There are people that are very fond of reading WhatsApp conversations on other people's phones. If you think you know one of these people, you should download Lock for WhatsApp for Android.
Establish a PIN or a gesture pattern to access WhatsApp
Lock for WhatsApp is an application that installs a security barrier for the access to WhatsApp on your phone. You can configure a personal PIN or a gesture pattern to unlock the application. Thus, you can be sure that any nosy person is to going to find it complicated to read what he/she shouldn't.
Another way of protecting your privacy.
Lock for WhatsApp doesn't use up too many resources and keeps things quite simple. It is easy to configure and allows you to decide when to activate the lock and the type of password that unlocks it.
Lock WhatsApp and protect your messages from prying eyes.