Android to lock any app on your smartphone.
Norton App Lock uses two types of app protection locks – pattern lock or passcode lock. The pattern lock is exactly like the pattern lock used by Android screen-lock. The passcode lock requires you to enter four digits for locking or unlocking the apps. It uses the same passcode or pattern for locking various apps and also the Norton App Lock itself.
In the settings for the Norton App Lock, you can change the lock type (pattern or passcode), make pattern visible or invisible, change recovery email address (to be used when you forget the passcode or pattern), enable Sneak Peek (captures the photo of person using the phone) and more.
Norton App Lock requires you that you enable accessibility feature for it and only then you can use it to lock or unlock various apps. In the app list, you have to tap on an app and it will be instantly locked. If you tap on the same app again, it will be unlocked. You can also disable the Norton App Lock altogether when you are using the phone yourself and password protection of apps is not really needed.
You can download Norton App Lock for Android from https://play.google.com/store/apps/details?id=com.symantec.applock.