Most of the Android smartphones come with three hard keys – power, volume up and volume down. The Samsung Galaxy phones also have an extra hard Home key. Similarly some of the LG phones also have a hard key for camera. Sometimes when you flash a new ROM ported for your device, one or more of the hard keys may stop to function. Because they were mapped for some other device. In order to make the hard keys work properly, you have to remap them. You may also want to remap the hard keys to make them do something else other than the intended use. For example, you may want to use the volume down key for taking a picture with your camera.
For all these key remapping needs, you can use an app called Button Remapper. This app has been around since the days of Ice Cream Sandwich and claims to work for the latest Android Lollipop too. The app requires root permissions so that it can make changes to the system keymap files, therefore you need a rooted device. If your device is not rooted then you can use Kingo Root to root your Android smartphone.
As you launch the Button Remapper app, it displays you the current mapping of all the hard keys on your phone including power, volume up, volume down, camera, home, media playback buttons etc. You can touch any one of them in the list to proceed with their remapping.
On the remapping screen, you have to choose an action for the selected hard key and a state. For the action you can choose from power, home, menu, back, search, volume up, volume down and camera. For the state you can choose either wake or wake dropped. The wake state turns on the device when you press the key while the wake dropped state keeps the device screen off even when you press the key.
After remapping the key, you may have to reboot the device to make the new keymap work. If you are not satisfied with the new keymap, then you can always revert back to the old key actions using the same method.
Conclusion: The Button Remapper app makes it very easy to remap hard keys on your Android device. This is very useful when you are installing new ROMs and the hard keys are not working as expected.
You can download Button Remapper from http://forum.xda-developers.com/showthread.php?t=850464.