Magento 2.1.8 - Custom Online shipping module not displaying shipping methods on checkout

Question

I am creating a custom shipping module for magento 2.1.8.

I read on another post that shipping carriers divided into two types: online and offline shipping. (see How to programmaticlly create custom shipping method for third party API)

I seem to be having a problem with getting the shipping methods to display on the checkout with online shipping. The reason i want to use online shipping is because i need to create a shipping label in the admin panel when shipping the order, this functionality doesnt seem to be available with offline shipping.

I have tested the following code and the offline shipping code shows shipping methods on Checkout

Offline Shpping

use Magento\Shipping\Model\Carrier\AbstractCarrier;

class Carrier extends AbstractCarrier implements 
\Magento\Shipping\Model\Carrier\CarrierInterface
{
   /**
    * Collect and get rates
    *
    * @param RateRequest $request
    *
    * @return bool|Result
    */
   public function collectRates(RateRequest $request)
   {
       /** @var \Magento\Shipping\Model\Rate\Result $result */
       $result = $this->_rateResultFactory->create();

       /** @var \Magento\Quote\Model\Quote\Address\RateResult\Method $method */
       $method = $this->_shippingRateMethodFactory->create();

       $method->setCarrier($this->_code);
       $method->setCarrierTitle($this->_title);

       $method->setMethod("Shipper");
       $method->setMethodTitle("My Shipping Method");

       $amount = 120;

       $method->setPrice($amount);
       $method->setCost($amount);

       $result->append($method);

       return $result;
    }
}

The following online shipping code doesnt show shipping methods on checkout

Online Shipping

use Magento\Shipping\Model\Carrier\AbstractCarrierOnline;

class Carrier extends AbstractCarrierOnline
implements \Magento\Shipping\Model\Carrier\CarrierInterface
{
   /**
    * Collect and get rates
    *
    * @param RateRequest $request
    *
    * @return bool|Result
    */
   public function collectRates(RateRequest $request)
   {
       /** @var \Magento\Shipping\Model\Rate\Result $result */
       $result = $this->_rateResultFactory->create();

       /** @var \Magento\Quote\Model\Quote\Address\RateResult\Method $method */
       $method = $this->_shippingRateMethodFactory->create();

       $method->setCarrier($this->_code);
       $method->setCarrierTitle($this->_title);

       $method->setMethod("Shipper");
       $method->setMethodTitle("My Shipping Method");

       $amount = 120;

       $method->setPrice($amount);
       $method->setCost($amount);

       $result->append($method);

       return $result;
    }
}

My problem is why is the shipping methods not displaying on checkout when i use the online shipping method code but it works fine with the offline code?

can someone hint me or guide in the right direction? Thanks

Answer 1

add this method in your class.

public function proccessAdditionalValidation(\Magento\Framework\DataObject $request) {
        return true;
    }

Answer 2

If you are creating online shipping module the add below to your config.xml file and issue will be solved.

<max_package_weight>70</max_package_weight>