Remove unsupported Android bluetooth codepaths

Minimum Android level supported on Qt 6 is Android 6 / API Level 23.
This commit removes older unsupported code in order to simplify.

This concerns primarily:
- sdkVersion() checks
- Java reflections (API availability was uncertain)

Task-number: QTBUG-102497
Change-Id: Ia90248a0a8f8e32130b8394998c2676c97a02eb5
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
(cherry picked from commit bb419a4c608b94ff311e1609306f5f0fbc59d3cf)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

13 files changed, 59 insertions, 272 deletions

diff --git a/examples/bluetooth/btchat/chat.cpp b/examples/bluetooth/btchat/chat.cpp
index 7fb84ca0..51723813 100644
--- a/examples/bluetooth/btchat/chat.cpp
+++ b/examples/bluetooth/btchat/chat.cpp
@@ -200,10 +200,9 @@ void Chat::connectClicked()
 
     RemoteSelector remoteSelector(adapter);
 #ifdef Q_OS_ANDROID
-    if (QNativeInterface::QAndroidApplication::sdkVersion() >= 23)
-        remoteSelector.startDiscovery(QBluetoothUuid(reverseUuid));
-    else
-        remoteSelector.startDiscovery(QBluetoothUuid(serviceUuid));
+    // QTBUG-61392
+    Q_UNUSED(serviceUuid);
+    remoteSelector.startDiscovery(QBluetoothUuid(reverseUuid));
 #else
     remoteSelector.startDiscovery(QBluetoothUuid(serviceUuid));
 #endif
diff --git a/examples/bluetooth/pingpong/pingpong.cpp b/examples/bluetooth/pingpong/pingpong.cpp
index 8053fe4e..f3ee70a4 100644
--- a/examples/bluetooth/pingpong/pingpong.cpp
+++ b/examples/bluetooth/pingpong/pingpong.cpp
@@ -291,11 +291,9 @@ void PingPong::startClient()
             this, &PingPong::done);
     connect(discoveryAgent, &QBluetoothServiceDiscoveryAgent::errorOccurred, this,
             &PingPong::serviceScanError);
-#ifdef Q_OS_ANDROID //see QTBUG-61392
-    if (QNativeInterface::QAndroidApplication::sdkVersion() >= 23)
-        discoveryAgent->setUuidFilter(QBluetoothUuid(androidUuid));
-    else
-        discoveryAgent->setUuidFilter(QBluetoothUuid(serviceUuid));
+#ifdef Q_OS_ANDROID
+    // QTBUG-61392
+    discoveryAgent->setUuidFilter(QBluetoothUuid(androidUuid));
 #else
     discoveryAgent->setUuidFilter(QBluetoothUuid(serviceUuid));
 #endif
diff --git a/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothBroadcastReceiver.java b/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothBroadcastReceiver.java
index b709e8e5..c96e2b69 100644
--- a/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothBroadcastReceiver.java
+++ b/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothBroadcastReceiver.java
@@ -43,13 +43,15 @@ package org.qtproject.qt.android.bluetooth;
 import android.app.Activity;
 import android.bluetooth.BluetoothAdapter;
 import android.bluetooth.BluetoothDevice;
+import android.bluetooth.BluetoothProfile;
+import android.bluetooth.BluetoothManager;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.util.Log;
 
-import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.lang.reflect.Field;
 import java.util.HashSet;
 import java.util.List;
 
@@ -157,6 +159,7 @@ public class QtBluetoothBroadcastReceiver extends BroadcastReceiver
     static public boolean setPairingMode(String address, boolean isPairing)
     {
         BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
+        // Uses reflection as the removeBond() is not part of public API
         try {
             BluetoothDevice device = adapter.getRemoteDevice(address);
             String methodName = "createBond";
diff --git a/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLE.java b/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLE.java
index b4a41307..17611210 100644
--- a/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLE.java
+++ b/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLE.java
@@ -102,7 +102,6 @@ public class QtBluetoothLE {
     private final int RUNNABLE_TIMEOUT = 3000; // 3 seconds
     private final Handler timeoutHandler = new Handler(Looper.getMainLooper());
 
