Issue Compiling Matplotlib for Android (Buildozer)

[clarsendartois]

📝 Subject: Issue Compiling Matplotlib for Android (Buildozer)

Hey everyone, I'm trying to package my Kivy/KivyMD app for Android using Buildozer,
but it's failing when trying to compile Matplotlib from source.

---

📌 Issue

Buildozer gets stuck at:

[INFO]:    Building matplotlib for arm64-v8a
[INFO]:    matplotlib apparently isn't already in site-packages
[INFO]:    Building compiled components in matplotlib
[INFO]:    -> directory context /mnt/c/Users/darto/Documents/.buildozer/android/platform/build-arm64-v8a_armeabi-v7a/build/other_builds/matplotlib/arm64-v8a__ndk_target_21/matplotlib 
[DEBUG]:   -> running python3 setup.py build_ext -v

---

🛠 What I’ve Tried

1️⃣ Added matplotlib to requirements in buildozer.spec.
2️⃣ Checked dependencies (e.g., numpy, cycler).
3️⃣ Looked for a precompiled Matplotlib .whl but couldn’t find one.

---

❓ Questions

1️⃣ Is there a prebuilt Matplotlib wheel for Android that I can use instead of compiling?
2️⃣ If Matplotlib needs to be compiled, what dependencies do I need to include?
3️⃣ Any known workarounds to avoid this issue?

---

🙏 Any help would be greatly appreciated! Thanks in advance! 😊

[mriscoc]

I tried this minimal example:

"""Basic example for kivy_matplotlib_widget

Note:
    MatplotFigure is used when you have only 1 axis with lines only.
    For general purpose, please use MatplotFigureSubplot widget.

"""
from kivy.utils import platform

#avoid conflict between mouse provider and touch (very important with touch device)
#no need for android platform
if platform != 'android':
    from kivy.config import Config
    Config.set('input', 'mouse', 'mouse,disable_on_activity')

from kivy.lang import Builder
from kivy.app import App
import matplotlib.pyplot as plt
import kivy_matplotlib_widget #register all widgets to kivy register
import numpy as np

KV = '''
Screen
    figure_wgt:figure_wgt
    BoxLayout:
        orientation:'vertical'
        BoxLayout:
            size_hint_y:0.1
            Button:
                text:"home"
                on_release:app.home()
            ToggleButton:
                group:'touch_mode'
                state:'down'
                text:"pan" 
                on_release:
                    app.set_touch_mode('pan')
                    self.state='down'
            ToggleButton:
                group:'touch_mode'
                text:"zoom box"  
                on_release:
                    app.set_touch_mode('zoombox')
                    self.state='down'                
        MatplotFigure:
            id:figure_wgt
'''

plt.style.use('dark_background')

# Data for plotting
t = np.arange(0.0, 2.0, 0.01)
s = 1 + np.sin(2 * np.pi * t)

class Test(App):

    def build(self):  
        self.screen=Builder.load_string(KV)

        # Setup plot
        self.fig, self.ax1 = plt.subplots()
        self.ax1.set(xlabel='time (s)', ylabel='voltage (mV)', title='Test Matplot in Kivy')
        self.ax1.grid(alpha=0.5)

        return self.screen

    def on_start(self, *args):
        self.ax1.plot(t, s)
        self.screen.figure_wgt.figure = self.fig

    def set_touch_mode(self,mode):
        self.screen.figure_wgt.touch_mode=mode

    def home(self):
        self.screen.figure_wgt.home()
        
Test().run()

And compiles without problems with the develop branch of P4A and buildozer 1.5.1.dev0. buildozer.spec:

requirements = python3,kivy,numpy,matplotlib,kivy-matplotlib-widget
android.minapi = 24
android.archs = arm64-v8a
p4a.branch = develop
log_level = 2

Final log:

[INFO]:         matplottest: min API 24, includes recipes (freetype, hostpython3, jpeg, libffi, openssl, png, sdl2_image, sdl2_mixer, sdl2_ttf, sqlite3, python3, sdl2, kiwisolver, numpy, setuptools, pillow, six, matplotlib, pyjnius, android, kivy, cppy, python-dateutil, packaging, filetype, idna, chardet, fonttools, urllib3, requests, pyparsing, certifi, kivy-matplotlib-widget, cycler), built for archs (arm64-v8a)
[INFO]:    matplottest has compatible recipes, using this one
[INFO]:    # Copying android package to current directory
[INFO]:    # Android package filename not found in build output. Guessing...
[INFO]:    # Found android package file: /home/mrisco/kivy/kivy-matplottest/.buildozer/android/platform/build-arm64-v8a/dists/matplottest/build/outputs/apk/debug/matplottest-debug.apk
[INFO]:    # Add version number to android package
[INFO]:    # Android package renamed to matplottest-debug-0.1.apk
[DEBUG]:   -> running cp /home/mrisco/kivy/kivy-matplottest/.buildozer/android/platform/build-arm64-v8a/dists/matplottest/build/outputs/apk/debug/matplottest-debug.apk matplottest-debug-0.1.apk
No setup.py/pyproject.toml used, copying full private data into .apk.
Applying Java source code patches...
Applying patch: src/patches/SDLActivity.java.patch
# Copy /home/mrisco/kivy/kivy-matplottest/.buildozer/android/platform/build-arm64-v8a/dists/matplottest/build/outputs/apk/debug/matplottest-debug.apk to /home/mrisco/kivy/kivy-matplottest/bin/matplottest-0.1-arm64-v8a-debug.apk
# Android packaging done!
# APK matplottest-0.1-arm64-v8a-debug.apk available in the bin directory

[clarsendartois]

Hello, @mriscoc

Thanks for Testing This! 🎉

It looks like your build works fine with the develop branch of P4A and Buildozer 1.5.1.dev0.
I'm currently using:

• Buildozer version: (1.5.1.dev0)
• P4A branch: (develop)
• Android API level: (android.minapi = 24)

I'll try switching to the develop branch and updating Buildozer to 1.5.1.dev0 to see if that resolves the issue.

Question:

Did you need to manually install or modify anything else in your environment, or did it work out of the box after setting p4a.branch = develop?

Thanks again for your help! 😊

[mriscoc]

I did not change anything in the toolchain.

[clarsendartois]

📝 Subject: Buildozer Cython Dependency Conflict

Hey @mriscoc,

I've tested this, but I still have the same error even though I have Cython==0.29.37 installed and included in the requirements.

---

📌 Issue

When trying to build numpy for arm64-v8a, I get the following error:

[INFO]:    Building numpy for arm64-v8a
[INFO]:    numpy apparently isn't already in site-packages
[INFO]:    Writing cross file at: /tmp/android.meson.cross
[DEBUG]:   -> running pip install build[virtualenv] pip Cython>=3.0.6 ninja==1.11.1.1 meson==1.4.0 ...
[DEBUG]:        Collecting Cython>=3.0.6
[DEBUG]:          Using cached Cython-3.0.12-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (3.6 MB)
...
[DEBUG]:        ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
[DEBUG]:        buildozer 1.5.1.dev0 requires cython<3.0, but you have cython 3.0.12 which is incompatible.


💻 My Setup
WSL: Ubuntu 22.04 (WSL2)
Python: 3.11.5
Buildozer: 1.5.1.dev0
P4A Branch: develop

❓ Questions
1️⃣ Should I manually downgrade Cython inside the Buildozer environment?
2️⃣ Is there a workaround to force Buildozer to use Cython==0.29.37?
3️⃣ Do you have any additional recommendations?

Thanks in advance for your help! 😊

[mproeger]

With p4a.branch=master (default) and matplotlib==3.5.3 in requirements it works. I use ubuntu 24.04.

[mproeger]

It seems the problem is now solved in setuptools-scm 8.2.1 which was released today. There was a request for setuptools>=61 which is removed now. So there is no need for specifying a version for matplotlib. The errormessage still appears but the process continues without chrashing.