Added a backend for python-for-android

and an example for kivy buildozer on android

CHANGELOG.rst

@@ -25,6 +25,7 @@ Fixed
 * Fixed ``BaseBleakClient.services_resolved`` not reset on disconnect on BlueZ
   backend. Merged #401.
 * Fixed RSSI missing in discovered devices on macOS backend. Merged #400.
+* Added python-for-android backend.
 
 
 `0.10.0`_ (2020-12-11)

README.rst

@@ -44,6 +44,7 @@ Features
 * Supports Windows 10, version 16299 (Fall Creators Update) or greater
 * Supports Linux distributions with BlueZ >= 5.43
 * OS X/macOS support via Core Bluetooth API, from at least OS X version 10.11
+* Android backend compatible with python-for-android
 
 Bleak supports reading, writing and getting notifications from
 GATT servers, as well as a function for discovering BLE devices.

bleak/__init__.py

@@ -16,7 +16,12 @@
 from bleak.__version__ import __version__  # noqa
 from bleak.exc import BleakError
 
+
 _on_rtd = os.environ.get("READTHEDOCS") == "True"
+if os.environ.get("P4A_BOOTSTRAP") is not None:
+    _system = "Python4Android"
+else:
+    _system = platform.system()
 
 _logger = logging.getLogger(__name__)
 _logger.addHandler(logging.NullHandler())
@@ -28,7 +33,7 @@
     _logger.addHandler(handler)
     _logger.setLevel(logging.DEBUG)
 
-if platform.system() == "Linux":
+if _system == "Linux":
     if not _on_rtd:
         # TODO: Check if BlueZ version 5.43 is sufficient.
         p = subprocess.Popen(["bluetoothctl", "--version"], stdout=subprocess.PIPE)
@@ -49,7 +54,14 @@
     from bleak.backends.bluezdbus.client import (
         BleakClientBlueZDBus as BleakClient,
     )  # noqa: F401
-elif platform.system() == "Darwin":
+elif _system == "Python4Android":
+    from bleak.backends.p4android.scanner import (
+        BleakScannerP4Android as BleakScanner,
+    )  # noqa: F401
+    from bleak.backends.p4android.client import (
+        BleakClientP4Android as BleakClient,
+    )  # noqa: F401
+elif _system == "Darwin":
     try:
         from CoreBluetooth import CBPeripheral  # noqa: F401
     except Exception as ex:
@@ -62,7 +74,7 @@
         BleakClientCoreBluetooth as BleakClient,
     )  # noqa: F401
 
-elif platform.system() == "Windows":
+elif _system == "Windows":
     # Requires Windows 10 Creators update at least, i.e. Window 10.0.16299
     _vtup = platform.win32_ver()[1].split(".")
     if int(_vtup[0]) != 10:
@@ -80,7 +92,7 @@
     from bleak.backends.dotnet.scanner import BleakScannerDotNet as BleakScanner  # noqa
     from bleak.backends.dotnet.client import BleakClientDotNet as BleakClient  # noqa
 else:
-    raise BleakError(f"Unsupported platform: {platform.system()}")
+    raise BleakError(f"Unsupported platform: {_system}")
 
 # for backward compatibility
 discover = BleakScanner.discover

bleak/backends/p4android/characteristic.py

@@ -0,0 +1,102 @@
+from uuid import UUID
+from typing import Union, List
+
+from bleak.backends.characteristic import BleakGATTCharacteristic
+from bleak.backends.descriptor import BleakGATTDescriptor
+from bleak.exc import BleakError
+
+from jnius import autoclass
+
+
+class _java:
+    BluetoothGattCharacteristic = autoclass(
+        "android.bluetooth.BluetoothGattCharacteristic"
+    )
+
+    CHARACTERISTIC_PROPERTY_DBUS_NAMES = {
+        BluetoothGattCharacteristic.PROPERTY_BROADCAST: "broadcast",
+        BluetoothGattCharacteristic.PROPERTY_EXTENDED_PROPS: "extended-properties",
+        BluetoothGattCharacteristic.PROPERTY_INDICATE: "indicate",
+        BluetoothGattCharacteristic.PROPERTY_NOTIFY: "notify",
+        BluetoothGattCharacteristic.PROPERTY_READ: "read",
+        BluetoothGattCharacteristic.PROPERTY_SIGNED_WRITE: "authenticated-signed-writes",
+        BluetoothGattCharacteristic.PROPERTY_WRITE: "write",
+        BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE: "write-without-response",
+    }
+
+    NOTIFICATION_DESCRIPTOR_UUID = "00002902-0000-1000-8000-00805f9b34fb"
+
+
+class BleakGATTCharacteristicP4Android(BleakGATTCharacteristic):
+    """GATT Characteristic implementation for the python-for-android backend"""
+
+    def __init__(self, java, service_uuid: str):
+        super(BleakGATTCharacteristicP4Android, self).__init__(java)
+        self.__uuid = self.obj.getUuid().toString()
+        self.__handle = self.obj.getInstanceId()
+        self.__service_uuid = service_uuid
+        self.__descriptors = []
+        self.__notification_descriptor = None
+
+        self.__properties = [
+            name
+            for flag, name in _java.CHARACTERISTIC_PROPERTY_DBUS_NAMES.items()
+            if flag & self.obj.getProperties()
+        ]
+
+    @property
+    def service_uuid(self) -> str:
+        """The uuid of the Service containing this characteristic"""
+        return self.__service_uuid
+
+    @property
+    def handle(self) -> int:
+        """The handle of this characteristic"""
+        return self.__handle
+
+    @property
+    def uuid(self) -> str:
+        """The uuid of this characteristic"""
+        return self.__uuid
+
+    @property
+    def properties(self) -> List:
+        """Properties of this characteristic"""
+        return self.__properties
+
+    @property
+    def descriptors(self) -> List:
+        """List of descriptors for this service"""
+        return self.__descriptors
+
+    def get_descriptor(
+        self, specifier: Union[str, UUID]
+    ) -> Union[BleakGATTDescriptor, None]:
+        """Get a descriptor by UUID (str or uuid.UUID)"""
+        if isinstance(specifier, int):
+            raise BleakError(
+                "The Android Bluetooth API does not provide access to descriptor handles."
+            )
+
+        matches = [
+            descriptor
+            for descriptor in self.descriptors
+            if descriptor.uuid == str(specifier)
+        ]
+        if len(matches) == 0:
+            return None
+        return matches[0]
+
+    def add_descriptor(self, descriptor: BleakGATTDescriptor):
+        """Add a :py:class:`~BleakGATTDescriptor` to the characteristic.
+
+        Should not be used by end user, but rather by `bleak` itself.
+        """
+        self.__descriptors.append(descriptor)
+        if descriptor.uuid == _java.NOTIFICATION_DESCRIPTOR_UUID:
+            self.__notification_descriptor = descriptor
+
+    @property
+    def notification_descriptor(self) -> BleakGATTDescriptor:
+        """The notification descriptor.  Mostly needed by `bleak`, not by end user"""
+        return self.__notification_descriptor