public class WorkBenchControllerClass {
     public String obj;
    public List<String> objFields {get;set;}
    
    public WorkBenchControllerClass() 
    {    
    }
    public String getobj()
    {
        return obj;
    }
     public void setobj(String obj)
    {
        this.obj = obj;
    } 
    
//Fetching Sobjects
public List<SelectOption> getobjectnames()
{
    Map <String, Schema.SObjectType> schemaMap = Schema.getGlobalDescribe();
    System.debug('globaldesc values--> '+schemaMap);
    List<SelectOption> options=new List<SelectOption>();
    options.add(new SelectOption('None','None'));
    for(Schema.SObjectType objType : schemaMap.values())
    {
    options.add(new SelectOption(objType.getDescribe().getName(),objType.getDescribe().getName()));
    }
    return options;
}
 
//Fetching Fields
 public List<SelectOption> fetchFields()
    { 
        List<SelectOption> allfields=new List<SelectOption>();
        List<String> fields = new List<String>();
        Map<String , Schema.SObjectType> globalDescription = Schema.getGlobalDescribe();
        System.debug('Selected Object is ' + obj);
        Schema.sObjectType objType = globalDescription.get(obj); 
        System.debug('Object Type is ' + objType);
        Schema.DescribeSObjectResult r1 = objType.getDescribe(); 
        
        Map<String , Schema.SObjectField> mapFieldList = r1.fields.getMap();  

        for(Schema.SObjectField field : mapFieldList.values())  
        {  
            Schema.DescribeFieldResult fieldResult = field.getDescribe();  
            
            if(fieldResult.isAccessible())  
            {  
                System.debug('Field Name is ' + fieldResult.getName());
                //fields.add(fieldResult.getName());
                allfields.add(new SelectOption(fieldResult.getName(),fieldResult.getName()));
            }  
        }
        return allfields;
             
    }   
}
I Tried PageReference also but its not working because.it should return list of fields.
Please Help Me to fix this error