Qt 6.2 Android Bluetooth Socket connect Error

[melaz123]

Hi I have a simple bluetooth app running on Android 9 that borrowed from a previous example with

void BluetoothClient::startClient(const QBluetoothServiceInfo &remoteService)
{
    if (socket)
        return;

    // Connect to service
    socket = new QBluetoothSocket(QBluetoothServiceInfo::RfcommProtocol);
    qDebug() << "Create socket";
    socket->connectToService(remoteService);
    qDebug() << "ConnectToService done";

    connect(socket, &QBluetoothSocket::readyRead,   this, &BluetoothClient::readSocket);
    connect(socket, &QBluetoothSocket::connected,   this, QOverload<>::of(&BluetoothClient::connected));
    connect(socket, &QBluetoothSocket::disconnected,this, &BluetoothClient::stopClient);
    connect(socket,&QBluetoothSocket::errorOccurred,this, &BluetoothClient::onSocketErrorOccurred);
    connect(this, &BluetoothClient::messageReceived,this, &BluetoothClient::onMessageRecieved );
}

However, every time I run I end up with the following errors and no connection to the Bluetooth module.

W System.err: java.lang.NoSuchMethodError: no non-static method "Landroid/bluetooth/BluetoothAdapter;.getRemoteDevice(Ljava/lang/String;)Landroid.bluetooth.BluetoothDevice;"
W System.err: 	at org.qtproject.qt.android.QtNative.startQtApplication(Native Method)
W System.err: 	at org.qtproject.qt.android.QtNative$7.run(QtNative.java:633)
W System.err: 	at org.qtproject.qt.android.QtThread$1.run(QtThread.java:61)
W System.err: 	at java.lang.Thread.run(Thread.java:764)

I have tried adding the following with no luck :

#include <QJniObject>
#include <QJniEnvironment>
#include <QCoreApplication>

#ifdef Q_OS_ANDROID
#include <QtCore/private/qandroidextras_p.h>
#endif

Any help is greatly appreciated.

[gregorykon]

Hi, I am new to Qt, but also have the same problem in connectToService (remote device is found but during connection I get the same exception). Just writing here in order not to double post. I thought maybe some build config might be wrong but no idea.

Any feedback would be helpful.

---

Windows 10 Home 10.0.19042
Openjdk, jdk-11.0.12.7-hotspot, javac 11.0.12, in Gradle JavaVersion.VERSION_11 (Hope this marginally complies with the documentation Note: 'JDK 11 or earlier must be used when using Qt for Android')
Android SDK Version 5.0, NDK Version 21.4.7075529, but project uses "21.3.6528147"

Project Settings for Testing:
Android_Qt_6_2_0_Clang_armeabi_v7a-Debug
Android Build SDK: android-30
Gradle 7.0.2
build-tools:30.0.3
qtMinSdkVersion=23
qtTargetSdkVersion=30

---

[melaz123]

Recently tried setting the missing COARSE LOCATION permissions by editing and creating a custom android manifest with the correct target api,

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

Both still with no luck.

The only way I seem to be able to get it to work is to switch build to:
Qt 5.15.2

I get some qml errors that cause designer to not be able to display my UI but when I connect to the service I no longer get the error and I can communicate properly. Seems like a Qt 6 issue for sure.

[gregorykon]

Thanks for the info, I also tried an older version (e.g. Qt 5.14.2) and communication seems to be working fine, but yes the problem remains for Qt 6.2.0

[russkij]

same problem with Qt 6.2.1

resolved in 6.2.3: https://bugreports.qt.io/browse/QTBUG-98353

[melaz123]

@russkij Thank you for the reply and pointing out a fix, from the debugging output and the bug ticket as you mentioned this should be the fix. I will double check with my Android versions and marked as solved!

[melaz123]

With the recent release of Qt 6.2.3 I verified that this has been fixed and android bluetooth is indeed working. Thanks everyone!