Circular errors with Java version and Android SDK

[SengerM]

Versions

• Python: 3.8.2
• OS: Xubuntu 20.04
• Buildozer: $ buildozer --version returns

# Check configuration tokens
Buildozer 1.0

Description

I wrote an extremely simple app with Kivy. The main.py file is

import kivy
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.properties import ObjectProperty
import numpy as np

class MyGrid(Widget):
	measurement_output = ObjectProperty(None)
	measurement_btn = ObjectProperty(None)

	def measure_btn(self):
		self.measurement_output.text = 'Just a random number for testing: ' + str(round(np.random.rand()*100))

class MyApp(App):
	def build(self):
		return MyGrid()

if __name__ == "__main__":
	MyApp().run()

and the my.kv file is

<MyGrid>:
	measurement_output: measurement_output_id
	measurement_btn: measurement_btn_id

	FloatLayout:
		size: root.width, root.height
		
		Label:
			id: measurement_output_id
			text: "-"
			size_hint: 1,.5
			pos_hint: {'x': 0, 'y': .5}

		Button:
			id: measurement_btn_id
			text: "Measure"
			on_press: root.measure_btn()
			size_hint: .5,.5
			pos_hint: {'x': 1/4, 'y': 0}

In my computer this works fine. Now I am trying to take it to my Android phone using Buildozer but cannot make it.
My starting point was this Kivy guide. I installed Buildozer with pip3 install buildozer and everything went fine. After that I installed all the dependencies as is detailed in this link. I have also done what is in the python-for-android for the errors related to java version. This last thing of java 8 broke a previous problem with the Android SDK which was again solved with sudo apt install android-sdk and the java error began again. So now I am trapped in a circle it seems, when I fix the java version I get the [ERROR]: Build failed: Requested API target 27 is not available, install it with the SDK android tool. and when I fix this error I get the current error.

I have already seen many other issues here on GitHub with no success.

buildozer.spec

Command:

$ buildozer android debug deploy run

Spec file:

[app]

# (str) Title of your application
title = Kivy app test

# (str) Package name
package.name = myapp

# (str) Package domain (needed for android/ios packaging)
package.domain = org.test

# (str) Source code where the main.py live
source.dir = .

# (list) Source files to include (let empty to include all the files)
source.include_exts = py,png,jpg,kv,atlas

# (list) List of inclusions using pattern matching
#source.include_patterns = assets/*,images/*.png

# (list) Source files to exclude (let empty to not exclude anything)
#source.exclude_exts = spec

# (list) List of directory to exclude (let empty to not exclude anything)
#source.exclude_dirs = tests, bin

# (list) List of exclusions using pattern matching
#source.exclude_patterns = license,images/*/*.jpg

# (str) Application versioning (method 1)
version = 0.1

# (str) Application versioning (method 2)
# version.regex = __version__ = ['"](.*)['"]
# version.filename = %(source.dir)s/main.py

# (list) Application requirements
# comma separated e.g. requirements = sqlite3,kivy
requirements = python3,kivy

# (str) Custom source folders for requirements
# Sets custom source for any requirements with recipes
# requirements.source.kivy = ../../kivy

# (list) Garden requirements
#garden_requirements =

# (str) Presplash of the application
#presplash.filename = %(source.dir)s/data/presplash.png

# (str) Icon of the application
#icon.filename = %(source.dir)s/data/icon.png

# (str) Supported orientation (one of landscape, sensorLandscape, portrait or all)
orientation = portrait

# (list) List of service to declare
#services = NAME:ENTRYPOINT_TO_PY,NAME2:ENTRYPOINT2_TO_PY

#
# OSX Specific
#

#
# author = © Copyright Info

# change the major version of python used by the app
osx.python_version = 3

# Kivy version to use
osx.kivy_version = 1.9.1

#
# Android specific
#

# (bool) Indicate if the application should be fullscreen or not
fullscreen = 0

# (string) Presplash background color (for new android toolchain)
# Supported formats are: #RRGGBB #AARRGGBB or one of the following names:
# red, blue, green, black, white, gray, cyan, magenta, yellow, lightgray,
# darkgray, grey, lightgrey, darkgrey, aqua, fuchsia, lime, maroon, navy,
# olive, purple, silver, teal.
#android.presplash_color = #FFFFFF

# (list) Permissions
#android.permissions = INTERNET

# (int) Target Android API, should be as high as possible.
#android.api = 27

# (int) Minimum API your APK will support.
#android.minapi = 21

# (int) Android SDK version to use
#android.sdk = 20

# (str) Android NDK version to use
#android.ndk = 17c

# (int) Android NDK API to use. This is the minimum API your app will support, it should usually match android.minapi.
#android.ndk_api = 21

