Android Bluetooth Low Energy code compatible with API>=21 AND API<21

Question

I\'m developing an app that have to connect with a BLE device, in my code I want to use the new Scan and ScanCallback for BLE implemented from API 21 (Android 5) but I have

Answer 1

I would like to share my idea to overcome this crash on devices below API 21. The ScanCallback class has support from API 21. So when you write a code to implement ScanCallback in your scan code it will cause a crash on lover APIs. I have fixed it the following way:

I created one new abstract class which extending ScanCallback class as follows:

@TargetApi(Build.VERSION_CODES.LOLLIPOP)  
public abstract class AppScanCallback extends ScanCallback {}

Now I am using this class instance in my BluetoothService class as follow:

@RequiresApi(Build.VERSION_CODES.LOLLIPOP)
private AppScanCallback mScanCallback;

And using this variable as follow:

public void startBleScan() {
    if (isEnabled()) {
        if (Build.VERSION.SDK_INT < 21) {
            _bluetoothAdapter.startLeScan(mLeScanCallback);
        } else {
            mLEScanner = _bluetoothAdapter.getBluetoothLeScanner();
            settings = new ScanSettings.Builder()
                    .build();
            filters = new ArrayList<>();

            mScanCallback = new AppScanCallback() {
                @Override
                public void onScanResult(int callbackType, ScanResult result) {
                    if (Build.VERSION.SDK_INT >= 21) {
                        BluetoothDevice btDevice = result.getDevice();
                        onLeScanResult(btDevice, result.getScanRecord().getBytes());
                    }
                }

                @Override
                public void onBatchScanResults(List results) {
                    for (ScanResult sr : results) {
                        Log.i("ScanResult - Results", sr.toString());
                    }
                }
                @Override
                public void onScanFailed(int errorCode) {
                    Log.e("Scan Failed", "Error Code: " + errorCode);
                }
            };
            mLEScanner.startScan(filters, settings, mScanCallback);
        }

    }
}

and to stop scan

public void stopBLEScan() {;
        if (Build.VERSION.SDK_INT < 21) {
            _bluetoothAdapter.stopLeScan(mLeScanCallback);
        } else {
            mLEScanner.stopScan(mScanCallback);
        }
}

Hope it will help you out.