I tried each and every possibility to know where i'm going wrong but still no luck. My issue is my search (i.e. filter) is working on Subject,Status and Date field for Task object .

Now i want to search for one more column which is "OwnerId" . I know it can be done using if condition something like below  but what should be "IF condition " to get to the goal ?

if (logical condition  to filter by owner) {
    qStr + ' and OwnerId in :ownerIds';

I'm really paralyzed and need help.

public class PagingTasksController1{

    public List<Task> Tasks;

   
    public Task del;
    public Task taskDel;
    public Integer CountTotalRecords{get;set;}
    public String QueryString {get;set;}
    public Integer OffsetSize = 0;
    private Integer QueryLimit =3 ;
    public List<Task> lstTasks {get;set;}
    public String searchText {get;set;}
    public String rowIndex {get;set;}
//   public List<Task> attendeeList {get;set;}
    public Date mydate;
    public Integer totalCount {get;set;}
    public string sortField = 'Subject';  // default sort column
    private string sApplySOQL = '';
   public List<Task> delattendeeList {get;set;}

    public List<Task> delAttendees {get; set;}

    public PagingTasksController1(ApexPages.StandardController controller) {

     taskDel= (Task)controller.getRecord();
     Tasks = [Select id,Subject,Status,ActivityDate from Task where OwnerId =: taskDel.Id];
    // this.Tasks=Tasks[0];
     totalCount = Tasks.size();

     delattendeeList = new List<Task>();
     delattendees = new List<Task>();
}


// the current sort direction. defaults to ascending
    public String sortDir {
        get  { if (sortDir == null) {  sortDir = 'asc'; } return sortDir;  }
        set;
    }

    // the current field to sort by. defaults to role name
    public String getsortField() {
        return sortField;
    }

    // the current field to sort by.
    public void setsortField(string value) {
        sortField = value;
    }
            
    // toggles the sorting of query from asc<-->desc
    public void toggleSort() {
        // simply toggle the direction
        sortDir = sortDir.equals('asc') ? 'desc' : 'asc';
      
        integer iIndex = sApplySOQL.indexOf('Order By');
        if (iIndex > -1){
          sApplySOQL = sApplySOQL.substringBefore('Order By');
          sApplySOQL = sApplySOQL + ' Order By ' + sortField + ' ' + sortDir +  ' limit ' + QueryLimit + ' offset ' + OffsetSize;
        }
        tasks = Database.query(sApplySOQL );
    }
  
    public PagingTasksController1 (){
        //CountTotalRecords= [select count() from Task];
        //String qStr2= '7/23/2014';
          
    }

   public List<Task> getTasks(){
        if(tasks == null){
            tasks = new List<Task>();
        }
        return tasks;
    }

    public void findTasks(){
        String qStr2 = 'Select count() from Task where Subject like \'%'+searchText+'%\' OR Status like \'%'+searchText+'%\'';
        CountTotalRecords = Database.countQuery(qStr2);
        queryTasks();
    }

    public void  queryTasks(){
        
        String qStr2= searchText;
        String strnormal = '';
        try{
             mydate = date.parse(qStr2);
        }catch(Exception e)
        { }
           
        String strDate = '';
        if(mydate != null) {
         // strnormal = String.valueOf(mydate );
          String[] qstr3 = String.valueOf(mydate).split(' ',2); 
          strDate = ' ActivityDate =  '+ qstr3[0] + ' ';
        }else{
       
           strDate  =  'Subject like \'%'+searchText +'%\' OR Status like \'%' +searchText+ '%\' Order By '  + sortField;
        }
        String qStr = 'Select OwnerId,Subject,Status,ActivityDate from Task where '  + strDate   ;

         System.debug(qStr );
           
//        String qStr = 'Select OwnerId,Subject,Status,Priority from Task where Subject like \'%'+searchText+'%\' OR Status like \'%'+searchText+ '%\' Order By ' + sortField;

       
       
        sApplySOQL = qStr;
      
        tasks = Database.query(sApplySOQL );
        //tasks.sort();

    }

    public Boolean getDisablePrevious(){
        if(OffsetSize>0){
            return false;
        }
        else return true;
    }

    public Boolean getDisableNext() {
        if (OffsetSize + QueryLimit < countTotalRecords){
            return false;
        }
        else return true;
    }

    public PageReference Next() {
        OffsetSize += QueryLimit;
        queryTasks();
        return null;
    }

    public PageReference Previous() {
        OffsetSize -= QueryLimit;
        queryTasks();
        return null;
    }

      public PageReference save() {
        update tasks;
        return ApexPages.CurrentPage();
     }
    
    public void deleteRow(){

         rowIndex = String.valueOf(ApexPages.currentPage().getParameters().get('rowIndex'));
         System.debug('rowIndex ------------'+rowIndex );
         if(rowIndex!=null)
         {
         Task check=[Select id from Task where id=: rowIndex];
         System.debug('row to be deleted ' + check);
         delete check;
         Tasks=[Select Subject,Status,ActivityDate,OwnerId from Task ];
         update Tasks;
         }
     }
     
  }