# (bool) Use --private data storage (True) or --dir public storage (False)
#android.private_storage = True

# (str) Android NDK directory (if empty, it will be automatically downloaded.)
#android.ndk_path =

# (str) Android SDK directory (if empty, it will be automatically downloaded.)
#android.sdk_path =

# (str) ANT directory (if empty, it will be automatically downloaded.)
#android.ant_path =

# (bool) If True, then skip trying to update the Android sdk
# This can be useful to avoid excess Internet downloads or save time
# when an update is due and you just want to test/build your package
# android.skip_update = False

# (bool) If True, then automatically accept SDK license
# agreements. This is intended for automation only. If set to False,
# the default, you will be shown the license when first running
# buildozer.
# android.accept_sdk_license = False

# (str) Android entry point, default is ok for Kivy-based app
#android.entrypoint = org.renpy.android.PythonActivity

# (str) Android app theme, default is ok for Kivy-based app
# android.apptheme = "@android:style/Theme.NoTitleBar"

# (list) Pattern to whitelist for the whole project
#android.whitelist =

# (str) Path to a custom whitelist file
#android.whitelist_src =

# (str) Path to a custom blacklist file
#android.blacklist_src =

# (list) List of Java .jar files to add to the libs so that pyjnius can access
# their classes. Don't add jars that you do not need, since extra jars can slow
# down the build process. Allows wildcards matching, for example:
# OUYA-ODK/libs/*.jar
#android.add_jars = foo.jar,bar.jar,path/to/more/*.jar

# (list) List of Java files to add to the android project (can be java or a
# directory containing the files)
#android.add_src =

# (list) Android AAR archives to add (currently works only with sdl2_gradle
# bootstrap)
#android.add_aars =

# (list) Gradle dependencies to add (currently works only with sdl2_gradle
# bootstrap)
#android.gradle_dependencies =

# (list) add java compile options
# this can for example be necessary when importing certain java libraries using the 'android.gradle_dependencies' option
# see https://developer.android.com/studio/write/java8-support for further information
# android.add_compile_options = "sourceCompatibility = 1.8", "targetCompatibility = 1.8"

# (list) Gradle repositories to add {can be necessary for some android.gradle_dependencies}
# please enclose in double quotes 
# e.g. android.gradle_repositories = "maven { url 'https://kotlin.bintray.com/ktor' }"
#android.add_gradle_repositories =

# (list) packaging options to add 
# see https://google.github.io/android-gradle-dsl/current/com.android.build.gradle.internal.dsl.PackagingOptions.html
# can be necessary to solve conflicts in gradle_dependencies
# please enclose in double quotes 
# e.g. android.add_packaging_options = "exclude 'META-INF/common.kotlin_module'", "exclude 'META-INF/*.kotlin_module'"
#android.add_gradle_repositories =

# (list) Java classes to add as activities to the manifest.
#android.add_activites = com.example.ExampleActivity

# (str) OUYA Console category. Should be one of GAME or APP
# If you leave this blank, OUYA support will not be enabled
#android.ouya.category = GAME

# (str) Filename of OUYA Console icon. It must be a 732x412 png image.
#android.ouya.icon.filename = %(source.dir)s/data/ouya_icon.png

# (str) XML file to include as an intent filters in <activity> tag
#android.manifest.intent_filters =

# (str) launchMode to set for the main activity
#android.manifest.launch_mode = standard

# (list) Android additional libraries to copy into libs/armeabi
#android.add_libs_armeabi = libs/android/*.so
#android.add_libs_armeabi_v7a = libs/android-v7/*.so
#android.add_libs_arm64_v8a = libs/android-v8/*.so
#android.add_libs_x86 = libs/android-x86/*.so
#android.add_libs_mips = libs/android-mips/*.so

# (bool) Indicate whether the screen should stay on
# Don't forget to add the WAKE_LOCK permission if you set this to True
#android.wakelock = False

# (list) Android application meta-data to set (key=value format)
#android.meta_data =

# (list) Android library project to add (will be added in the
# project.properties automatically.)
#android.library_references =

# (list) Android shared libraries which will be added to AndroidManifest.xml using <uses-library> tag
#android.uses_library =

