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Thursday 2 August 2012

Pagination in Visualforce Page

Salesforce.com introduced the StandardSetController in Winter ’09 . The new pagination feature is pretty powerful and easy to use with standard as well as custom objects. Even though Jon Mountjoy has a good blog post here, there appears to be very little documentation or examples for pagination.
I threw together a small demo that allows you to page through the query results and select multiple items to process. Instead of simply returning the list of sObjects from the query locator’s current set, a collection of wrapper objects are returned enabling the user to check items for processing.
You can run this demo on my developer site.
paging1
PagingController.cls – Custom Controller
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public with sharing class PagingController {
 
 List<categoryWrapper> categories {get;set;}
 
 // instantiate the StandardSetController from a query locator
 public ApexPages.StandardSetController con {
  get {
   if(con == null) {
    con = new ApexPages.StandardSetController(Database.getQueryLocator([Select Id, Name FROM Cat3__c Order By Name limit 100]));
    // sets the number of records in each page set
    con.setPageSize(5);
   }
   return con;
  }
  set;
 }
 
 // returns a list of wrapper objects for the sObjects in the current page set
 public List<categoryWrapper> getCategories() {
  categories = new List<categoryWrapper>();
  for (Cat3__c category : (List<cat3__c>)con.getRecords())
   categories.add(new CategoryWrapper(category));
 
  return categories;
 }
 
 // displays the selected items
  public PageReference process() {
   for (CategoryWrapper cw : categories) {
    if (cw.checked)
     ApexPages.addMessage(new ApexPages.message(ApexPages.severity.INFO,cw.cat.name));
   }
   return null;
  }
 
 // indicates whether there are more records after the current page set.
 public Boolean hasNext {
  get {
   return con.getHasNext();
  }
  set;
 }
 
 // indicates whether there are more records before the current page set.
 public Boolean hasPrevious {
  get {
   return con.getHasPrevious();
  }
  set;
 }
 
 // returns the page number of the current page set
 public Integer pageNumber {
  get {
   return con.getPageNumber();
  }
  set;
 }
 
 // returns the first page of records
  public void first() {
   con.first();
  }
 
  // returns the last page of records
  public void last() {
   con.last();
  }
 
  // returns the previous page of records
  public void previous() {
   con.previous();
  }
 
  // returns the next page of records
  public void next() {
   con.next();
  }
 
  // returns the PageReference of the original page, if known, or the home page.
  public void cancel() {
   con.cancel();
  }
 
}
CategoryWrapper.cls – Wrapper class for the Categories
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public class CategoryWrapper {
 
    public Boolean checked{ get; set; }
    public Cat3__c cat { get; set;}
 
    public CategoryWrapper(){
        cat = new Cat3__c();
        checked = false;
    }
 
    public CategoryWrapper(Cat3__c c){
        cat = c;
        checked = false;
    }
 
    public static testMethod void testMe() {
 
     CategoryWrapper cw = new CategoryWrapper();
     System.assertEquals(cw.checked,false);
 
     CategoryWrapper cw2 = new CategoryWrapper(new Cat3__c(name='Test1'));
     System.assertEquals(cw2.cat.name,'Test1');
     System.assertEquals(cw2.checked,false);
 
    }
 
}
Category_Paging.page – Visualforce page
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<apex:page controller="PagingController">
  <apex:form >
    <apex:pageBlock title="Paging through Categories of Stuff">
 
      <apex:pageBlockButtons location="top">
        <apex:commandButton action="{!process}" value="Process Selected"/>
        <apex:commandButton action="{!cancel}" value="Cancel"/>
      </apex:pageBlockButtons>
      <apex:pageMessages />
 
      <apex:pageBlockSection title="Category Results -  Page #{!pageNumber}" columns="1">
        <apex:pageBlockTable value="{!categories}" var="c">
          <apex:column width="25px">
            <apex:inputCheckbox value="{!c.checked}"/>
          </apex:column>
          <apex:column value="{!c.cat.Name}" headerValue="Name"/>
        </apex:pageBlockTable>
      </apex:pageBlockSection>
    </apex:pageBlock>
 
    <apex:panelGrid columns="4">
    <apex:commandLink action="{!first}">First</apex:commandlink>
    <apex:commandLink action="{!previous}" rendered="{!hasPrevious}">Previous</apex:commandlink>
    <apex:commandLink action="{!next}" rendered="{!hasNext}">Next</apex:commandlink>
    <apex:commandLink action="{!last}">Last</apex:commandlink>
    </apex:panelGrid>
 
  </apex:form>
</apex:page>
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