jQuery Grid Plugin - jqGrid

Hello,

I have a problem. I have a grid loading data using JSON. I use the extended filter and I'd like to set some filter values and have the grid recovers the filtered data, but still allowing the user to change the filtered values. Using postData grid param I am able to set the filter, but it is not applied. How can I apply it automatically?

Here is my code:

jQuery("#list1").jqGrid( {

url:'json.php',

datatype: "json",

colNames:[ ... ], 

colModel:[ ... ],

mtype: "POST",

...

} );

jQuery("#list1").jqGrid('setGridParam', { postData: { filters:' { "groupOp":"AND","rules":[ { "field":"start","op":"bw","data":"2013-09" } ] } ' } , search:true } );

jQuery("#list1").trigger('reloadGrid');

Using this code, the grid still loads all data, but if I open the filter, I see the start "Begin with" 2013-09 value preset and it works if I press the "Find" button, but I want to receive the filtered data immediately, without opening the filter box and pressing Find.

What am I doing wrong?

Leandro