# (str) Android logcat filters to use
#android.logcat_filters = *:S python:D

# (bool) Copy library instead of making a libpymodules.so
#android.copy_libs = 1

# (str) The Android arch to build for, choices: armeabi-v7a, arm64-v8a, x86, x86_64
android.arch = armeabi-v7a

#
# Python for android (p4a) specific
#

# (str) python-for-android fork to use, defaults to upstream (kivy)
#p4a.fork = kivy

# (str) python-for-android branch to use, defaults to master
#p4a.branch = master

# (str) python-for-android git clone directory (if empty, it will be automatically cloned from github)
#p4a.source_dir =

# (str) The directory in which python-for-android should look for your own build recipes (if any)
#p4a.local_recipes =

# (str) Filename to the hook for p4a
#p4a.hook =

# (str) Bootstrap to use for android builds
# p4a.bootstrap = sdl2

# (int) port number to specify an explicit --port= p4a argument (eg for bootstrap flask)
#p4a.port =


#
# iOS specific
#

# (str) Path to a custom kivy-ios folder
#ios.kivy_ios_dir = ../kivy-ios
# Alternately, specify the URL and branch of a git checkout:
ios.kivy_ios_url = https://github.com/kivy/kivy-ios
ios.kivy_ios_branch = master

# Another platform dependency: ios-deploy
# Uncomment to use a custom checkout
#ios.ios_deploy_dir = ../ios_deploy
# Or specify URL and branch
ios.ios_deploy_url = https://github.com/phonegap/ios-deploy
ios.ios_deploy_branch = 1.7.0

# (str) Name of the certificate to use for signing the debug version
# Get a list of available identities: buildozer ios list_identities
#ios.codesign.debug = "iPhone Developer: <lastname> <firstname> (<hexstring>)"

# (str) Name of the certificate to use for signing the release version
#ios.codesign.release = %(ios.codesign.debug)s


[buildozer]

# (int) Log level (0 = error only, 1 = info, 2 = debug (with command output))
log_level = 2

# (int) Display warning if buildozer is run as root (0 = False, 1 = True)
warn_on_root = 1

# (str) Path to build artifact storage, absolute or relative to spec file
# build_dir = ./.buildozer

# (str) Path to build output (i.e. .apk, .ipa) storage
# bin_dir = ./bin

#    -----------------------------------------------------------------------------
#    List as sections
#
#    You can define all the "list" as [section:key].
#    Each line will be considered as a option to the list.
#    Let's take [app] / source.exclude_patterns.
#    Instead of doing:
#
#[app]
#source.exclude_patterns = license,data/audio/*.wav,data/images/original/*
#
#    This can be translated into:
#
#[app:source.exclude_patterns]
#license
#data/audio/*.wav
#data/images/original/*
#


#    -----------------------------------------------------------------------------
#    Profiles
#
#    You can extend section / key with a profile
#    For example, you want to deploy a demo version of your application without
#    HD content. You could first change the title to add "(demo)" in the name
#    and extend the excluded directories to remove the HD content.
#
#[app@demo]
#title = My Application (demo)
#
#[app:source.exclude_patterns@demo]
#images/hd/*
#
#    Then, invoke the command line with the "demo" profile:
#
#buildozer --profile demo android debug

