This question has been answered by Bruno17. See the first response.
{
"formtabs":"[]",
"contextmenus":"",
"actionbuttons":"",
"columnbuttons":"",
"filters":"[]",
"extended":{
"migx_add":"Voeg een evenement toe",
"formcaption":"",
"update_win_title":"",
"win_id":"jevenementen",
"maxRecords":"",
"addNewItemAt":"bottom",
"multiple_formtabs":"",
"extrahandlers":"",
"packageName":"jevenementen",
"classname":"JEvenementen",
"task":"",
"getlistsort":"",
"getlistsortdir":"",
"use_custom_prefix":"0",
"prefix":"",
"grid":"",
"gridload_mode":1,
"check_resid":1,
"check_resid_TV":"",
"join_alias":"",
"has_jointable":"yes",
"getlistwhere":"",
"joins":"",
"cmpmaincaption":"Evenementen",
"cmptabcaption":"Evenementen",
"cmptabdescription":"Evenementen toevoegen of bewerken",
"cmptabcontroller":"",
"winbuttons":"",
"onsubmitsuccess":"",
"submitparams":""
},
"columns":[
{
"MIGX_id":2,
"header":"Nummer",
"dataIndex":"ev_id",
"width":100,
"sortable":"false",
"show_in_grid":1,
"renderer":"",
"clickaction":"",
"selectorconfig":"",
"renderchunktpl":"",
"renderoptions":"[]"
},
{
"MIGX_id":3,
"header":"Jaar",
"dataIndex":"ev_jaar",
"width":100,
"sortable":true,
"show_in_grid":1,
"renderer":"",
"clickaction":"",
"selectorconfig":"",
"renderchunktpl":"",
"renderoptions":"[]"
},
{
"MIGX_id":1,
"header":"Naam",
"dataIndex":"ev_naam",
"width":200,
"sortable":true,
"show_in_grid":1,
"renderer":"",
"clickaction":"",
"selectorconfig":"",
"renderchunktpl":"",
"renderoptions":"[]"
}
]
}