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Tap into native Android and iOS APIs with Pyjnius and Pyobjus

· 3 min read
Feodor Fitsner
Feodor Fitsner
Flet founder and developer

When building mobile apps with Flet, you may need to interact directly with platform-specific APIs. Whether it’s accessing system information, managing Bluetooth devices, or working with user preferences, Pyjnius and Pyobjus by Kivy provide a seamless way to bridge Python with Java (for Android) and Objective-C (for iOS).

You can now integrate both Pyjnius and Pyobjus into your Flet apps! 🚀

Pyjnius for Android​

Pyjnius is a Python library for accessing Java classes using the Java Native Interface (JNI).

Adding to a project​

Add pyjnius dependency for Android builds only (other settings in pyproject.toml were omitted for brevity):

[project]
name = "pyjnius_demo"
version = "0.1.0"
dependencies = [
  "flet==0.27.1"
]

[tool.flet.android]
dependencies = [
  "pyjnius"
]

Usage examples​

Here are some example of how Pyjnius can be used in your Flet Android app.

Getting Android OS details​

from jnius import autoclass

# Get Build and Build.VERSION classes
Build = autoclass('android.os.Build')
Version = autoclass('android.os.Build$VERSION')

# Get OS details
device_model = Build.MODEL
manufacturer = Build.MANUFACTURER
brand = Build.BRAND
hardware = Build.HARDWARE
product = Build.PRODUCT
device = Build.DEVICE
os_version = Version.RELEASE
sdk_version = Version.SDK_INT

Listing Bluetooth devices​

from jnius import autoclass

# Get BluetoothAdapter instance
BluetoothAdapter = autoclass('android.bluetooth.BluetoothAdapter')
bluetooth_adapter = BluetoothAdapter.getDefaultAdapter()

if bluetooth_adapter is None:
    print("Bluetooth not supported on this device")
else:
    if not bluetooth_adapter.isEnabled():
        print("Bluetooth is disabled. Please enable it.")
    else:
        print("Bluetooth is enabled.")

        # Get paired devices
        paired_devices = bluetooth_adapter.getBondedDevices()
        for device in paired_devices.toArray():
            print(f"Device Name: {device.getName()}, MAC Address: {device.getAddress()}")

Accessing the Activity​

App main activity instance can be retrieved with the following code:

import os
from jnius import autoclass

activity_host_class = os.getenv("MAIN_ACTIVITY_HOST_CLASS_NAME")
assert activity_host_class
activity_host = autoclass(activity_host_class)
activity = activity_host.mActivity

Heck, you can basically call any Android API using Pyjnius - endless posibilities!

Check complete Flet Pyjnius example.

For more Pyjnius examples and API refer to the Pyjnius Documentation.

...or just use ChatGPT (or your favorite LLM) to get more ideas and solutions! 😅

Pyobjus for iOS​

Pyobjus is a library for accessing Objective-C classes as Python classes using Objective-C runtime reflection.

Adding to a project​

Add pyobjus dependency for iOS builds only (other settings in pyproject.toml were omitted for brevity):

[project]
name = "Pyjnius"
version = "0.1.0"
dependencies = [
  "flet==0.27.1"
]

[tool.flet.ios]
dependencies = [
  "pyobjus"
]

Usage examples​

The simplest example​

from pyobjus import autoclass

NSString = autoclass('NSString')
text = NSString.alloc().initWithUTF8String_('Hello world')
print(text.UTF8String())

Getting OS details​

from pyobjus import autoclass
from pyobjus.dylib_manager import load_framework, INCLUDE

# Load Foundation framework
load_framework(INCLUDE.Foundation)

# Get NSProcessInfo instance
NSProcessInfo = autoclass('NSProcessInfo')
process_info = NSProcessInfo.processInfo()

# Retrieve OS version as a string
os_version = process_info.operatingSystemVersionString.UTF8String()

print(f"iOS Version: {os_version}")

Working with app user settings​

from pyobjus import autoclass, objc_str

NSUserDefaults = autoclass('NSUserDefaults')

key = "pyobjus_hello_world_key"
value = "Hello, world!"

# set key
NSUserDefaults.standardUserDefaults().setObject_forKey_(objc_str(value), objc_str(key))

# get key
ret = NSUserDefaults.standardUserDefaults().stringForKey_(objc_str(key))

assert ret.UTF8String() == value

Check complete Flet Pyobjus example.

For more Pyobjus examples and API refer to the Pyobjus Documentation.

Plyer challenge​

There is a Plyer project by Kivy team which uses both Pyjnius and Pyobjus under the hood.

It's not ported to Flet yet. You can either get more usage examples for Android and iOS from there or help us with porting it to Flet.