APEX Aggregate Query to get Sum of Amount of all Opportunities of Account when record is updated Or Inserted Using Apex Trigger in Salesforce | Write Apex Trigger on Opportunities to Sum of Amount of all Opportunities of related Account Using Aggregate Query in Salesforce

   TRIGGER opportunityTrigger ON Opportunity (BEFORE INSERT, after INSERT, BEFORE UPDATE, after UPDATE) {

    IF(TRIGGER.isBefore){

        system.debug('I am inside before');

    }ELSE IF(TRIGGER.isAfter){

        system.debug('I am inside after');

        IF(TRIGGER.isUpdate){

            opportunityHandlerCtrl.updateOpportunity(TRIGGER.new);

        }ELSE IF(TRIGGER.isInsert){

           opportunityHandlerCtrl.updateOpportunity(TRIGGER.new); 

        }

    }

}

    public class opportunityHandlerCtrl {

    public static void updateOpportunity(List<Opportunity> oppList){

        Set<Id> setId = NEW Set<Id>(); 

        Map<Id, Decimal> accmap = NEW Map<Id, Decimal>();

        DECIMAL mydecval = 0;

        FOR(Opportunity oppObj : oppList){

            setId.add(oppObj.AccountId);

        }

        system.debug('setId ' + setId);

        List<AggregateResult> agrObj =[SELECT AccountId, SUM(Booking_Amount__c) totalAmount FROM Opportunity WHERE AccountId=:setId GROUP BY AccountId];

        FOR(Opportunity opt:oppList){

            FOR(AggregateResult agr:agrObj){

                mydecval = (DECIMAL)agr.get('totalAmount');

                accmap.put((Id)agr.get('AccountId') ,(DECIMAL)agr.get('totalAmount'));

                Account accItem = NEW Account(); 

                accItem.Id=(Id)agr.get('AccountId'); 

                accItem.Total_Booking_Revenue__c = mydecval;

                //system.debug('accmap44 ' + accItem);

                //system.debug('keySet111 ' + accmap.keySet());

                // system.debug('keyVal ' + accmap.values());

                // 

                Campaign cpm = NEW Campaign();

                cpm.Id = opt.CampaignId;

                cpm.ActualCost=mydecval;

                system.debug('cpm22 ' + cpm);

                UPDATE cpm;                

                UPDATE accItem;

            }

        }  

        system.debug('mydecval!! ' + mydecval);

    }

}