qtconnectivity "Device discovery aborted due to unexpected adapter changes"

Haponov

this error happens from time to time (on Ubuntu and Raspbian) while trying to repeatedly scan for BLE devices with deviceDiscoveryAgent
using http://doc.qt.io/qt-5/qbluetoothdevicediscoveryagent.html#QBluetoothDeviceDiscoveryAgent-1 like this:

#include "controller.h"
#include <QDebug>

Controller::Controller(QObject *parent) : QObject(parent)
{
qDebug()<<"found " <<QBluetoothLocalDevice::allDevices().size()<<" devices";
for (int i=0; i<QBluetoothLocalDevice::allDevices().size(); ++i)
{
qDebug()<< QString ("dongle found, address - %1").arg(QBluetoothLocalDevice::allDevices().at(i).address().toString());
}

m_deviceDiscoveryAgent = new QBluetoothDeviceDiscoveryAgent(this);

connect(m_deviceDiscoveryAgent, SIGNAL(deviceDiscovered(const QBluetoothDeviceInfo&)),
        this, SLOT(foundDevice(const QBluetoothDeviceInfo&)));
connect(m_deviceDiscoveryAgent, SIGNAL(error(QBluetoothDeviceDiscoveryAgent::Error)),
        this, SLOT(deviceScanError(QBluetoothDeviceDiscoveryAgent::Error)));
connect(m_deviceDiscoveryAgent, SIGNAL(finished()), this, SLOT(scanFinished()));
m_deviceDiscoveryAgent->start();

}

void Controller::foundDevice(const QBluetoothDeviceInfo &beacon)
{
if (beacon.coreConfigurations() & QBluetoothDeviceInfo::LowEnergyCoreConfiguration)
{
qWarning() << "Discovered LE Device name: " << beacon.name() << " Address: " << beacon.address().toString()
<< "rssi "<<beacon.rssi();
}
}

void Controller::deviceScanError(QBluetoothDeviceDiscoveryAgent::Error)
{
qWarning() << "and here errors go";
}

void Controller::scanFinished()
{
qDebug()<< "!!scan finished!!-------------------";
m_deviceDiscoveryAgent->stop();
QTimer::singleShot(2000, this, SLOT(startScan()));
}

void Controller::startScan()
{
qDebug()<< "==================scan started again=================";
qDebug()<<"list of discovered devices is empty - "
<< m_deviceDiscoveryAgent->discoveredDevices().isEmpty();
m_deviceDiscoveryAgent->start();
}

and such an error is nowhere on the internet except for sites like http://code.qt.io/cgit/qt/qtconnectivity.git/commit/?id=5382ada3cb21cfa2721e4f50ced2d288c156018b
can anyone explain what it means?

Thof

Have you found a solution? I'm in the same situation and looking for a stable solution!

Haponov

No. I gave up searching devices with QBluetoothDeviceDiscoveryAgent, as it does not seem "to like" being stopped and started again in the same thread. And frankly speaking stopping/starting it is useless.

Instead I go with bluez "hcitool lescan" in QProcess

AlexBlasche

The fix for this bug is stated in https://bugreports.qt.io/browse/QTBUG-53715. Next target are 5.6.2 and 5.7.1. Should be easy to cherry-pick as well.