Mryntu

I successfully added custom shipping method like this:

app/etc/config.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Store:etc/config.xsd">
 <default>
 <carriers>
 <lime>
 <active>1</active>
 <allowed_methods>delivery</allowed_methods>
 <methods>delivery</methods>
 <type>NAMESPACE</type>
 <sallowspecific>0</sallowspecific>
 <model>NamespaceModuleModelCarrier</model>
 <name>Namespace_Module custom Shipping</name>
 <title>Namespace_Module custom Shipping</title>
 <handling_type>F</handling_type>
 </lime>
 </carriers>
 </default>
</config>

app/code/Namespace/Module/Model/Carrier.php

public function collectRates(RateRequest $request)

 if (!$this->getConfigFlag('active')) 
 return false;
 
 $result = $this->_rateResultFactory->create(); 
 $method = $this->_rateMethodFactory->create(); 
 $method->setCarrier('HILO');
 $method->setCarrierTitle('HILO'); 
 $method->setMethod('Fast');
 $method->setMethodTitle('Fast'); 
 $amount = $this->getConfigData('price'); 
 $method->setPrice($amount);
 $method->setCost($amount); 
 $result->append($method);
 return $result;

It shows up at checkout page, but I want to show custom text area input data when the user choose my custom shipping method, and I can save the custom input text area data.

here's what I want it to look like:

In order to show a custom input field after selecting your custom shipping method, you have to add a js block subscribing to select method event:

Add a custom phtml to layout checkout_index_index.xml

Then add the next block to your phtml:

<script type="text/javascript">
 require([
 'jquery',
 'Magento_Checkout/js/model/quote',
 ], function (jQuery, quote) 
 jQuery(document).ready(function () 
 quote.shippingMethod.subscribe(function (value) 
 if (quote.shippingMethod() && quote.shippingMethod().carrier_code == 'your_custom_shipping_method_code') 
 var customBlock = "<div class ='custom-information'><input type="text" id="your_custom_id"></div>";
 if((!$('.custom-information').length > 0)) 
 $('#checkout-shipping-method-load').append(customBlock);
 
 );
 );
 );
 );
</script>

With the above code, you will add the input you want below your custom shipping method.

After that, you should have to create a plugin to save your custom value.

Check: MagentoCheckoutModelGuestShippingInformationManagement

I hope it helps you.
Regards,
Pablo