Vf page error when try to delete row on vf page

Question

I'm leaning a VF Page Creation. I'm try to create page from which i can save muliple account. in which i've to implement, add and remove row. i'm able to add row perfectly as required but unable to delete row.

My VF Page code:

<apex:page standardController="Account" sidebar="false" extensions="Accountextension">
    <apex:form >

     <apex:pageBlock title="Account Records Edit" id="Refresh" >
        <apex:pageBlockButtons location="both">
        <apex:commandButton value="Save" action="{!save}" />
        </apex:pageBlockButtons>

        <apex:pageBlockSection title="Adding Multiple Accounts" columns="1">
        <apex:pagemessages />

            <apex:pageBlockTable value="{!Acc}" var="a"  >
             <apex:variable value="{!0}" var="rowNumber" />
                <apex:column headerValue="Action">
                <apex:commandButton action="{!removeNewObject}" value=" X "  >
                <apex:param name="rowIndex" value="{!rowNumber}" />
                </apex:commandButton>
                <apex:variable var="rowNumber" value="{!rowNumber+1}"/>
                </apex:column>

                <apex:column headerValue="Account Name">
                <apex:inputField value="{!a.Name}"/>
                </apex:column>
                <apex:column headerValue="Account Type">
                 <apex:inputField value="{!a.Type}"/>
                </apex:column>
                <apex:column headerValue="Industry">
                <apex:inputField value="{!a.Industry}"/>
                </apex:column>


            </apex:pageBlockTable>
        <apex:commandLink value="Add Row" action="{!AddRow}" reRender="Refresh" />        

        </apex:pageBlockSection>

</apex:pageBlock>

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

Controller is :

public with sharing class Accountextension {
    public List<Account> Acc {get;set;}
    public Integer rowIndex { get; set; }

    public Accountextension(ApexPages.StandardController controller) {
        this.acc = new list<account>();
        this.acc.add(new Account());
    }

    public PageReference AddRow()
    {
        this.acc.add(new Account());
        return null;
    }  

    public PageReference removeNewObject(){
       Integer indexVal = Integer.valueof(system.currentpagereference().getparameters().get('rowIndex'));
       system.debug('%%%%%%%%'+rowIndex);
       system.debug('%%%%%%%%'+indexVal );

       if(acc[indexVal-1].Id != null)
       acc.remove(indexVal-1 ); 
       return null;
    }
}

Screen shot is

When I click on delete button ("X") it gives me error like

System.NullPointerException: Argument cannot be null. error at; Integer indexVal = Integer.valueof(system.currentpagereference().getparameters().get('rowIndex'));

I'm unable to understand what wrong here:

Answer 1

The core issue is that you need to use <apex:commandLink> here, not <apex:commandButton>. From the documentation for the <apex:param> tag:

The <apex:param> component can only be a child of the following components:

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

I also recommend using assignTo here, but that's not mandatory to get your page working, I believe. Here's a fully working demo you should only have to modify slightly to get your own page working.

Markup

<apex:page controller="Demo">
    <apex:form>
        <apex:variable value="{!0}" var="rowNumber" />
        <apex:repeat value="{!data}" var="i">
            <ul>
                <apex:commandLink action="{!removeNewObject}" value=" X ">
                    <apex:param name="rowIndex" assignTo="{!rowIndex}" value="{!rowNumber}" />
                </apex:commandLink>
                <apex:outputText value=" {!i}" />
                
                <apex:variable var="rowNumber" value="{!rowNumber+1}"/>
            </ul>
        </apex:repeat>
    </apex:form>
</apex:page>

Code

public with sharing class Demo
{
    public List<String> data { get; private set; }
    public Demo()
    {
        data = new List<String>();
        for (Integer i = 0; i < 10; i++)
            data.add(String.valueOf(i));
    }
    
    public Integer rowIndex { get; set; }
    public PageReference removeNewObject()
    {
        data.remove(rowIndex);
        return null;
    }
}