-    /* New BTLE scanner setup since Android SDK v21 */
     private BluetoothLeScanner mBluetoothLeScanner = null;
 
     private class TimeoutRunnable implements Runnable {
@@ -223,18 +222,19 @@ public class QtBluetoothLE {
             return true;
 
         if (isEnabled) {
-            Log.d(TAG, "New BTLE scanning API");
+            Log.d(TAG, "Attempting to start BTLE scan");
             ScanSettings.Builder settingsBuilder = new ScanSettings.Builder();
             settingsBuilder = settingsBuilder.setScanMode(ScanSettings.SCAN_MODE_BALANCED);
             ScanSettings settings = settingsBuilder.build();
 
             List<ScanFilter> filterList = new ArrayList<ScanFilter>();
 
-            mBluetoothLeScanner.startScan(filterList, settings, leScanCallback21);
+            mBluetoothLeScanner.startScan(filterList, settings, leScanCallback);
             mLeScanRunning = true;
         } else {
+            Log.d(TAG, "Attempting to stop BTLE scan");
             try {
-                mBluetoothLeScanner.stopScan(leScanCallback21);
+                mBluetoothLeScanner.stopScan(leScanCallback);
             } catch (IllegalStateException isex) {
                 // when trying to stop a scan while bluetooth is offline
                 // java.lang.IllegalStateException: BT Adapter is not turned ON
@@ -246,8 +246,7 @@ public class QtBluetoothLE {
         return (mLeScanRunning == isEnabled);
     }
 
-    // Device scan callback (SDK v21+)
-    private final ScanCallback leScanCallback21 = new ScanCallback() {
+    private final ScanCallback leScanCallback = new ScanCallback() {
         @Override
         public void onScanResult(int callbackType, ScanResult result) {
             super.onScanResult(callbackType, result);
@@ -688,7 +687,7 @@ public class QtBluetoothLE {
             super.onDescriptorWrite(gatt, descriptor, status);
             handleOnDescriptorWrite(gatt, descriptor, status);
         }
-        //TODO Requires Android API 21 which is not available on CI yet.
+        //TODO currently not supported
 //        public void onReliableWriteCompleted(android.bluetooth.BluetoothGatt gatt,
 //                                             int status) {
 //            System.out.println("onReliableWriteCompleted");
@@ -699,7 +698,6 @@ public class QtBluetoothLE {
 //            System.out.println("onReadRemoteRssi");
 //        }
 
-        // requires Android API v21
         public void onMtuChanged(android.bluetooth.BluetoothGatt gatt, int mtu, int status)
         {
             super.onMtuChanged(gatt, mtu, status);
@@ -763,7 +761,7 @@ public class QtBluetoothLE {
 
         if (mBluetoothGatt == null) {
             try {
-                //This API element is currently: greylist-max-o, reflection, allowed
+                //This API element is currently: greylist-max-o (API level 27), reflection, allowed
                 //It may change in the future
                 Class[] constr_args = new Class[5];
                 constr_args[0] = android.bluetooth.BluetoothGattService.class;
@@ -781,34 +779,15 @@ public class QtBluetoothLE {
                     Nevertheless we continue with best effort.
                 */
             }
-
             try {
-                // BluetoothDevice.connectGatt(Context, boolean, BluetoothGattCallback, int) was
-                // officially introduced by Android API v23. Earlier Android versions have a
-                // private
-                // implementation already though. Let's check at runtime and use it if possible.
-                //
-                // In general the new connectGatt() seems to be much more reliable than the
-                // function
-                // that doesn't specify the transport layer.
-
-                Class[] args = new Class[4];
-                args[0] = android.content.Context.class;
-                args[1] = boolean.class;
-                args[2] = android.bluetooth.BluetoothGattCallback.class;
-                args[3] = int.class;
-                Method connectMethod = mRemoteGattDevice.getClass().getDeclaredMethod("connectGatt", args);
-                if (connectMethod != null) {
-                    mBluetoothGatt = (BluetoothGatt) connectMethod.invoke(mRemoteGattDevice, qtContext, false,
-                            gattCallback, 2 /* TRANSPORT_LE */);
-                    Log.w(TAG, "Using Android v23 BluetoothDevice.connectGatt()");
-                }
-            } catch (Exception ex) {
-                // fallback to less reliable API 18 version
-                mBluetoothGatt = mRemoteGattDevice.connectGatt(qtContext, false, gattCallback);
+                mBluetoothGatt =
+                    mRemoteGattDevice.connectGatt(qtContext, false,
+                                                  gattCallback, 2 /* TRANSPORT_LE */);
+            } catch (IllegalArgumentException ex) {
+                Log.w(TAG, "Gatt connection failed");
+                ex.printStackTrace();
             }
         }
-
         return mBluetoothGatt != null;
     }
 
