Get id from Current Page Url issue

Question

I have scenario redirecting from one visualforce page to another visualforce page using apex code and have also set some parameters for second visualforce page. I tried to retrive the id using apexpages.currentpage().getparameters().get(‘id’), but it is erroring out as attempt to de-reference a null object.

Here is my first visual force page :

<apex:page standardController="Account" extensions="Opportunity_list_by_RecordType_ext" >
<apex:form>
<apex:pageBlock title="Orders" id="orders">
<apex:outputLink value="/apex/OpportunityListView?{!account.id}" target="_top">Click Here</apex:outputLink>
     </apex:pageBlock>
     </apex:form>
</apex:page>

apex:outputLink value="/apex/OpportunityListView?{!account.id}" target="_top">Click Here</apex:outputLink

second visual force page:

<apex:page standardController="Account" extensions="OppListView">
<apex:form >
    <apex:pageBlock >
        <apex:pageBlockButtons >
            <apex:commandButton action="{!gotoAcct}" value="Back to Accounts"/>
        </apex:pageBlockButtons> 

    <apex:PageBlockSection title="Opportunity" id="scheduleProducts" columns="1">
    <apex:pageBlocktable value="{!scheduleArray}" var="e">
        <apex:column headerValue="Opportunity Name"><apex:outputLink value="{e.iOLI"/></apex:column>
        <apex:column headerValue="Stage"><apex:outputText value="{!e.iStageName}" /></apex:column>
        <apex:column headerValue="Amount"><apex:outputText value="{!e.iAmount}" /></apex:column>
        <apex:column headerValue="Close Date"><apex:outputText value="{!e.iCloseDate}" /></apex:column>
        <apex:column headerValue="Agency"><apex:outputText value="{!e.iAgency}" /></apex:column>
        <apex:column headerValue="Opportunity Record Type"><apex:outputText value="{!e.iRecordType}" /></apex:column>
    </apex:pageBlocktable>    
    </apex:PageBlockSection>

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

Controller for 2nd vf page:

public with sharing class OppListView {
private list<Opportunity> theMOpps = new list<Opportunity>();
public Account acct{get;set;}
   List<aOLIPlus> scheduleArray;
   public OppListView(ApexPages.StandardController ctrl){
       acct.Id = System.currentPageReference().getParameters().get('id');
        //this.acct = (Account)Ctrl.getRecord();
        theMOpps = [Select Name, StageName, Amount, CloseDate, Agency__c, RecordTypeId, RecordType.Name From Opportunity Where AccountId = :acct.Id Order By CloseDate DESC ];

        scheduleArray = new List<aOLIPLus>();
        for(Opportunity thisMaster : theOrders)        
            scheduleArray.add(new aOLIPlus(thisMaster, thisMaster.StageName, thisMaster.Amount, thisMaster.CloseDate, thisMaster.Agency__c,thisMaster.RecordTypeId,thisMaster.RecordType.Name));        
    }
   public List<aOLIPlus> getScheduleArray()
    {    
        return scheduleArray;
    }
    public PageReference gotoAcct()
    {            
        String str = 'google.com';//+ acct.id;
        PageReference newPage = new PageReference(str);
        newPage.setRedirect(false);
        return newPage;
    }


    //Wrapper class
     public class aOLIPlus
    {    
        public Opportunity iOLI {get; set;}
        public String iStageName {get; set;}
        public Decimal iAmount {get;set;}
        public Date iCloseDate{get;set;}
        public String iAgency {get; set;}
        public String iRecordType {get; set;}
        public Boolean selected {get; set;}       

        public aOLIPlus(Opportunity aa, String aStageName, Decimal aAmount, Date aCloseDate,String aAgency,String aRecordTypeId,String aRecordType)
        {
          iOLI = aa;
          iStageName = aStageName;
          iAmount = aAmount;
          iCloseDate = aCloseDate; 
          iAgency = aAgency;  
          iRecordType = aRecordType;
          selected = false;
        }    
    }
}

Answer 1

You button that creates the URL does NOT contain a parameter named id. In addition, in your controller you are not initializing the acct property.

In the VF page change:

<apex:outputLink value="/apex/OpportunityListView?{!account.id}" target="_top">

to

<apex:outputLink value="/apex/OpportunityListView?id={!account.id}" target="_top">

And in your controller add:

acct = New Account();