Issues with Qt Bluetooth Scanner (android)

[ahsan737]

Greetings,
I have defined Bluetooth Scanner in Class A (bluetooth_server) and I want to display the scanned available devices in Class B.
I have done it but it is working inefficiently, the problem is that scanned devices don't always show up in ListView, sometimes I need to close the app and make several try to display available devices.

• Also, the scanner works fine if I turn off Bluetooth enter the app and then turn it on.

[J.Hilk]

@ahsan737
do you continuously scan, or only one scan ?

There's no guarantee that all devices will be found on the first scan

[ahsan737]

@j-hilk only once using signal/slot of QBluetoothDeviceDiscoveryAgent.
here is the code.

**Class A (bluetooth_server)**

    agent = new QBluetoothDeviceDiscoveryAgent;
    connect(agent, SIGNAL(deviceDiscovered(QBluetoothDeviceInfo)),
            this, SLOT(deviceDiscovered(QBluetoothDeviceInfo)));

    agent->start();

void bluetooth_server::deviceDiscovered(const QBluetoothDeviceInfo &device)
{

    emit DevicesList(device.name(),device.address().toString());
}

**Class B (UI)**

server = new bluetooth_server(this);

    connect(server, &bluetooth_server::DevicesList,
            this,  &bluetooth_settings::DevicesList)

void bluetooth_settings::DevicesList(const QString &name, const QString &address)
{
        ui->listWidget->addItem(name+"::"+address);
}

[J.Hilk]

@ahsan737
there you have it, you have to continue scanning after its finished

for example:

connect(agent, &QBluetoothDeviceDiscoveryAgent::finished, agent, &QBluetoothDeviceDiscoveryAgent::start);

make sure you compare the uuids, so that you don't add already discovered devices

[ahsan737]

@j-hilk oh thank you so much, I am very beginner so cannot even understand documentation sometimes. Can you please give a clue how to compare the UUIDs in order to avoid already discovered devices?

[J.Hilk]

@ahsan737
QBluetoothDeviceInfo has an access function deviceUuid save them in a QList and before adding simply parse through the list to check if the uuid was already added

[ahsan737]

@j-hilk got it, thanks. I am trying it. I still cannot understand one fact that whenever I turn off Bluetooth, enter the app and then turn on Bluetooth (using localdevice.poweron ()) then it always scans immediately.

[ahsan737]

@ahsan737 I cannot fix it on my device (Meizu X8) but I have tested the app on other device and scanner was working fine. So there is a chance this particular device is causing the problem.