@@ -1136,26 +1115,18 @@ public class QtBluetoothLE {
                 handleDiscoveredService + 1, discoveredService.endHandle + 1);
     }
 
-    // Executes under "this" client mutex
+    // Executes under "this" client mutex. Returns true
+    // if no actual MTU exchange is initiated
     private boolean executeMtuExchange()
     {
-        if (Build.VERSION.SDK_INT >= 21) {
-            try {
-                Method mtuMethod = mBluetoothGatt.getClass().getDeclaredMethod("requestMtu", int.class);
-                if (mtuMethod != null) {
-                    Boolean success = (Boolean) mtuMethod.invoke(mBluetoothGatt, MAX_MTU);
-                    if (success.booleanValue()) {
-                        Log.w(TAG, "MTU change initiated");
-                        return false;
-                    } else {
-                        Log.w(TAG, "MTU change request failed");
-                    }
-                }
-            } catch (Exception ex) {}
+        if (mBluetoothGatt.requestMtu(MAX_MTU)) {
+            Log.w(TAG, "MTU change initiated");
+            return false;
+        } else {
+            Log.w(TAG, "MTU change request failed");
         }
 
-       Log.w(TAG, "Assuming default MTU value of 23 bytes");
-
+        Log.w(TAG, "Assuming default MTU value of 23 bytes");
         mSupportedMtu = DEFAULT_MTU;
         return true;
     }
@@ -1723,22 +1694,16 @@ public class QtBluetoothLE {
         if (mBluetoothGatt == null)
             return false;
 
-        try {
-            //Android API v21
-            Method connectionUpdateMethod = mBluetoothGatt.getClass().getDeclaredMethod(
-                                                "requestConnectionPriority", int.class);
-            if (connectionUpdateMethod == null)
-                return false;
-
-            int requestPriority = 0; // BluetoothGatt.CONNECTION_PRIORITY_BALANCED
-            if (minimalInterval < 30)
-                requestPriority = 1; // BluetoothGatt.CONNECTION_PRIORITY_HIGH
-            else if (minimalInterval > 100)
-                requestPriority = 2; //BluetoothGatt/CONNECTION_PRIORITY_LOW_POWER
+        int requestPriority = 0; // BluetoothGatt.CONNECTION_PRIORITY_BALANCED
+        if (minimalInterval < 30)
+            requestPriority = 1; // BluetoothGatt.CONNECTION_PRIORITY_HIGH
+        else if (minimalInterval > 100)
+            requestPriority = 2; //BluetoothGatt.CONNECTION_PRIORITY_LOW_POWER
 
-            Object result = connectionUpdateMethod.invoke(mBluetoothGatt, requestPriority);
-            return (Boolean) result;
-        } catch (Exception ex) {
+        try {
+            return mBluetoothGatt.requestConnectionPriority(requestPriority);
+        } catch (IllegalArgumentException ex) {
+            Log.w(TAG, "Connection update priority out of range: " + requestPriority);
             return false;
         }
     }
diff --git a/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp b/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp
index 1fec7f81..caaabadf 100644
--- a/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp
+++ b/src/bluetooth/android/devicediscoverybroadcastreceiver.cpp
@@ -595,14 +595,10 @@ QBluetoothDeviceInfo DeviceDiscoveryBroadcastReceiver::retrieveDeviceInfo(const
         env->ReleaseByteArrayElements(scanRecord, elems, JNI_ABORT);
     }
 
