Kivy application does not work on Android

Question

I want write simple application in Python for Android using kivy. Sadly when I start example code I see only splash screen and few second later application finish work. There is a huge problem with debugging because adb on Linux Mint does not detect my device.

Can someone look at my code and tell my why? To build application I use buildozer. You can also see create_env script to check all dependencies are there.

Best regards. Draqun

EDIT:

I started debugging my application. Conclusion:

• buildozer + python3 + kivy is a bad idea
• if I use kivy.uix.button.Button when text attribute is str than I got exception "AttributeError: 'str' object has no attribute 'decode'"
• if I use kivy.uix.button.Button when text attribute is bytes than I got exception "ValueError: Button.text accept only str"

It looks like loop with no solution. Some idea when I should report it?

Exception is in .buildozer/android/platform/build/build/python-installs/pad/android/init.py" file so it does not look like kivy and/or buildozer exception.

Answer 1

I've used python-for android tool and faced with the same errors. But in my case, app didn't run at all - crashed from splash screen. Finally, I've found a solution. You can try the same way.

So my pipeline was python3 + python-for-android (p4a tool, python-for-android, from master branch) + kivy (1.10.1)

There is a file "_android.pyx" for android building recipe (full list of avaliable p4a recipes you can see by command p4a recipes). This file is, possibly, used by Buildozer, and exactly used by P4A during APK building procedure. You need to fix it.

You may find it's location in Ubuntu (for example) via:

sudo updatedb
locate _android.pyx

It's path should be something like:

~/.local/lib/python3.6/site-packages/pythonforandroid/recipes/android/src/android/_android.pyx

There should be a string:

python_act = autoclass(JAVA_NAMESPACE.decode('utf-8') + u'.PythonActivity')

so you should change it - something like this:

python_act = autoclass(str(JAVA_NAMESPACE) + u'.PythonActivity'),

or just use some hardcode:

python_act = autoclass("org/kivy/android/PythonActivity")

Or there might be the other decode() usage in sources.

The reason: differences between Python2 and Python3 - the decode() method is usable on the equivalent binary data type in either Python 2 or 3, but it can’t be used by the textual data type consistently between Python 2 and 3 because str in Python 3 doesn’t have the method decode function has different realisation in Python3. More details are here: pyporting features issues p4a's github

Hope, it will help you somehow.