Value not being passed from VF page to Controller

Question

I am new to VisualForce and I am not able to get my head around how do I pass value from vf page to my apex class when I have list of data.

I am adding my code snippets below,

Vf Page:

<apex:page controller="PublicController">
<apex:form>
    <apex:pageBlock id="one">
        <apex:pageBlockTable value="{!credential}" var="account" id="theTable">
            <apex:column >
                <apex:facet name="header">Name</apex:facet>
                <apex:outputText value="{!account.Username__c}"/>
            </apex:column>
            <apex:column >
                <apex:facet name="header">Pass</apex:facet>
                <apex:outputText value="{!account.Password__c}"/>
            </apex:column>
            <apex:column > 
                <apex:commandButton value="click" action="{!LoginHere}"> 
                    <apex:param name="accid" value="{!account.Id}" assignTo="{!accid}" /> 
                </apex:commandButton>
            </apex:column>
        </apex:pageBlockTable>
    </apex:pageBlock>
</apex:form>

</apex:page>

Apex Class:

public class PublicController {

List<Credential__c> Credential=new List<Credential__c>();
public string accid {set;get;}

public void LoginHere(){
    System.debug(accid);
    for(Credential__c currCredential : credential){
        if(currCredential.Id == accid){
            System.debug('CurrCredential'+currCredential);
            break;
        }
    }
}

public List<Credential__c> getCredential(){

     Credential = [SELECT id,Username__c,Password__c FROM Credential__c];
     return Credential;
    
}

}

Do let me know if you need anything else from my side for better clarification.

Answer 1

Using some help I was able to find the issue,

I was missing rerender="resultPanel" in apex:commandButton.

Thank you for all the help!!!

Answer 2

List<Credential__c> Credential is not visible to the Visualforce runtime, because it is not written as public List<Credential__c> Credential { get; set; }. The variable must be public and have a getter and setter. In addition, if that were true, then getCredential() would no longer work. Also, you can use a Map to eliminate the for-if loop.

Your final code should look like:

public class PublicController {
  public List<Credential__c> credential { get; set; }
  public string accid {set;get;}

  // Public default constructor
  public void PublicController() {
    Credential = [SELECT id,Username__c,Password__c FROM Credential__c];
  }
  public void LoginHere(){
    System.debug(accid);
    Credential__c currentCredential = new Map<Id, Credential__c>(credential).get(accId);
  }
}

Alternatively, you could have written:

public void LoginHere() {
  Credential__c currentCredential = [
    SELECT Id, Username__c, Password__c
    FROM Credential__c
    WHERE Id = :accId
  ];
}

This would work with your current code:

public class PublicController {
  public string accid {set;get;}
  public void LoginHere() {
    Credential__c currentCredential = [
      SELECT Id, Username__c, Password__c
      FROM Credential__c
      WHERE Id = :accId
    ];
  }  
  public List<Credential__c> getCredential(){
       return [SELECT id,Username__c,Password__c FROM Credential__c];
  }
}

This second form has the advantage of not wasting Visualforce View State, which makes the page very marginally faster on large lists.