Hi 
I am newbie to lightning components
scenario: The user will enter contact name in an inputtext box and it will show contact firstname and phone, when he clicks on the contact name
               hyperlink then it will show further details of contact object.

I have  created a static resource for bootstrap and I am calling the classes in the component & application

// 1. apex class to handle server side methods
public class ContactController 
{
   @AuraEnabled  
   public static List<Contact> FindAll()
   {
      return [select ID,Name,Phone from Contact LIMIT 20];
   }
   
    //Get contacts based on Contact Name
    @AuraEnabled
    public static List<Contact> FindByName(String searchKey)
   {
      String name='%'+searchKey+'%';
       return [select ID,Name,Phone from Contact where Name LIKE:name LIMIT 100];
   }
    
    //Get contacts based on Contact ID, single record
    @AuraEnabled
    public static Contact FindByID(String conID)
   {
      return [select ID,Name,Account.Name,Phone from Contact where ID=:conID LIMIT 100];
   }
}

// 2 lightning component : contactList_comp
<aura:component controller="ContactController">
    
	<aura:attribute name="contacts1"
                    type="Contact[]"/>  
    
    <aura:handler name="init"
                  value="{!this}"
                  action="{!c.doInit}"/>
    
    <ul class="list-group">
        <aura:iteration items="{!v.contacts1}"
                        var="con">
        <li class="list-group-item">
            <a href="{!'#con/'+con.ID}">
                <p>{!con.Name}</p>
                <p>{!con.Phone}</p>
            </a>
        </li>
   </aura:iteration>
    </ul>
</aura:component>

// 3 . client side controller for the component
({
	doInit : function(cmp,event)
    {
	    var action=cmp.get("c.FindAll");
        action.setCallback(this,function(a)
        {
            cmp.set("v.contacts1",a.getReturnValue());
                        
        });
        $A.enqueueAction(action);
  	},
    
    searchkeychange : function(cmp,event,helper)
    {
	    var search_key=event.getParam("c.searchkey1");
        var action=cmp.get("c.FindByName");
        
        action.setParams({"search_key":searchkey1});
        
        action.setCallback(this,function(a)
        {
           cmp.set("v.contacts1",a.getReturnValue());
        });
        $A.enqueueAction(action);
	}
})

//4 search bar component
<aura:component >
	<input type="text"
           class="form-control"
           onkeyup="{!c.searchkeychange}"
           placeholder="Enter contact Name">
    </input>
</aura:component>

//5 client side controller for search bar component
({
	searchkeychange:function(component,event,helper) 
    {
		var myEvent=$A.get("e.c:searchkeychange"); 
        
        myEvent.setParams({"searchkey1":event.target.value});
       
        myEvent.fire(); 
  	}
})

// 6 event for search bar component
<aura:event type="APPLICATION" 
            description="Event template">

    <aura:attribute name="searchkey1"
                    type="String">
    </aura:attribute>
</aura:event>

//7. Now I create a an application
<aura:application >
    <link href='/resource/bootstrap/' 
          rel="stylesheet">
    </link>
    
    <div class="navbar navbar-default navbar-static-top"
         role="navigation">
    
           <div class="container">
               <div class="navbar-header">
                <a href="#" class="navbar-brand">Lightning Contacts</a>
                   
               </div>
           
           </div>
    </div>
    <div class="container">
        <div class="row">
               <div class="col-sm-12">
                   <c:searchbar_comp />
                   <c:ContactList_comp />
              </div>
                   
        </div>
    </div>    
</aura:application>

when I preview the app, it displays list of contacts but when I enetr any contact name in textbox , it throws an error as follows:

" This page has an error. You might just need to refresh it. Action failed: c$searchbar_comp$controller$searchkeychange [myEvent is undefined] Failing descriptor: {c$searchbar_comp$controller$searchkeychange} "

Please help me out in understad this.

Thanks
pooja