Enable/disable an input field Based on Picklist Value

Controller Code :-

public class Sampletest
{
    public String State {get;set;}
    public String District{get;set;}
    public Boolean StateBool {get;set;}
    
    public sampletest()
    {        
        State  = 'none';
        if(State == 'none')
        {
         StateBool = true;
        }    
    }
    
    public void StateBool()
    {        
        if(State != 'none')
        {
            StateBool = false;
        }
        else
        {
            StateBool = true; 
        } 
    }
       
}

Visualforce Page :-

<apex:page controller="Sampletest">
<apex:form >
<apex:actionFunction name="changeBoolCall" action="{!StateBool}"/>
    <apex:pageblock id="pg">
        <apex:pageblockSection >
            <apex:pageblockSectionItem >
                Select State :-
            </apex:pageblockSectionItem>
            <apex:pageblockSectionItem >
               <apex:selectList value="{!State}" size="1" multiselect="false">
                   <apex:selectOption itemLabel="--- None ---" itemValue="none"/>
                   <apex:selectOption itemLabel="Karnataka" itemValue="inr"/>
                   <apex:selectOption itemLabel="Rajasthan" itemValue="inr"/>
                   <apex:actionSupport event="onchange" action="{!StateBool}" reRender="pg"/>
               </apex:selectList>
            </apex:pageblockSectionItem>            
            <apex:pageblockSectionItem >
                Enter the District:-
            </apex:pageblockSectionItem>      
            <apex:pageblockSectionItem >
               <apex:inputtext value="{!District}" disabled="{!StateBool}"/>
            </apex:pageblockSectionItem>                   
        </apex:pageblockSection>
    </apex:pageblock>
</apex:form>    
</apex:page>

Screenshot 1 :-

Screenshot 2:-