-    if (QNativeInterface::QAndroidApplication::sdkVersion() >= 18) {
-        auto methodId = env.findMethod(bluetoothDevice.objectClass(),
-                                       "getType",
-                                       "()I");
-        jint javaBtType = env->CallIntMethod(bluetoothDevice.object(), methodId);
-        if (!env.checkAndClearExceptions()) {
-            info.setCoreConfigurations(qtBtTypeForJavaBtType(javaBtType));
-        }
+    auto methodId = env.findMethod(bluetoothDevice.objectClass(), "getType", "()I");
+    jint javaBtType = env->CallIntMethod(bluetoothDevice.object(), methodId);
+    if (!env.checkAndClearExceptions()) {
+        info.setCoreConfigurations(qtBtTypeForJavaBtType(javaBtType));
     }
 
     return info;
diff --git a/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp b/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp
index b1a6551e..a23de9d7 100644
--- a/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp
+++ b/src/bluetooth/android/servicediscoverybroadcastreceiver.cpp
@@ -51,8 +51,7 @@ Q_DECLARE_LOGGING_CATEGORY(QT_BT_ANDROID)
 
 ServiceDiscoveryBroadcastReceiver::ServiceDiscoveryBroadcastReceiver(QObject* parent): AndroidBroadcastReceiver(parent)
 {
-    if (QNativeInterface::QAndroidApplication::sdkVersion() >= 15)
-        addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionUuid)); //API 15+
+    addAction(valueForStaticField(JavaNames::BluetoothDevice, JavaNames::ActionUuid));
 }
 
 void ServiceDiscoveryBroadcastReceiver::onReceive(JNIEnv *env, jobject context, jobject intent)
diff --git a/src/bluetooth/qbluetoothdevicediscoveryagent_android.cpp b/src/bluetooth/qbluetoothdevicediscoveryagent_android.cpp
index 6b6cfa20..f1569266 100644
--- a/src/bluetooth/qbluetoothdevicediscoveryagent_android.cpp
+++ b/src/bluetooth/qbluetoothdevicediscoveryagent_android.cpp
@@ -235,18 +235,6 @@ void QBluetoothDeviceDiscoveryAgentPrivate::start(QBluetoothDeviceDiscoveryAgent
     if (requestedMethods & QBluetoothDeviceDiscoveryAgent::LowEnergyMethod) {
         // LE search only requested or classic discovery failed but lets try LE scan anyway
         Q_ASSERT(requestedMethods & QBluetoothDeviceDiscoveryAgent::LowEnergyMethod);
-
-        if (QNativeInterface::QAndroidApplication::sdkVersion() < 18) {
-            qCDebug(QT_BT_ANDROID) << "Skipping Bluetooth Low Energy device scan due to "
-                                      "insufficient Android version"
-                                     << QNativeInterface::QAndroidApplication::sdkVersion();
-            m_active = NoScanActive;
-            lastError = QBluetoothDeviceDiscoveryAgent::UnsupportedDiscoveryMethod;
-            errorString = QBluetoothDeviceDiscoveryAgent::tr("Low Energy Discovery not supported");
-            emit q->errorOccurred(lastError);
-            return;
-        }
-
         startLowEnergyScan();
     }
 }
@@ -311,14 +299,7 @@ void QBluetoothDeviceDiscoveryAgentPrivate::processSdpDiscoveryFinished()
             return;
         }
 
-        // start LE scan if supported
-        if (QNativeInterface::QAndroidApplication::sdkVersion() < 18) {
-            qCDebug(QT_BT_ANDROID) << "Skipping Bluetooth Low Energy device scan";
-            m_active = NoScanActive;
-            emit q->finished();
-        } else {
-            startLowEnergyScan();
-        }
+        startLowEnergyScan();
     }
 }
 
diff --git a/src/bluetooth/qbluetoothlocaldevice_android.cpp b/src/bluetooth/qbluetoothlocaldevice_android.cpp
index 8c40ab62..4afae162 100644
--- a/src/bluetooth/qbluetoothlocaldevice_android.cpp
+++ b/src/bluetooth/qbluetoothlocaldevice_android.cpp
@@ -379,9 +379,8 @@ void QBluetoothLocalDevice::requestPairing(const QBluetoothAddress &address, Pai
         return;
     }
 
