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When the activity is opened on a phone with API < 18 it gives the exception 

Could not find class 'android.bluetooth.BluetoothManager'

Despite the following check:

private void activateBluetoothSmart() {

    if (getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE) && (Build.VERSION.SDK_INT >= 18)) {
        final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        myBluetoothAdapter = bluetoothManager.getAdapter();

        if (myBluetoothAdapter == null || myBluetoothAdapter.isEnabled() == false) {
            Intent enableBluetoothIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBluetoothIntent, REQUEST_ENABLE_BT);
        } else {
            scanForHrm();
        }
    }
}

Apart from why the version check is being ignored I don't understand why the code is being called when the activity is opened, it should only be called when the user presses a button.

Are all classes 'preloaded' when an activity is opened? I've looked at this question: NoClassDefFoundError during class load for BLE scanning callback which suggests the version code check as well as the feature check but haven't found anything else.

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user1977132
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1 Answers1

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So the problem is that all referenced classes are imported when the activity is opened. The solution was to create a new class and to place all the Bluetooth LE related code within that new class and then call methods of that new class with the correct condition checks.

I think this works because of "lazy class loading", the referenced classes are now within a new class and they only get imported when that class is called.

user1977132
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  • I've answered the question with what ended up working for me, I'm aware the answer is inadequate but thought somebody might find something better than nothing! – user1977132 Feb 07 '16 at 11:10