Building Android for Rpi4

General Notes

This is project experimental;
It is not guaranteed to build on all possible systems and it is not guaranteed to run on all Raspberry Pi configurations.
You need a fair amount of knowledge of Linux and Android to get this to work. Be warned!
Prerequisites:

• RAM is greater than 16GB
• CPU as much core as possible
• Free space is greater than 200GB

Of course, you need a Rpi4ModelB4G_RAM.
In addition, you also need a 7" HDMI Touch Screen 1024x600. There are many available. The one I use is from Waveshare.

Download Android source with local_manifests

Refer this link for install git and repo tool: https://source.android.com/setup/develop
Then, you can download the android source by the command:

mkdir android4pi && cd android4pi #create folder and cd to it
# remove --depth=1 if you want to care about the git history but the size of the download will increase
repo init --depth=1 -u https://android.googlesource.com/platform/manifest -b android-11.0.0_r37
git clone https://github.com/nguyenanhgiau/local_manifests .repo/local_manifests -b rpi4-a11-telephony
repo sync -j14 --force-sync

Reference download the android source: http://source.android.com/source/downloading.html

Building Kernel

Because the kernel project haven't integrated into AOSP building, so we have to build it separately.

sudo apt install gcc-aarch64-linux-gnu libssl-dev bc
cd android4pi/kernel/arpi
ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make lineageos_rpi4_defconfig
ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make Image.gz dtbs -j16

Building AOSP

Before building, you have to apply this patch https://github.com/android-rpi/device_arpi_rpi4/wiki/arpi-11-:-framework-patch

croot
source build/envsetup.sh
lunch rpi4-eng
make ramdisk systemimage vendorimage -j14

Use -j[n] option with make, if build host has a good number of CPU cores.
Reference: http://source.android.com/source/building.html

Writing the image to sdcard

croot
./scripts/android_flash_rpi4.sh sdb #suppose your sd card is sdb

Now, you can unplug your sdcard and plug on your rpi4, setup and enjoy!

ADB Connection

Because the Raspberry Pis do not have a USB OTG port, the only way to connect ADB is via Internet.
Plug your Raspberry Pi into your Ethernet LAN or wifi, then wait for it to be given an IP address.
After that, just run command:

$ adb connect <IP_ADDRESS>:5555 #192.168.1.10:5555

HAVE FUN!