Have ever your friend or partner take your phone and make a joke on your social networks?
App Lock (Bloqueador Apps) can provide you a higher level of privacy to your device.
You can lock any apps, Facebook,Gmail, Gallery through PIN.
Some android devices with Lollipop version could show a blank page , it this happened please do the next steps:
Go to Configuration -> Security ->Apps that access Usage Data.
Then activate app permission.