Pagination Next does not take to the next page

Question

My question is continuation of this question

The problem I'm facing now is that when I click on the Next button its not showing the next page of set and I have 25 rows, I have setPageSize = 5

In the visualforce page i have action in the form like this:

<apex:page action="{!init}" ....

Apex code:

public List<ProductWrapper> Products 
     {
      get 
      {
                List<Product2> products2 = new List<Product2>(); 
                list<ProductWrapper> pws = new list<ProductWrapper>();                 
               for(Product2 p : (List<Product2>)this.con.getRecords()) {  

                  if(p.Asset_Line_items__r.isEmpty()){
                     pws.add(New ProductWrapper(p,New Asset_Line_Item__c(Quantity__c = 0));
                     continue;
                 }
                   for(asset_line_items__c b : p.asset_line_items__r) { 
                        //ProductWrapper pw = new ProductWrapper(p,b);
                        ProductWrapper pw = new ProductWrapper((Product2)p,b);
                        pws.add(pw);
                 }
           }    
           Products2 = pws;
           return Products2;
        }
        set;
    } 

Here is wrapper class:

public class ProductWrapper {

    public Product2 product {get;set;}
    public asset_line_items__c ali {get;set;}    

    public ProductWrapper(Product2 p, asset_line_items__c ali) {
        product = p;
        this.ali = ali;
    }
}

Constructor:

 public void init() {
        this.con = new ApexPages.StandardSetController(SOQL);
        this.con.setpageNumber(1);
        this.con.setPageSize(5);
    }

Pagination code:

    public void first() {
         con.first();
     } 
     public void last() {
         con.last();
     } 
     public void previous() {
         con.previous();
     }

     public void next() {
         con.next();
     }


 public ApexPages.StandardSetController con;

    public Boolean hasNext {
        get {
            return con.getHasNext();
        }
        set;
    }

    public Boolean hasPrevious {
        get {
            return con.getHasPrevious();
        }
        set;
    }

    public Integer pageNumber {
        get {
            return con.getPageNumber();
        }
        set;
    }

    public Integer totalPageNumber {
        get {
            Decimal totalSize = this.con.getResultSize();
            Decimal pageSize = this.con.getPageSize();
            Decimal pages = totalSize/pageSize;
            return (Integer)pages.round(System.RoundingMode.CEILING);
        }
        set;
    }

Visualforce page:

<apex:pageBlock id="pb">
  <apex:pageBlockTable value="{!products}" var="a">                     
          <apex:column headerValue="quantity" >                            
                <apex:inputField value="{!a.ali.qty}" required="true" />                    
          </apex:column>
          <apex:column value="{!a.Name}" headerValue="Name"/> 
          <apex:column value="{!a.ProductName}" headerValue="P Name"/> 
  </apex:pageBlockTable>
</apex:pageBlock> 

<apex:outputPanel rendered="{!products.size>0}" styleClass="center">
                <apex:commandButton value="|< First" action="{!first}" rerender="properties" rendered="{!HasPrevious}" />
                <apex:commandButton value="Previous" action="{!previous}" rendered="{!HasPrevious}"  rerender="properties"/>
                Page {!pageNumber} of {!totalPageNumber}
                <apex:commandButton value="Next" action="{!next}" rendered="{!HasNext}"  rerender="properties"/>
                <apex:commandButton value="Last>|" action="{!last}" rendered="{!HasNext}" rerender="properties" />
            </apex:outputPanel>

Answer 1

I suspect the problem is with this line:

<apex:page action="{!init}" ....

And the corresponding controller method:

public void init() {
    this.con = new ApexPages.StandardSetController(SOQL);
    this.con.setpageNumber(1);
    this.con.setPageSize(5);
}

From the apex:page documentation for the action attribute:

This method will be called before the page is rendered and allows you to optionally redirect the user to another page. This action should not be used for initialization.

I suspect this is getting called when you are attempting to page the results, which is resetting the paging. Check you debug log to see what is going on when attempting to page the results.

There is a good example of implementing pagination using the StandardSetController in Visualforce page with pagination.

Answer 2

Yes, after ruining my Sunday finally found the cause of this insane silently failing pagination, I wish Salesforce could have more appropriate error message or some sort of indication to show in my case and yes I do have <apex:pageMessages ></apex:pageMessages> but still did not show any errors whatsoever.

The cause of my problem was:

When you fire an action via a button or command link it submits the entire form, meaning all the required fields in the form are checked.

Use use tags to split up the form into various groups of fields with their associated actions—when you fire an action in a region only the fields in that same region are sent.