-    // BluetoothDevice::createBond() requires Android API 15
-    if (QNativeInterface::QAndroidApplication::sdkVersion() < 15 || !d_ptr->adapter()) {
-        qCWarning(QT_BT_ANDROID) <<  "Unable to pair: requires Android API 15+";
+    if (!d_ptr->adapter()) {
+        qCWarning(QT_BT_ANDROID) <<  "Unable to pair, invalid adapter";
         QMetaObject::invokeMethod(this, "errorOccurred", Qt::QueuedConnection,
                                   Q_ARG(QBluetoothLocalDevice::Error,
                                         QBluetoothLocalDevice::PairingError));
diff --git a/src/bluetooth/qbluetoothservicediscoveryagent_android.cpp b/src/bluetooth/qbluetoothservicediscoveryagent_android.cpp
index 48b09eff..5b9d1965 100644
--- a/src/bluetooth/qbluetoothservicediscoveryagent_android.cpp
+++ b/src/bluetooth/qbluetoothservicediscoveryagent_android.cpp
@@ -86,13 +86,6 @@ QBluetoothServiceDiscoveryAgentPrivate::QBluetoothServiceDiscoveryAgentPrivate(
         }
     }
 
-    if (QNativeInterface::QAndroidApplication::sdkVersion() < 15)
-        qCWarning(QT_BT_ANDROID)
-            << "SDP not supported by Android API below version 15. Detected version: "
-            << QNativeInterface::QAndroidApplication::sdkVersion()
-            << "Service discovery will return empty list.";
-
-
     /*
       We assume that the current local adapter has been passed.
       The logic below must change once there is more than one adapter.
@@ -152,29 +145,6 @@ void QBluetoothServiceDiscoveryAgentPrivate::start(const QBluetoothAddress &addr
         return;
     }
 
-    /* SDP discovery was officially added by Android API v15
-     * BluetoothDevice.getUuids() existed in earlier APIs already and in the future we may use
-     * reflection to support earlier Android versions than 15. Unfortunately
-     * BluetoothDevice.fetchUuidsWithSdp() and related APIs had some structure changes
-     * over time. Therefore we won't attempt this with reflection.
-     *
-     * TODO: Use reflection to support getUuuids() where possible.
-     * */
-    if (QNativeInterface::QAndroidApplication::sdkVersion() < 15) {
-        qCWarning(QT_BT_ANDROID) << "Aborting SDP enquiry due to too low Android API version (requires v15+)";
-
-        error = QBluetoothServiceDiscoveryAgent::UnknownError;
-        errorString = QBluetoothServiceDiscoveryAgent::tr("Android API below v15 does not support SDP discovery");
-
-        //abort any outstanding discoveries
-        sdpCache.clear();
-        discoveredDevices.clear();
-        emit q->errorOccurred(error);
-        _q_serviceDiscoveryFinished();
-
-        return;
-    }
-
     QJniObject inputString = QJniObject::fromString(address.toString());
     QJniObject remoteDevice =
             btAdapter.callObjectMethod("getRemoteDevice",
diff --git a/src/bluetooth/qbluetoothsocket_android.cpp b/src/bluetooth/qbluetoothsocket_android.cpp
index 40969e8b..36fddf2c 100644
--- a/src/bluetooth/qbluetoothsocket_android.cpp
+++ b/src/bluetooth/qbluetoothsocket_android.cpp
@@ -54,7 +54,6 @@ QT_BEGIN_NAMESPACE
 
 Q_DECLARE_LOGGING_CATEGORY(QT_BT_ANDROID)
 
-#define FALLBACK_CHANNEL 1
 #define USE_FALLBACK true
 
 Q_DECLARE_METATYPE(QJniObject)
@@ -200,104 +199,9 @@ bool QBluetoothSocketPrivateAndroid::ensureNativeSocket(QBluetoothServiceInfo::P
     return false;
 }
 
