saveOpportunity : function(component,event,helper){
var action = component.get("c.getNewOppId");
action.setCallback(this, function(response){
    alert('Inside Callback method');
    if (state == "SUCCESS") {
        var optyId = response.getReturnValue();
        alert(optyId);
        var urlEvent = $A.get("e.force:navigateToURL");
        urlEvent.setParams({
            "url": "/006/o" + optyId
        });
        urlEvent.fire();
    }
});
$A.enqueueAction(action);

public pageReference saveOpp(){
    try{
        Id OpptyOwnerId = [SELECT Id FROM User WHERE Id =: userInfo.getUserId() and IsActive = True LIMIT 1].Id;
        system.debug('++OpptyOwnerId+'+OpptyOwnerId);
        Id RTId = [SELECT Id FROM RecordType WHERE sObjectType ='Opportunity' LIMIT 1].Id;
        Boolean isRegional = false;
        acc= NEW account();
        acc= [select name,id,Sales_Region__c from Account where id =:oppty.Accountid];
        if(oppty.SMB_OPP_Must_Win_level__c == null)oppty.SMB_OPP_Must_Win_level__c='None';
        if(isRegional )
        oppty.SMB_Opp_Must_Win__c = 'Yes';
        else
        oppty.SMB_Opp_Must_Win__c = 'No';
        oppty.OwnerId = OpptyOwnerId;

       if(REC.name == System.Label.OAB_Opportunity_Record_Type){
           oppty.StageName = '2 Qualification';
       }else{
           oppty.StageName = '1 Pre-qualification';
       }
         if(REC.name ==System.Label.OAB_Opportunity_Record_Type && acc.Sales_Region__c !='DEF'){
            system.debug('----------'+REC.name);
            ApexPages.addmessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'With a Simple DEF record type the account related to the opportunity must be a DEF account.'));
            return null;
        }

         if(REC.name ==System.Label.OAB_Opportunity_Record_Type && (oppty.Order_Type__c =='New Customer' || oppty.Order_Type__c =='New Business/GET')){
              oppty.Contract_Type__c= 'New';
        }else if(REC.name ==System.Label.OAB_Opportunity_Record_Type &&(oppty.Order_Type__c =='Renewal/KEEP' || oppty.Order_Type__c =='Organic/KEEP')){
                   oppty.Contract_Type__c= 'Existing';
        }

        insert oppty;

        //partner management evolution
        if(REC.name == System.Label.OAB_Opportunity_Record_Type){
            SMB_Partner__c insertNoPartner = new SMB_Partner__c(SMB_Opportunity__c=oppty.Id,
                                                                SMB_Name__c=Label.SMB_CL001_No_Partner_ID,
                                                               SMB_Amount__c=0,SMB_Percentage__c=0,
                                                               SMB_Primary__c=true);
            insert insertNoPartner;
        }
        //assign a contact to a new opportunity
        if(conId!=null){
            OpportunityContactRole oppContact = new OpportunityContactRole(ContactId=conId,IsPrimary=true,
                                                                           OpportunityId=oppty.Id,Role=Label.Contact_Role);
            insert oppContact;
        }
        PageReference pageRef = new PageReference('/' + oppty.Id + '?retURL=%2F' + oppty.Id);
           return pageRef;

    }
    catch(exception ex){
       if(!ex.getMessage().contains('FIELD_CUSTOM_VALIDATION_EXCEPTION'))
       Apexpages.addMessage(new Apexpages.Message(ApexPages.severity.ERROR, 'Exception Error: ' + ex));
        return null;
    }
     return null;
}

public PageReference saveOpp(){
    Id returnedId = getNewOppId();
    return new PageReference('/'+returnedId);
}

 // Method to get the opportunity Id
@AuraEnabled
public static Id getNewOppId(){
    try{
        Id OpptyOwnerId = [SELECT Id FROM User WHERE Id =: userInfo.getUserId() and IsActive = True LIMIT 1].Id;
        system.debug('++OpptyOwnerId+'+OpptyOwnerId);
        Id RTId = [SELECT Id FROM RecordType WHERE sObjectType ='Opportunity' LIMIT 1].Id;
        Boolean isRegional = false;
        acc= NEW account();
        acc= [select name,id,Sales_Region__c from Account where id =:oppty.Accountid];
        if(oppty.SMB_OPP_Must_Win_level__c == null)oppty.SMB_OPP_Must_Win_level__c='None';
        if(isRegional )
       oppty.SMB_Opp_Must_Win__c = 'Yes';
       else
       oppty.SMB_Opp_Must_Win__c = 'No';

        oppty.OwnerId = OpptyOwnerId;

       if(REC.name == System.Label.OAB_Opportunity_Record_Type){
       system.debug('========'+REC.name);
           oppty.StageName = '2 Qualification';
       }else{
           oppty.StageName = '1 Pre-qualification';
       }


         if(REC.name ==System.Label.OAB_Opportunity_Record_Type && acc.Sales_Region__c !='DEF'){
            system.debug('----------'+REC.name);
            ApexPages.addmessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'With a Simple DEF record type the account related to the opportunity must be a DEF account.'));
            return null;
        }


         if(REC.name ==System.Label.OAB_Opportunity_Record_Type && (oppty.Order_Type__c =='New Customer' || oppty.Order_Type__c =='New Business/GET')){
              oppty.Contract_Type__c= 'New';
        }else if(REC.name ==System.Label.OAB_Opportunity_Record_Type &&(oppty.Order_Type__c =='Renewal/KEEP' || oppty.Order_Type__c =='Organic/KEEP')){
                   oppty.Contract_Type__c= 'Existing';
        }

        insert oppty;

        //partner management evolution--START
        if(REC.name == System.Label.OAB_Opportunity_Record_Type){
            SMB_Partner__c insertNoPartner = new SMB_Partner__c(SMB_Opportunity__c=oppty.Id,
                                                                SMB_Name__c=Label.SMB_CL001_No_Partner_ID,
                                                               SMB_Amount__c=0,SMB_Percentage__c=0,
                                                               SMB_Primary__c=true);
            insert insertNoPartner;
        }
        //partner management evolution--END

        //assign a contact to a new opportunity
        if(conId!=null){
            OpportunityContactRole oppContact = new OpportunityContactRole(ContactId=conId,IsPrimary=true,
                                                                           OpportunityId=oppty.Id,Role=Label.Contact_Role);
            insert oppContact;
        }

          return oppty.Id;
    }
    catch(exception ex){
       if(!ex.getMessage().contains('FIELD_CUSTOM_VALIDATION_EXCEPTION'))
       Apexpages.addMessage(new Apexpages.Message(ApexPages.severity.ERROR, 'Exception Error: ' + ex));
       return null;
    }
  }

Error in $A.getCallback() ['state' is undefined]
Callback failed: apex://NewOpportunityController/ACTION$getNewOppId