The solution to your problem is using an `` App Locker '' , which lets

The solution to your problem is using an "App Locker", which lets you protect selected apps with a password (or pattern). Each time you want to open a protected app, you then have to first "unlock" it. There might also be solutions permitting you to keep the "unlock" cached, e.g. for a confugured time span or place (e.g. when home) -- but as I don't need any app-locker I never remember which app offered that. Examples for such app-lockers are Smart App Protector(App Lock), supporting password, pattern, and even gesture unlock, and Smart AppLock (App Protector): Smart App Protector and Smart AppLock (Source: Google Play; click images for larger variant)