-bool QBluetoothSocketPrivateAndroid::fallBackConnect(QJniObject uuid, int channel)
-{
-    qCWarning(QT_BT_ANDROID) << "Falling back to getServiceChannel() workaround.";
-
-    QJniEnvironment env;
-
-    QJniObject remoteDeviceClass = remoteDevice.callObjectMethod("getClass", "()Ljava/lang/Class;");
-    if (!remoteDeviceClass.isValid()) {
-        qCWarning(QT_BT_ANDROID) << "Could not invoke BluetoothDevice.getClass.";
-        return false;
-    }
-
-    QJniObject integerObject = QJniObject::getStaticObjectField(
-                                            "java/lang/Integer", "TYPE", "Ljava/lang/Class;");
-    if (!integerObject.isValid()) {
-        qCWarning(QT_BT_ANDROID) << "Could not get Integer.TYPE";
-        return false;
-    }
-
-    jclass classClass = env.findClass("java/lang/Class");
-    jobjectArray rawArray = env->NewObjectArray(1, classClass,
-                                                integerObject.object<jobject>());
-    QJniObject paramTypes(rawArray);
-    env->DeleteLocalRef(rawArray);
-    if (!paramTypes.isValid()) {
-        qCWarning(QT_BT_ANDROID) << "Could not create new Class[]{Integer.TYPE}";
-        return false;
-    }
-
-    QJniObject parcelUuid("android/os/ParcelUuid", "(Ljava/util/UUID;)V",
-                                 uuid.object());
-    if (parcelUuid.isValid()) {
-        auto methodId = env.findMethod(remoteDevice.objectClass(), "getServiceChannel",
-                                         "(Landroid/os/ParcelUuid;)I");
-        jint socketChannel = 0;
-        if (methodId) {
-            socketChannel = env->CallIntMethod(remoteDevice.object(), methodId, parcelUuid.object());
-            if (!env.checkAndClearExceptions()) {
-                if (socketChannel
-                    == remoteDevice.getStaticField<jint>("android/bluetooth/BluetoothDevice", "ERROR")
-                    || socketChannel == -1) {
-                    qCWarning(QT_BT_ANDROID) << "Cannot determine RFCOMM service channel.";
-                } else {
-                    qCWarning(QT_BT_ANDROID) << "Using found rfcomm channel" << socketChannel;
-                    channel = socketChannel;
-                }
-            }
-        }
-    }
-    QJniObject method;
-    if (secFlags == QBluetooth::SecurityFlags(QBluetooth::Security::NoSecurity)) {
-        qCDebug(QT_BT_ANDROID) << "Connnecting via insecure rfcomm";
-        method = remoteDeviceClass.callObjectMethod(
-                "getMethod",
-                "(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;",
-                QJniObject::fromString(QLatin1String("createInsecureRfcommSocket")).object<jstring>(),
-                paramTypes.object<jobjectArray>());
-    } else {
-        qCDebug(QT_BT_ANDROID) << "Connnecting via secure rfcomm";
-        method = remoteDeviceClass.callObjectMethod(
-                "getMethod",
-                "(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;",
-                QJniObject::fromString(QLatin1String("createRfcommSocket")).object<jstring>(),
