Programmatically turning on all notifications

Question

I am new to Android development and I can't understand how to properly turn all ble notifications and get all of them.

I've tried to loop through all services

for(BluetoothGattService service : gatt.getServices()){
            if( service.getUuid().equals(Step_UUID)) {
                BluetoothGattCharacteristic characteristicData = service.getCharacteristic(Step_UUID);
                for (BluetoothGattDescriptor descriptor : characteristicData.getDescriptors()) {
                    descriptor.setValue( BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
                    gatt.writeDescriptor(descriptor);
                }
                gatt.setCharacteristicNotification(characteristicData, true);
            }
        }

but I don't get any notifications back. Please, help I do not understand what I am doing wrong..

EDIT

Right now I use this method to enable notifications after services are discovered:

public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic, boolean enabled) {

        // Setting default write type according to CDT 222486
        characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);

        String serviceUUID = characteristic.getService().getUuid().toString();
        String serviceName = GattAttributes.lookupUUID(characteristic.getService().getUuid(), serviceUUID);

        String characteristicUUID = characteristic.getUuid().toString();
        String characteristicName = GattAttributes.lookupUUID(characteristic.getUuid(), characteristicUUID);

        String descriptorUUID = GattAttributes.CLIENT_CHARACTERISTIC_CONFIG;
        String descriptorName = GattAttributes.lookupUUID(UUIDDatabase.UUID_CLIENT_CHARACTERISTIC_CONFIG, descriptorUUID);

        if (characteristic.getDescriptor(UUID.fromString(GattAttributes.CLIENT_CHARACTERISTIC_CONFIG)) != null) {
            if (enabled == true) {
                BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID.fromString(GattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
                descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
                boolean aaa = mBluetoothGatt.writeDescriptor(descriptor);

                aaa = mBluetoothGatt.writeDescriptor(descriptor);
                aaa = false;
            } else {
                BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID.fromString(GattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
                descriptor.setValue(BluetoothGattDescriptor.DISABLE_NOTIFICATION_VALUE);
                mBluetoothGatt.writeDescriptor(descriptor);

            }
        }

        boolean aaaa = mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);
        aaaa = false;

    }

The problem is that first characteristic notifies well, but all others I am trying to enable fails on the line

mBluetoothGatt.writeDescriptor(descriptor);

Don't know what to do...

In your code you enable indications, but you said you wanted notifications? Also you can only have one outstanding GATT operation at a time (see your writeDescriptor calls). You need to wait for onDescriptorWrite before continuing. — Emil
You can only have one outstanding GATT operation at a time (see your writeDescriptor calls). You need to wait for onDescriptorWrite before continuing. If you don't do that, writeDescriptor will return false. — Emil

user3828374 user3828374 · Accepted Answer · 2019-03-19T14:48:34

My problem was resolved by overiding onDescriptorWrite method. I made a flag inside, and if it is true I continue to notify all left characteristics.

@Override public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) { String serviceUUID = descriptor.getCharacteristic().getService().getUuid().toString(); String serviceName = GattAttributes.lookupUUID(descriptor.getCharacteristic().getService().getUuid(), serviceUUID);

        String characteristicUUID = descriptor.getCharacteristic().getUuid().toString();
        String characteristicName = GattAttributes.lookupUUID(descriptor.getCharacteristic().getUuid(), characteristicUUID);

        String descriptorUUID = descriptor.getUuid().toString();
        String descriptorName = GattAttributes.lookupUUID(descriptor.getUuid(), descriptorUUID);

        if (status == BluetoothGatt.GATT_SUCCESS) {
            written = true;
            numberLeft--;
        } else {
            written = true;
            numberLeft--;
        }
    }

Programmatically turning on all notifications

1 Answers