To prevent another person from seeing your Messenger or WhatsApp, you must block the applications with a password or key. It is as simple as installing an APP LOCKER or application protector.
The blocking apps on Android you can avoid unauthorized access to your private apps, such as access WhatsApp , Facebook or other. Unlike the lock screen that protects total access to the cell phone (and it is recommended to have it activated), in this case you will only block sensitive applications and you can allow them to use the rest. Best of all, these tools will allow you to unlock your apps even with your fingerprint (if the phone supports this feature).
Before downloading the following APP LOCK tools , check if your phone already has a factory function. For example, Xiaomi mobiles already incorporate a system to block applications, so it is not necessary to install an application like the ones mentioned.
Contents
Application to block applications on Android
What you need to install on the cell phone is an APP LOCK application. There are many in the Play Store but below I recommend some of the most popular and outstanding.
LockDown Pro
In addition to normal application protection , it can generate a deterrent screen that shows a calculator, which appears when trying to enter a blocked application and where the unlock code must be entered. Also, it can display a fake error message when trying to open a protected app, to trick intruders.
It offers a smart lock that keeps applications unlocked while the user is in a safe location, the phone is connected to a trusted WiFi network (same as Hexlock) or a Bluetooth device. They are useful functions to avoid having to constantly enter the lock code while you are at work, at home or in the car, for example.
This app allows you to protect photos and videos in a private gallery.
LockDown Pro Download : Google Play Link.
Lock (Smart App Lock)
Another powerful application with conventional blocking function, blocking based on the WiFi network to which the cell phone is connected, blocking according to the time, individual passwords for each application and unlocking with a fingerprint. It has other functions such as call blocking, 3G data blocking, remote cellular blocking, etc. This is a feature-packed app, so it can have a noticeable impact on team performance.
Download Lock : Google Play Link
Material Lock
Lightweight app, free of advertising and invasive permissions .
It is automatically disabled when you are connected to a WiFi network or a trusted Bluetooth device. That way you don’t have to constantly be unlocking your apps while you’re at home or in your car . It also allows you to configure a delay before the apps are blocked .
It offers fingerprint sensor support and remote unlocking of apps by sending an SMS from another cell phone .
Material Lock looks like it can also lock Messenger chat bubbles . What it does not offer is fingerprint support. It also doesn’t seem like you can set up a cheat screen (a false error notice for example) when trying to open a protected app. And it offers no protection against uninstallation .
Download Material Lock : play.google.com
Lock (App Lock)
From the developer DoMobile Lab, it is an application of the same hierarchy, with practically all the functions mentioned above. It is rated 4.4 / 5 and has been downloaded over 100 million times.
Download Lock App Lock : play.google.com
Other app blocking solutions
APPS temporary lock 
In this case I introduce you to Screen Fix , a function available on some devices with Android 5 and up. It should normally be found in the settings of your Android phone, “Security” option.
Basically, what it does is lock the cell phone to a single screen. If a friend asks you for a call, you can limit them to using only the screen to dial phone numbers, securely blocking the exit to other screens or applications of the device. To exit this mode, press and hold the multitasking button (“Overview” button).
Before using this feature you must configure a lock screen on Android (Configure> Security> Screen Lock) with a pattern, PIN or password (do not use the Swipe option). Then you have to activate the Screen Fix option in Configure> Security> Screen Fix.
Disguise blocked applications
Instead of that obvious screen showing that the application is blocked and that a code must be entered in order to open it, there is a more discreet option. With Oops! AppLock, when trying to open a locked app only an empty wallpaper will appear. To access you must press the volume buttons in the correct sequence. In other words, it is an unlock by physical buttons.
All you have to do is configure the blocking sequence by pressing the volume buttons. Then add the apps you want to block and configure the wallpaper and that’s it.
This tool is camouflaged under the name “K Note”. When you open it, a type of sheet will appear to write down notes. On that screen you will have to press the configured volume button sequence to enter the settings and also to add more protected applications.
Download Oops App Lock : Google Play
Protect apps on Android
Blocking apps on Android is a drastic but effective solution. If you prefer something more subtle, although less secure, you can hide the applications.