Good start explaining it, but I will explain two ways one is not whether it can actually do for not having tested and another which is what I did
begin, we first need to look we have the same rom installed for internet, which is easy to find out if we have the same factory or have conducted an official upgrade, well, first look for the rom (download it there are places in ftf my case format.
we add the zip extension. (to open with winrar we smooth) open it and extract the file system.sin (It is an image of a partition with android specifically ext4 file system) basically good thing to do is extract the contents file not we use our flashtools I specifically 64-bit version (by the way as usual we have properly configured the adb drivers (for this point is not necessary but for other things that you wanted in the future if), well once opened flashtool in the tools menu and select the drop down menu in the editor without copcion select the file without have extracted (system.sin) and click on the button extract data (patience it is 1 gig)
now in the same location where we had the sistem.sin have another file called system.ext4, this is the image itself and we mount it with any software ext2explorer use in my case.
Open ext2explorer (must be done with administrator) open the file menu option and click on the open image and open the file system.ext4
appear on the right side as a drive and double click on the now navigate to the path / app and will be within the SystemUI.apk file, press the right mouse button on the shortcut menu and click on save and choose where to save it, we can do it directly on our mobile sd, and I'll copy it for example through linux command from my own mobile as the mobile when I boot my xperia menu appears and I can at least open the terminal
the other way is using adb commands (this already you can find for yourselves because I chooses the other option which controlled more anyway for that adb controleis what you have to do is copy the file in SystemUI.apk directory / system / app and restart mobile)
either continuous, once copied the file, if you happens as ami the button to go back does not appear (because your controls are on the screen) not you be forced to restart the phone, right after you restart your mobile beware because if we open an application we can not change to another, which will open the terminal (I recommend Android terminal Emulator because we can use the special characters that are not in the virtual keyboard android as the character pipe |), if you do not have terminal linux, what thou must do is open google get settled one to play without touching anything when finished press to open from google own play to spare you restart the phone, remember that you can not change once the app opens not because we have the buttons to return home and recent apps, well once we get done this as root by typing in your console
and we trace the system partition in read-write mode we must first know what the referenced device / system to esllo write the following: mount | grep / system (the pipe character is written keeping the volume up key without release by pressing the letter L) and you leave something like this
/ dev/block/platform/msm_sdcc.1/by-name/System / system ext4 ro, relatime, discard, data = orderer 0 0
apuntaros well so far before the second / system that is the device (partition) that is to be mounted in read mode escribura
for this use the following command
mount-o remount, rw / dev/block/platform/msm_sdcc.1/by-name/System / system
This makes it possible to write to the system partition, right after this you can run the following command
cp / sdcard / SystemUI.apk / system/app7
replace / sdcard / to the path in your sd where you COPIED your SystemUI.apk
after that ye turn reiniciais and have already solved your virtual buttons
One more thing on some devices need to run something from the adb, because when trying to put the system partition in read write mode the system will check and restart the phone, I think this is some ñapa some manufacturers that have done to prevent touch the core in the other phone is not whether something will occur or own the xperia but do not know if there is anything that is used through adb, if you came to the above, and I quedasteis at the point where the it restarts without letting only put the partition in read mode escribura descargaros you can try an application called fixer-reboot remount, adb comes with its own, which should not be a problem anyway as I restarted automatically when ye enter instead of opening the terminal what you have to do is go to settings and activate developer options assuring you that this active USB debugging is imperative to use adb
good once you link to download remount reboot fixer what decompress (sorry I can not provide a link of where to download but if someone costs is provided zip email or whatever and you climb it, mostly because I'm hardly ever at home and I guess it would be difficult to maintain the active link.
Well to correct what the automatic restart after the reboot remount fixer unzipped run a batch file install.bat, I think I remember to do it as administrator (this applies to try to unlock the bootloader without success) and has served me help you to correct the core, well the mess when you run this theme will correct (I can not remember if I restarted the phone but if you follow the instructions on screen will not have any good problem once done this I'm not sure if I restart the phone, but I recommend it, and from there turn back to the point of mounting the partition in read mode escribura and follow the steps once copied SystemUI.apk to the location that corresponds to the phone and reiniciais
I hope I have been helpful
PS: I did not realize that this product has the option to add a file upload so the remount rebootfix