Visualforce - Get Id of record from page to controller

Question

I am having trouble getting the Id from the selected record to pass to my controller. When I check my debug the value of "accId" reports back as NULL.

Here is my VF Page (code trimmed):

<apex:page controller="controller_AccountServicing" sidebar="false">

    <apex:form id="theForm">
        <div id="header">
            <b>Account Servicing Activities (This Week)</b>
        </div>

        <div id="section" >
            <apex:pageBlock id="thePage">

                <apex:pageBlockTable value="{!Activities}" var="acc" id="Detail" >


                    <apex:column style="align:center;text-align:center;">
                        <apex:facet name="header">Activity Name</apex:facet>
                        <apex:outputlink target="_blank" value="/{!acc.Id}">{!acc.Name}</apex:outputlink>
                    </apex:column>                 


                <apex:column >
                    <apex:commandButton value="Update" action="{!updateWindow}">
                        <apex:param name="activityId" assignTo="{!accid}" value="{!Acc.Id}"/>
                    </apex:commandButton>
                </apex:column>


                </apex:pageBlockTable>

            </apex:pageBlock>
        </div>

    </apex:form>
</apex:page>

Here is my controller (code trimmed):

public class controller_AccountServicing {
    //Create Variables
    list    <Account_Servicing_Activity__c> accActivities   = new list<Account_Servicing_Activity__c>();
    public  boolean renderPrompt    {get;set;}
    public  Id      accId           {get;set;}

    public controller_AccountServicing(){
        //Initilization items
        Id currentuser = system.UserInfo.getUserId();

    }

    public List<Account_Servicing_Activity__c> getActivities() {
            accActivities = [Select Id,Name,(OTHER FIELDS)
                            FROM Account_Servicing_Activity__c
                            ];

            return accActivities;   
    }

    public void updateWindow() {
        renderPrompt = TRUE;
        system.debug('Activity ID = ' + accId);
    }

    public void updateRecord() { 

        try {
            renderprompt = false;
        } catch(DmlException e) {
            ApexPages.addMessages(e);
            System.debug('The following exception has occurred: ' + e.getMessage());

        }

    }

}

Answer 1

apex:param is not supported on apex:commandButton. Either use a normal button and call an apex:actionFunction, or use an apex:commandLink.

The only elements that are supported with apex:param are as follows:

<apex:actionFunction>
<apex:actionSupport>
<apex:commandLink>
<apex:outputLink>
<apex:outputText>
<flow:interview>