How to Get Android L's Navigation Bar on Your Nexus Running 4.0+
If you want to try out some of the new features in Android L, but can't run the developer preview on your Nexus—or simply don't want to—there's still hope. You don't actually need to be running Android L to try out some of the new improvements.
To make the navigation bar even more simple, Google has replaced the old soft key designs with three shapes: a circle, square, and triangle. The design creates an overall cohesiveness with the new OS theme.
Getting the new navigation bar theme will require you to root your Nexus and install the Xposed Framework, but both of these requirements can be achieved in less than five minutes if you haven't already accomplished them.
After getting your device ready, install the Android L Navigation Bar APK onto your Nexus device.
After downloading and installing the mod, make sure to properly activate through Xposed by checking the module in the Download section of the installer, then rebooting your device. Your L soft keys will be applied after the device has booted back up.
The soft keys are a fraction bigger and slightly rounder than the ones found in L, so if you decide to give in and try out Android L before its official release, take a look at our guides on doing so through Windows or the fastboot method.