error when I combine bleak with gui

• bleak version: 0.7.1
• Python version: 3.7.7
• Operating System: MacOS Catalina 10.15.4

Description

Hi, I have a problem. I saw another issue about tkkinter. I’m trying to connect the bleak library with the graphics library. On windows everything works great, unfortunately again I have a problem with macOS. If it’s not the fault of the Bleak, I’m sorry.

What I Did

I send a code that scans and then connects and displays the notified data.

Very often ( 75% ) times when I connect I get a error:

File "main.py", line 251, in <module>
    loop.run_until_complete(run(device, loop))
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/asyncqt/__init__.py", line 309, in run_until_complete
    return future.result()
  File "main.py", line 237, in run
    async with BleakClient(address, loop=loop) as client:
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/bleak/backends/client.py", line 49, in __aenter__
    await self.connect()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/bleak/backends/corebluetooth/client.py", line 83, in connect
    manager = self._device_info.manager().delegate()
AttributeError: 'NoneType' object has no attribute 'delegate'

import sys
import asyncio
import os

from PyQt5.QtWidgets import QApplication, QProgressBar, QFileDialog
from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWidgets import QMainWindow, QLabel, QGridLayout, QWidget, QPushButton, QListWidget, QListWidgetItem
from PyQt5.QtCore import QSize 
from asyncqt import QEventLoop, QThreadExecutor
from PyQt5.QtWidgets import QDialog

import bleak
from bleak import discover, BleakClient

class MainWindow(QDialog):
    def __init__(self):
        super(MainWindow, self).__init__(None)

        self.setMinimumSize(QSize(500, 500))    
        self.setWindowTitle("Bleak GUI")         
        
        self.lDeviceCapt = QLabel("Device:", self)
        self.lDeviceCapt.resize(50, 32)
        self.lDeviceCapt.move(50, 50)
        
        self.lDeviceInfo = QLabel("[xxx]", self)
        self.lDeviceInfo.resize(200, 32)
        self.lDeviceInfo.move(200, 50)
        
        self.lCurrMessage = QLabel("", self)
        self.lCurrMessage.resize(200, 32)
        self.lCurrMessage.move(200, 100)
        
        self.lMessages = QListWidget(self)
        self.lMessages.resize(200, 300)
        self.lMessages.move(200,150)
        self.started = False
        
    def notify(self, msg):
        self.lMessages.addItem(str(msg))

    def did_connect(self, address):
        self.lDeviceInfo.setText(str(address))
    
app = QApplication(sys.argv)
loop = QEventLoop(app)
asyncio.set_event_loop(loop)

app = QtWidgets.QApplication(sys.argv)
mainWin = MainWindow()
mainWin.show()

devices_list = []

async def scan():
    devices = await discover()
    for d in devices:
        print(d)
        devices_list.append(d)

loop = asyncio.get_event_loop()
loop.run_until_complete(scan())
	
device = devices_list[0].address

def callback(sender, data):
    print(f"{sender}: {data}")
    mainWin.notify(data)

async def run(address, loop):

     async with BleakClient(address, loop=loop) as client:
        
        mainWin.did_connect(address)

        await client.start_notify(YOUR_UUID, callback)

        while True:
            await asyncio.sleep(5.0)
            if not await client.is_connected():
                print("Disconnect")
                break

with loop:
    loop.run_until_complete(run(device, run))

[dlech]

QBluetooth is basically the same as Bleak - it provides a common abstraction for cross-platform backends. You do not have to create your own backend. I’ve used it successfully with PyQt before. I didn’t think it was too difficult to translate the C++ examples to Python. Using QBluetooth seemed easier than trying to integrate asyncio into the Qt run loop.

[ivanjimenez]

QBluetooth is basically the same as Bleak - it provides a common abstraction for cross-platform backends. You do not have to create your own backend. I’ve used it successfully with PyQt before. I didn’t think it was too difficult to translate the C++ examples to Python. Using QBluetooth seemed easier than trying to integrate asyncio into the Qt run loop.

I’m trying to integrate bleak, pyqt5, asyncio, qasync. But I don’t think that qasync will be maintened in the future with support for Pyqt6 or above. PyQTBlueTooth is poor documented. I have scanned and connected a IMU sensor but I don’t know if you could publish some code using QtBluetooth for Python with examples with write_gatt_char, read_gatt_char, etc.

I apreciate your help. Thanks!!