How to keep your personal stuff private when lending your phone to a friend

It’s easy to keep your data private on an Android phone when it’s always in your hand. Just use a strong password, encrypt your device, and no one’s getting your stuff.
What about when you actually want a friend or acquaintance to see something on your phone? You could be handing them them all your private data. So should you hover over their shoulder, waiting to snatch the phone away? Nah, that’s rude. You can use a few apps and file system tricks to make sure your private stuff stays private.

Showing Off Your Photos

When someone shows you a photo on their phone, there’s always a temptation to swipe around and look at a few more. Don’t lie—you know you want to. This is probably one of the most common reasons you hand your phone to someone else. To gently remind people to keep their noses out of your business, there’s a great app called Focus.

Keep people focused on the photos you want them to see, not poking around in the Gallery.

With Focus, you to select one or more photos from your gallery app and use the share menu to share them to the Focus app. This locks the device into viewing only those images. Leaving the screen will ask for a PIN code, which presumably only you will know. There’s even an option to beep if someone tries to leave Focus without telling you, but that’s just if you’re particularly distrustful of your friends. The free version of Focus has ads, but the full version is only $1.
Android Gallery apps also obey the “hidden” folder rules, which is another way to obfuscate images you don’t want everyone to see. Simply use a file manager to change the name of the folder you want to hide. Add a period to the beginning of the name, and the Gallery won’t display it by default.

All Your Other Files

Let’s say you’ve got some private files on your device that you just don’t want showing up in the gallery or other apps at all. Whatever those might be (I’m not here to judge) you can hide them from all apps on the device by creating a new file and putting it in the right place.

A .nomedia file is like a cloaking device for the Android file system.

To do this you need a file browser like Sliding Explorer or Solid Explorer. Find the folder where the photos in question are, and add a new file with the file manager. When asked for the name, simply input “.nomedia “ and accept. This blank file acts as a flag to the Android file indexer to skip the folder, so nothing contained therein will appear in other apps or in searches. The only way to access the files is to use the file browser to navigate to it manually. If you don’t know where the files are, they might as well be invisible. This goes a step past making a folder hidden by adding a period to the start of the folder name.
This is actually a handy trick to know even if you’re not hiding personal things. If an app is cluttering up your gallery with its image assets, drop a .nomedia file in its folder and other apps will stop indexing it. The same goes for audio and video files that show up in your multimedia apps. Developers aren’t always cautious enough with the files they leave on a device, but it’s an easy fix.
There are also apps that claim to be “file lockers” that will store your files securely. Many of these apps in the Play Store are actually just doing the .nomedia trick for you. There are some that offer a way to encrypt your files and store them in a private directory, which is maybe overkill if all you want to do is keep people away from sensitive files when you allow them to use your phone. Use these at your own risk—if something goes wrong with the app, your files could end up corrupted or locked forever.

Apps

Maybe you have that friend who likes to post embarrassing Facebook updates on other people’s profiles. You can stymie this social assault the next time he or she has your phone clutched in their mischievous claw. You can lock down any app you want to keep it secure with an app like Smart App Locker.

Keep people from nosing around in your important apps.

There are a variety of apps that accomplish the same task, but Smart App Locker is well supported and gets high praise from users. With Smart App Locker you can choose sensitive apps like Facebook, Gallery, Twitter, and banking apps, and put them behind a passcode. This app supports PINs or pattern locks, and there’s even a sneaky mode that makes the password entry screen look like a force close dialog.
Obviously the best way to keep people out of your stuff is never to let them touch your phone, but that’s not terribly nice, nor practical. All it takes are a few tweaks and you can avoid undue embarrassment.

-Ryan Whitwam from greenbot