-                paramTypes.object<jobjectArray>());
-    }
-    if (!method.isValid()) {
-        qCWarning(QT_BT_ANDROID) << "Could not invoke getMethod";
-        return false;
-    }
-
-    jclass objectClass = env.findClass("java/lang/Object");
-    QJniObject channelObject = QJniObject::callStaticObjectMethod(
-                                        "java/lang/Integer", "valueOf", "(I)Ljava/lang/Integer;", channel);
-    rawArray = env->NewObjectArray(1, objectClass, channelObject.object<jobject>());
-
-    QJniObject invokeResult = method.callObjectMethod("invoke",
-                                         "(Ljava/lang/Object;[Ljava/lang/Object;)Ljava/lang/Object;",
-                                         remoteDevice.object<jobject>(), rawArray);
-    env->DeleteLocalRef(rawArray);
-    if (!invokeResult.isValid())
-    {
-        qCWarning(QT_BT_ANDROID) << "Invoke Resulted with error.";
-        return false;
-    }
-
-    socketObject = QJniObject(invokeResult);
-
-    WorkerThread *workerThread = new WorkerThread();
-    workerThread->setupWorker(this, socketObject, uuid, USE_FALLBACK);
-    workerThread->start();
-    emit connectJavaSocket();
-
-    qCWarning(QT_BT_ANDROID) << "Workaround thread invoked.";
-    return true;
-}
-
 /*
- * Workaround for QTBUG-61392
+ * Workaround for QTBUG-61392. If the underlying Android bug gets fixed,
+ * we need to consider restoring the non-reversed fallbackConnect from the repository.
  */
 bool QBluetoothSocketPrivateAndroid::fallBackReversedConnect(const QBluetoothUuid &uuid)
 {
@@ -353,14 +257,13 @@ bool QBluetoothSocketPrivateAndroid::fallBackReversedConnect(const QBluetoothUui
  * 3. if threaded connect succeeds call socketConnectSuccess() via signals
  *      -> done
  * 4. if threaded connect fails call defaultSocketConnectFailed() via signals
- * 5. call fallBackConnect() if Android version 22 or below
- *     -> Android 23+ complete failure of entire connectToServiceHelper()
- * 6. call fallBackReversedConnect() if Android version 23 or above
+ * 5. call fallBackReversedConnect()
  *     -> if failure entire connectToServiceHelper() fails
- * 7. if threaded connect on one of above fallbacks succeeds call socketConnectSuccess()
+ *     Note: This fallback can be disabled with private API boolean
+ * 6. if threaded connect on one of above fallbacks succeeds call socketConnectSuccess()
  *    via signals
  *      -> done
- * 8. if threaded connect on fallback channel fails call fallbackSocketConnectFailed()
+ * 7. if threaded connect on fallback channel fails call fallbackSocketConnectFailed()
  *      -> complete failure of entire connectToServiceHelper()
  * */
 void QBluetoothSocketPrivateAndroid::connectToServiceHelper(const QBluetoothAddress &address,
@@ -599,6 +502,7 @@ void QBluetoothSocketPrivateAndroid::defaultSocketConnectFailed(
         const QJniObject &socket, const QJniObject &targetUuid,
         const QBluetoothUuid &qtTargetUuid)
 {
+    Q_UNUSED(targetUuid);
     Q_Q(QBluetoothSocket);
 
