To show chatter followers or to record follower details on a Visualforce page, use the <chatter:followers> tag. The <chatter:followers> tag has a few attributes:

The following code snippet shows the use of these attributes:

<apex:page showChat="true">
 <Chatter:followers entityId="00590000001qt4z"/>
</apex:page>

In the preceding code, entityId is the user ID (Rakesh Gupta); so, in output, it will show the followers of the mentioned user; it can be done in the same way for records.

To make the preceding functionality dynamic, Apex code is required. Following is the sample code to control the dynamic behavior of the page.

First create a list of users in your organization. The following code shows whether users from your organization are active or inactive. According to your need, you can modify query in code. To create a dropdown of the available users in an organization, the Visualforce code to be used is as follows:

<apex:outputLabel value="Select user"></apex:outputLabel>
<apex:selectList id="user" value="{!uName}" size="1" title="User">
<apex:selectOptions value="{!users}" ></apex:selectOptions>
<apex:actionSupport event="onchange" action="{!followchange}" rerender="feed" status="loadStatus"/>
</apex:selectList>

The following is the controller code:

public List
<selectOption>
  getUsers()
  {
  List
  <selectOption>
    options = new List
    <selectOption>
      ();
      options.add(new selectOption('', 'Current User'));
      for (User users : [SELECT Id, Name FROM User ]) 
      {
      options.add(new selectOption(users.Id, users.Name));
      }
      return options;
      }

From this page, select any username from the dropdown; it will show the followers accordingly. To control the dropdown and show the followers dynamically, refer to the following Visualforce and controller code snippet:

<apex:outputPanel id="feed">
  <chatter:followers entityId="{!uid}"/>
</apex:outputPanel>
<apex:actionStatus id="loadStatus" startText="Loading..." /> 

public PageReference followchange() 
          {
            uid=uName;
            
          }

On the Visualforce page, use the output panel to display the outcome. In the entityId attribute of the chatter:followers tag, use {!uid} to get the list of followers from the controller.

<apex:outputPanel id="resultPanel">
  <b>Followers ({!followers.size})</b>
  <apex:dataList value="{!followers}" var="f">
    <apex:outputText value="{!f.Subscriber.Name}">
    </apex:outputText>
  </apex:dataList>
</apex:outputPanel>

followers=  [select id, subscriberid, subscriber.name
      from EntitySubscription
      where parentid =:uid];