To remind everyone in the very first place, I take no credit for the development of TWRP itself, which is all thanks to the great work of Team Win (@Dees-Troy , @bigbiff et al)
The idea of the app was just that to create a means to donate to me in the first place, and since I didn't want to make a "Hello WOrld" app just to get donations, I thought why not make an app that actually does something useful. Back from then, the app has come to gather a lot of features and is a really handy tool.
What does it do ? This app downloads a TWRP/CWM recovery image for your device and flashes it to the FOTAKernel partition of your phone.
It also allows you to backup the FOTAKernel and restore it or format it. (in case you want to remove TWRP later on)
Dafuq is FOTAKernel ? FOTAKernel is a partition on XPeria phones which contains a recovery-like bootsystem that is used to perform OTA (over the air) upgrades of your ROM from SONY. (If you have ever upgraded your ROM via the Sony Update Centre on your device, then your device reboots into the fotakernel which flashes the new android version to your phone. Once bootloader is unlocked, FOTAKernel is of no use anymore as OTA is not supported. It can be very cleverly used now as a pseudo recovery partition of the device.
Which devices are supported ? Xperia T, V, Z, ZL, Tablet Z (Wifi and LTE both) are currently supported. ***Xperia ZR, SP, Z1 and Z Ultra are supported too now ****
What are the requirements ? For the app to flash TWRP to FOTAKernel, you just need root and unlocked bootloader. But for TWRP to boot and work, you need to be on a kernel that supports the "extract_elf_ramdisk" method. Almost all kernels for custom ROMs like AOKP/CM/FXP/PAC/AOSPA/Omni have support for this feature. Among stock kernels, DoomKernel supports this. Please ask your kernel developer if FOTAKernel recovery support is present (and demand it to be added if not )
What are the advantages of this method ? Every time you flash a kernel, the recovery gets changed, because the recovery is present in the kernel. But if we are hotbooting a recovery in the fotakernel partiton, then even after flashing a new kernel (given that it supports extract_elf_ramdisk), your recovery is not changed. Thus even if the kernel's inbuilt recovery is broken, you can continue to use the recovery you have flashed onto your fotakernel.
What if I do not want to (or cannot afford to) buy the app ? Whatever the app does, can be done manually too using the instructions on this thread
Also the app is completely open source. The sources of the app as well as the sources from which I have built the recovery images are on https://github.com/championswimmer/Xperia_FOTAKernel_Manager_Android_App
Feel free to build yourself a copy from the source. I would appreciate if you do not distribute it though.
I HAZ A PROBLEM WITH DA APP. PLOX FIX IT!!! Please mention your problem on this thread asap. I will try to fix it. But no promises how soon that will happen. Being a paid app does not mean I will be providing 24x7 support. Again remember, just consider buying the app as donation for my developmental efforts on Xperias, not as a purchase of a premium service
Does not work on every circiumstance that I tested - open bootloader, closed bootloader, stock kernel, DooMKernel. To me this app is totally useless and no refund was possible, even within 15 Minutes! This App is a total rip-off for me!
Save your money and install ZUDualBootRecovery or a Kernel with FOTA Recovery build-im, what almost all root-Kernel have.