Logs

alf@alf-Lenovo:~/Desktop/kivy_test$ buildozer android debug deploy run
# Check configuration tokens
# Ensure build layout
# Check configuration tokens
# Preparing build
# Check requirements for android
# Run 'dpkg --version'
# Cwd None
Debian 'dpkg' package management program version 1.19.7 (amd64).
This is free software; see the GNU General Public License version 2 or
later for copying conditions. There is NO warranty.
# Search for Git (git)
#  -> found at /usr/bin/git
# Search for Cython (cython)
#  -> found at /home/alf/.local/bin/cython
# Search for Java compiler (javac)
#  -> found at /usr/lib/jvm/java-8-openjdk-amd64/bin/javac
# Search for Java keytool (keytool)
#  -> found at /usr/lib/jvm/java-11-openjdk-amd64/bin/keytool
# Install platform
# Run 'git config --get remote.origin.url'
# Cwd /home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android
https://github.com/kivy/python-for-android.git
# Run 'git branch -vv'
# Cwd /home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android
* master 17dfa6a0 [origin/master] Merge pull request #2174 from kivy/release-2020.04.29
# Run '/usr/bin/python3 -m pip install -q --user \'appdirs\' \'colorama>=0.3.3\' \'jinja2\' \'six\' \'enum34; python_version<"3.4"\' \'sh>=1.10; sys_platform!="nt"\' \'pep517<0.7.0"\' \'toml\''
# Cwd None
# Apache ANT found at /home/alf/.buildozer/android/platform/apache-ant-1.9.4
# Android SDK found at /home/alf/.buildozer/android/platform/android-sdk
# Recommended android's NDK version by p4a is: 19c
# Android NDK found at /home/alf/.buildozer/android/platform/android-ndk-r19c
# Check application requirements
# Check garden requirements
# Compile platform
# Run '/usr/bin/python3 -m pythonforandroid.toolchain create --dist_name=myapp --bootstrap=sdl2 --requirements=python3,kivy --arch armeabi-v7a --copy-libs --color=always --storage-dir="/home/alf/Desktop/kivy_test/.buildozer/android/platform/build-armeabi-v7a" --ndk-api=21'
# Cwd /home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android
/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/toolchain.py:84: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
  import imp
[INFO]:    Will compile for the following archs: armeabi-v7a
[INFO]:    Found Android API target in $ANDROIDAPI: 27
Traceback (most recent call last):
  File "/usr/lib/python3.8/runpy.py", line 193, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.8/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/toolchain.py", line 1231, in <module>
    main()
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/entrypoints.py", line 18, in main
    ToolchainCL()
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/toolchain.py", line 688, in __init__
    getattr(self, command)(args)
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/toolchain.py", line 144, in wrapper_func
    ctx.prepare_build_environment(user_sdk_dir=self.sdk_dir,
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/build.py", line 296, in prepare_build_environment
    apis = get_available_apis(self.sdk_dir)
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/build.py", line 73, in get_available_apis
    targets = get_targets(sdk_dir)
  File "/home/alf/Desktop/kivy_test/.buildozer/android/platform/python-for-android/pythonforandroid/build.py", line 61, in get_targets
    targets = avdmanager('list', 'target').stdout.decode('utf-8').split('\n')
  File "/usr/local/lib/python3.8/dist-packages/sh.py", line 1549, in __call__
    return RunningCommand(cmd, call_args, stdin, stdout, stderr)
  File "/usr/local/lib/python3.8/dist-packages/sh.py", line 793, in __init__
    self.wait()
  File "/usr/local/lib/python3.8/dist-packages/sh.py", line 849, in wait
    self.handle_command_exit_code(exit_code)
  File "/usr/local/lib/python3.8/dist-packages/sh.py", line 877, in handle_command_exit_code
    raise exc
sh.ErrorReturnCode_1: 

  RAN: /home/alf/.buildozer/android/platform/android-sdk/tools/bin/avdmanager list target

  STDOUT:


  STDERR:
Exception in thread "main" java.lang.NoClassDefFoundError: javax/xml/bind/annotation/XmlSchema
	at com.android.repository.api.SchemaModule$SchemaModuleVersion.<init>(SchemaModule.java:156)
	at com.android.repository.api.SchemaModule.<init>(SchemaModule.java:75)
	at com.android.sdklib.repository.AndroidSdkHandler.<clinit>(AndroidSdkHandler.java:81)
	at com.android.sdklib.tool.AvdManagerCli.run(AvdManagerCli.java:213)
	at com.android.sdklib.tool.AvdManagerCli.main(AvdManagerCli.java:200)
Caused by: java.lang.ClassNotFoundException: javax.xml.bind.annotation.XmlSchema
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
	... 5 more

