为datagrid、treegrid增加右键表头菜单，用于显示或隐藏列，注意：冻结列不在此菜单中

var createGridHeaderContextMenu = function(e, field) {
    e.preventDefault();
    var grid = $(this);/* grid本身 */
    var headerContextMenu = this.headerContextMenu;/* grid上的列头菜单对象 */
    if (!headerContextMenu) {
        var tmenu = $('<div style="100px;"></div>').appendTo('body');
        var fields = grid.datagrid('getColumnFields');
        console.log('id='+grid.attr('id'));
         storage=$.localStorage;if(!storage)storage=$.cookieStorage;
        var cols = storage.get(grid.attr('id')+'hiddenColumns');
        var init=true;
        if(cols){
            init=false;
        }
        for ( var i = 0; i < fields.length; i++) {
            var fildOption = grid.datagrid('getColumnOption', fields[i]);
            console.log(fields[i]+'='+fildOption.hidden);
            if (!fildOption.hidden||fildOption.hidden==false) {
                $('<div iconCls="icon-ok" field="' + fields[i] + '"/>').html(fildOption.title).appendTo(tmenu);
            } else {
                if(init==false){
                    for(var j=0;j<cols.length;j++){
                        if(cols[j].field==fields[i]&&cols[j].visible!=false){
                            //console.log(cols[j].field+'=='+cols[j].visible);
                            $('<div iconCls="icon-empty" field="' + fields[i] + '"/>').html(fildOption.title).appendTo(tmenu);
                        }
                    }
                }
            }
        }
        headerContextMenu = this.headerContextMenu = tmenu.menu({
            onClick : function(item) {
                var field = $(item.target).attr('field');
                if (item.iconCls == 'icon-ok') {
                    grid.datagrid('hideColumn', field);
                    $(this).menu('setIcon', {
                        target : item.target,
                        iconCls : 'icon-empty'
                    });
                } else if (item.iconCls == 'icon-empty') {
                    grid.datagrid('showColumn', field);
                    $(this).menu('setIcon', {
                        target : item.target,
                        iconCls : 'icon-ok'
                    });
                }else{
                    //恢复表头
                    
                }
            }
        });
    }
    headerContextMenu.menu('show', {
        left : e.pageX,
        top : e.pageY
    });
};

//$.fn.datagrid.defaults.onHeaderContextMenu = createGridHeaderContextMenu;     //屏蔽掉dagagrid表头右键隐藏列的功能
$.fn.treegrid.defaults.onHeaderContextMenu = createGridHeaderContextMenu;