How do get selected item of list?

Question

I have a webpart .I add a listviewbyquary in createchildcontrols and a hyperlink in visualwebpart.

i use this

http://graegert.com/featured/using-the-editorpart-to-create-a-custom-listview-web-part

I want get selected item in ListView when hyperlink click. i use this code in webpart

<script >
function geturl()
{
var context = SP.ClientContext.get_current();
this.web = context.get_web();
var listId = SP.ListOperation.Selection.getSelectedList();
var list = this.web.get_lists().getById(listId);
var items = SP.ListOperation.Selection.getSelectedItems(context);  //Get selected   documents
var itemId = items[0];
var url="@Url"+itemId;
return url;
 </script>

and code in Hyperlink

<a href="javascript:geturl()" >click</a>

but don't work .

var context = SP.ClientContext.get_current(); is null

//Edit

This code return the value when i use in list page , but when i use on Webpart , don't work

Answer 1

First, you can't run postback (by defining postbackurl in your linkbutton). If postback occurs, javascript looses its context.

Just add simple html markup such as:

<a href="javascript:getSelectedItemUrl()">Click on me </a>

To get the id of the first selected list item:

SP.ListOperation.Selection.getSelectedItems()[0].id

If SP.ClientContext.get_current() is null, then you have to ensure SP.js is loaded first, like in this question:

ExecuteOrDelayUntilScriptLoaded(GetUrl, "SP.js")

So your code can be encapsulated in this ExecuteOrDelay..:

function getSelectedItemUrl() {
  ExecuteOrDelayUntilScriptLoaded(GetUrl, "SP.js");
}
function GetUrl() {
  return @url + SP.ListOperation.Selection.getSelectedItems()[0].id;
}

Answer 2

Have you checked that the script is for it is included? I had problem before that the correct script files not where included.