Application crashed when I stop bluetooth scanning

helenebro

Hi,
I have an application where I want to communicate with BLE device. At the begin I start scanning. I would like stop scanning as soon as I have found my device. But when I do this, my application crashed.
I have no problem when I wait end of scanning.
Have you some ideas ?

#include "myapp.h"
#include <QCoreApplication>

MyApp::MyApp()
    : m_deviceDiscoveryAgent(0)
    , m_controller(0)
    , m_service(0)
{
    m_deviceDiscoveryAgent = new QBluetoothDeviceDiscoveryAgent(this);

    connect(m_deviceDiscoveryAgent, SIGNAL(deviceDiscovered(const QBluetoothDeviceInfo&)),
            this, SLOT(addDevice(const QBluetoothDeviceInfo&)));
    connect(m_deviceDiscoveryAgent, SIGNAL(error(QBluetoothDeviceDiscoveryAgent::Error)),
            this, SLOT(deviceScanError(QBluetoothDeviceDiscoveryAgent::Error)));
    connect(m_deviceDiscoveryAgent, SIGNAL(finished()), this, SLOT(scanFinished()));
    connect(m_deviceDiscoveryAgent, SIGNAL(canceled()), this, SLOT(scanCancel()));

    qDebug()<<("Scanning for devices...");
    m_deviceDiscoveryAgent->start();

}

MyApp::~MyApp()
{
    delete m_deviceDiscoveryAgent;
    delete m_controller;
    delete m_service;
}

void MyApp::addDevice(const QBluetoothDeviceInfo &device)
{
    if (device.coreConfigurations() & QBluetoothDeviceInfo::LowEnergyCoreConfiguration) {
        qDebug()<<device.address().toString();
        if(device.address().toString() == "xx:xx:xx:xx:xx:xx")
        {
            qDebug()<<">>> device found !"<<m_deviceDiscoveryAgent;
            m_deviceDiscoveryAgent->stop();
           // connectDevice(device);

        }
    }
}

void MyApp::scanFinished()
{
    qDebug()<<"scanFinished()";
}

void MyApp::scanCancel()
{
    qDebug()<<"scan cancel";
}

void MyApp::deviceScanError(QBluetoothDeviceDiscoveryAgent::Error error)
{
    if (error == QBluetoothDeviceDiscoveryAgent::PoweredOffError)
        qDebug()<<("The Bluetooth adaptor is powered off, power it on before doing discovery.");
    else if (error == QBluetoothDeviceDiscoveryAgent::InputOutputError)
        qDebug()<<("Writing or reading from the device resulted in an error.");
    else
        qDebug()<<("An unknown error has occurred.");
}

void MyApp::deviceConnected()
{
    qDebug()<<"deviceConnected, request discoverServices";
    m_controller->discoverServices();
}

void MyApp::deviceDisconnected()
{
    qWarning() << "Remote device disconnected";
}

void MyApp::connectDevice(const QBluetoothDeviceInfo& device)
{
    qDebug()<<"connectDevice";

    if (m_controller!=NULL) {
        m_controller->disconnectFromDevice();
        delete m_controller;
        m_controller = 0;
    }

    m_controller = new QLowEnergyController(device.address(),
                                            this);
    connect(m_controller, SIGNAL(error(QLowEnergyController::Error)),
            this, SLOT(controllerError(QLowEnergyController::Error)));
    connect(m_controller, SIGNAL(connected()),
            this, SLOT(deviceConnected()));
    connect(m_controller, SIGNAL(disconnected()),
            this, SLOT(deviceDisconnected()));
    connect(m_controller, SIGNAL(serviceDiscovered(QBluetoothUuid)),
            this, SLOT(serviceDiscovered(QBluetoothUuid)));
    connect(m_controller, SIGNAL(discoveryFinished()),
            this, SLOT(serviceScanDone()));
    m_controller->connectToDevice();
}

SGaist

Hi,

Where exactly does it crash ?

Note that you are missing a null pointer check for m_controller in deviceConnected

helenebro

It crash just after slots "scanCancel()".
This is output (console application):

Scanning for devices...
"xx:xx:xx:xx:xx:xa"
"xx:xx:xx:xx:xx:xb"
"xx:xx:xx:xx:xx:xx"
>>> device found ! QBluetoothDeviceDiscoveryAgent(0x23dc7c0)
scan cancel
Appuyez sur <ENTRÉE> pour fermer cette fenêtre...

and on console :

Starting of /path/of/MyAppTest...
/path/of/MyAppTest crashed
```.

SGaist

Can you get a stack trace for the crash ?

By the way, what OS and Qt version are you running ?