How to COUNT OR SUM of Activity Histories ?

Hey Guys,

Here is the solution for Counting Activity Histories or Sum of Activity Histories ,

Lets take example of ACCOUNT's Activity Histories

Apex Controller

private List<String> contactIdList; // Variable declaration

contactIdList = new List<String>(); // put this line under the constructor

public List<Account> getCountofActivityHistories() {

            return [ select Name, Type, Owner.Name, Referring_Contact__c, CreatedDate, (select Id                                from ActivityHistories) from Account where Referring_Contact__c in :contactIdList                            order by Name limit 1000 ];

}

Visualforce Page

<apex:pageblocktable value="{!CountofActivityHistories}" var="item">

           <apex:column headerValue="Number of Activities">

                      <apex:outputText value="{!item.ActivityHistories.size}"/>

           </apex:column>

</apex:pageblocktable>