# Command failed: /usr/bin/python3 -m pythonforandroid.toolchain create --dist_name=myapp --bootstrap=sdl2 --requirements=python3,kivy --arch armeabi-v7a --copy-libs --color=always --storage-dir="/home/alf/Desktop/kivy_test/.buildozer/android/platform/build-armeabi-v7a" --ndk-api=21
# ENVIRONMENT:
#     SHELL = '/bin/bash'
#     SESSION_MANAGER = 'local/alf-Lenovo:@/tmp/.ICE-unix/1061,unix/alf-Lenovo:/tmp/.ICE-unix/1061'
#     QT_ACCESSIBILITY = '1'
#     COLORTERM = 'truecolor'
#     XDG_CONFIG_DIRS = '/etc/xdg/xdg-xubuntu:/etc/xdg:/etc/xdg'
#     XDG_SESSION_PATH = '/org/freedesktop/DisplayManager/Session0'
#     XDG_MENU_PREFIX = 'xfce-'
#     CLUTTER_BACKEND = 'x11'
#     LANGUAGE = 'en_US'
#     TERMINATOR_DBUS_PATH = '/net/tenshu/Terminator2'
#     LC_ADDRESS = 'es_AR.UTF-8'
#     LC_NAME = 'es_AR.UTF-8'
#     SSH_AUTH_SOCK = '/run/user/1000/keyring/ssh'
#     TERMINATOR_UUID = 'urn:uuid:f8609dc8-6140-4197-b2e9-bd0daf0660ab'
#     DESKTOP_SESSION = 'xubuntu'
#     LC_MONETARY = 'es_AR.UTF-8'
#     SSH_AGENT_PID = '1135'
#     XDG_SEAT = 'seat0'
#     PWD = '/home/alf/Desktop/kivy_test'
#     LOGNAME = 'alf'
#     XDG_SESSION_DESKTOP = 'xubuntu'
#     QT_QPA_PLATFORMTHEME = 'gtk2'
#     XDG_SESSION_TYPE = 'x11'
#     PANEL_GDK_CORE_DEVICE_EVENTS = '0'
#     GPG_AGENT_INFO = '/run/user/1000/gnupg/S.gpg-agent:0:1'
#     XAUTHORITY = '/home/alf/.Xauthority'
#     XDG_GREETER_DATA_DIR = '/var/lib/lightdm-data/alf'
#     GDM_LANG = 'en_US'
#     HOME = '/home/alf'
#     LC_PAPER = 'es_AR.UTF-8'
#     LANG = 'en_US.UTF-8'
#     LS_COLORS = 'rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.oga=00;36:*.opus=00;36:*.spx=00;36:*.xspf=00;36:'
#     XDG_CURRENT_DESKTOP = 'XFCE'
#     VTE_VERSION = '6001'
#     XDG_SEAT_PATH = '/org/freedesktop/DisplayManager/Seat0'
#     TERMINATOR_DBUS_NAME = 'net.tenshu.Terminator21a9d5db22c73a993ff0b42f64b396873'
#     LESSCLOSE = '/usr/bin/lesspipe %s %s'
#     XDG_SESSION_CLASS = 'user'
#     TERM = 'xterm-256color'
#     LC_IDENTIFICATION = 'es_AR.UTF-8'
#     GTK_OVERLAY_SCROLLING = '0'
#     LESSOPEN = '| /usr/bin/lesspipe %s'
#     USER = 'alf'
#     DISPLAY = ':0.0'
#     SHLVL = '1'
#     LC_TELEPHONE = 'es_AR.UTF-8'
#     LC_MEASUREMENT = 'es_AR.UTF-8'
#     XDG_VTNR = '7'
#     XDG_SESSION_ID = 'c2'
#     XDG_RUNTIME_DIR = '/run/user/1000'
#     LC_TIME = 'es_AR.UTF-8'
#     XDG_DATA_DIRS = '/usr/share/xubuntu:/usr/share/xfce4:/usr/local/share:/usr/share:/var/lib/snapd/desktop:/usr/share'
#     PATH = '/home/alf/.buildozer/android/platform/apache-ant-1.9.4/bin:/home/alf/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin'
#     GDMSESSION = 'xubuntu'
#     DBUS_SESSION_BUS_ADDRESS = 'unix:path=/run/user/1000/bus'
#     LC_NUMERIC = 'es_AR.UTF-8'
#     _ = '/usr/local/bin/buildozer'
#     PACKAGES_PATH = '/home/alf/.buildozer/android/packages'
#     ANDROIDSDK = '/home/alf/.buildozer/android/platform/android-sdk'
#     ANDROIDNDK = '/home/alf/.buildozer/android/platform/android-ndk-r19c'
#     ANDROIDAPI = '27'
#     ANDROIDMINAPI = '21'
# 
# Buildozer failed to execute the last command
# The error might be hidden in the log above this error
# Please read the full log, and search for it before
# raising an issue with buildozer itself.
# In case of a bug report, please add a full log with log_level = 2

In an early stage of the command execution the log shows:

# Search for Java compiler (javac)
#  -> found at /usr/lib/jvm/java-8-openjdk-amd64/bin/javac
# Search for Java keytool (keytool)
#  -> found at /usr/lib/jvm/java-11-openjdk-amd64/bin/keytool

I am really new to all this. I see that the javac compiler has the right version (i.e. java-8) however the keytool (I don't konw what this is) has the version 11, which is the one I had in my computer before downgrading to java 8. Might this be the problem?

[AndreMiras]

Yes this is 100% the problem https://github.com/kivy/python-for-android/blob/v2020.04.29/doc/source/troubleshooting.rst#errors-related-to-java-version

[SamedBll]

Is there any development in the year 2023?