     // test we didn't get a fail from a previous connect
@@ -606,18 +510,12 @@ void QBluetoothSocketPrivateAndroid::defaultSocketConnectFailed(
     if (socket != socketObject)
         return;
 
-    bool success = false;
-    if (QNativeInterface::QAndroidApplication::sdkVersion() <= 22)
-        success = fallBackConnect(targetUuid, FALLBACK_CHANNEL);
-    else if (useReverseUuidWorkAroundConnect) // version 23+ has Android bug (see QTBUG-61392)
-        success = fallBackReversedConnect(qtTargetUuid);
-
-    if (!success) {
+    if (!useReverseUuidWorkAroundConnect || !fallBackReversedConnect(qtTargetUuid)) {
         errorString = QBluetoothSocket::tr("Connection to service failed");
         socketObject = remoteDevice = QJniObject();
         q->setSocketError(QBluetoothSocket::SocketError::ServiceNotFoundError);
         q->setSocketState(QBluetoothSocket::SocketState::UnconnectedState);
-        qCWarning(QT_BT_ANDROID) << "Workaround failed";
+        qCWarning(QT_BT_ANDROID) << "Socket connect workaround failed";
     }
 }
 
@@ -918,9 +816,6 @@ qint64 QBluetoothSocketPrivateAndroid::bytesToWrite() const
  */
 QBluetoothUuid QBluetoothSocketPrivateAndroid::reverseUuid(const QBluetoothUuid &serviceUuid)
 {
-    if (QNativeInterface::QAndroidApplication::sdkVersion() < 23)
-        return serviceUuid;
-
     if (serviceUuid.isNull())
         return QBluetoothUuid();
 
diff --git a/src/bluetooth/qbluetoothsocket_android_p.h b/src/bluetooth/qbluetoothsocket_android_p.h
index ca1c4864..e1dc9270 100644
--- a/src/bluetooth/qbluetoothsocket_android_p.h
+++ b/src/bluetooth/qbluetoothsocket_android_p.h
@@ -81,7 +81,6 @@ public:
     void connectToService(const QBluetoothAddress &address, quint16 port,
                           QIODevice::OpenMode openMode) override;
 
-    bool fallBackConnect(QJniObject uuid, int channel);
     bool fallBackReversedConnect(const QBluetoothUuid &uuid);
 
     bool ensureNativeSocket(QBluetoothServiceInfo::Protocol type) override;
diff --git a/src/bluetooth/qlowenergycontroller_android.cpp b/src/bluetooth/qlowenergycontroller_android.cpp
index 17bab6f3..4ba7a7ce 100644
--- a/src/bluetooth/qlowenergycontroller_android.cpp
+++ b/src/bluetooth/qlowenergycontroller_android.cpp
@@ -92,20 +92,10 @@ QLowEnergyControllerPrivateAndroid::~QLowEnergyControllerPrivateAndroid()
 
 void QLowEnergyControllerPrivateAndroid::init()
 {
-    // Android Central/Client support starts with v18
-    // Peripheral/Server support requires Android API v21
     const bool isPeripheral = (role == QLowEnergyController::PeripheralRole);
-    const jint version = QNativeInterface::QAndroidApplication::sdkVersion();
 
     if (isPeripheral) {
-        if (version < 21) {
-            qWarning() << "Qt Bluetooth LE Peripheral support not available"
-                          "on Android devices below version 21";
-            return;
-        }
-
         qRegisterMetaType<QJniObject>();
-
         hub = new LowEnergyNotificationHub(remoteDevice, isPeripheral, this);
         // we only connect to the peripheral role specific signals
         // TODO add connections as they get added later on
@@ -120,12 +110,6 @@ void QLowEnergyControllerPrivateAndroid::init()
         connect(hub, &LowEnergyNotificationHub::serverDescriptorWritten,
                 this, &QLowEnergyControllerPrivateAndroid::serverDescriptorWritten);
     } else {
-        if (version < 18) {
-            qWarning() << "Qt Bluetooth LE Central/Client support not available"
-                          "on Android devices below version 18";
-            return;
-        }
-
         hub = new LowEnergyNotificationHub(remoteDevice, isPeripheral, this);
         // we only connect to the central role specific signals
         connect(hub, &LowEnergyNotificationHub::connectionUpdated,
@@ -1053,7 +1037,6 @@ void QLowEnergyControllerPrivateAndroid::stopAdvertising()
 
 void QLowEnergyControllerPrivateAndroid::requestConnectionUpdate(const QLowEnergyConnectionParameters &params)
 {
-    // Possible since Android v21
     // Android does not permit specification of specific latency or min/max
     // connection intervals (see BluetoothGatt.requestConnectionPriority()
     // In fact, each device manufacturer is permitted to change those values via a config
diff --git a/tests/bttestui/btlocaldevice.cpp b/tests/bttestui/btlocaldevice.cpp
index 2cb74e13..53634a78 100644
--- a/tests/bttestui/btlocaldevice.cpp
+++ b/tests/bttestui/btlocaldevice.cpp
@@ -315,8 +315,8 @@ void BtLocalDevice::serviceDiscovered(const QBluetoothServiceInfo &info)
     bool matchingService =
             (info.serviceUuid() == QBluetoothUuid(QString(TEST_SERVICE_UUID)));
 #ifdef Q_OS_ANDROID
-    if (QNativeInterface::QAndroidApplication::sdkVersion() >= 23) //bug introduced by Android 6.0.1
-        matchingService = matchingService
+    // QTBUG-61392
+    matchingService = matchingService
             || (info.serviceUuid() == QBluetoothUuid(QString(TEST_REVERSE_SERVICE_UUID)));
 #endif