Ext.require(['Ext.tree.*','Ext.data.*','Ext.window.MessageBox']);
Ext.define("Ext.ux.comboBoxtree",{
extend : "Ext.form.field.Picker",requires : ["Ext.tree.Panel"],initComponent : function() {
        var self = this;
Ext.apply(self,{
fieldLabel : self.fieldLabel,labelWidth : self.labelWidth
// pickerAlign : "tl"//悬浮到其上面
});
self.callParent();
    },createPicker : function() {
        var self = this;
        var store = Ext.create('Ext.data.TreeStore',{
proxy : {
type : 'ajax',?
url : self.storeUrl
},sorters : [{
property : 'leaf',direction : 'ASC'
},{
property : 'text',direction : 'ASC'
}]
                });
self.picker = new Ext.tree.Panel({
height : 300,autoScroll : true,floating : true,focusOnToFront : false,shadow : true,ownerCt : this.ownerCt,useArrows : true,store : store,rootVisible : false
});
self.picker.on({
beforehide : function(p) {
                        var records = self.picker.getView().getChecked(),names = [];
Ext.Array.each(records,function(rec) {
names.push(rec.get('text'));
                                });
// Ext.MessageBox.show({
                        // title : 'Selected Nodes',// msg : names.join('<br />'),// icon : Ext.MessageBox.INFO
                        // });
                        // alert(names.join(','));
self.setValue(names.join(','));
p.setVisible(true);// 隐藏树
}
                });
        return self.picker;
    },alignPicker : function() {
// override the original method because otherwise the height of
        // the treepanel would be always 0
var me = this,picker,isAbove,aboveSfx = '-above';
        if (this.isExpanded) {
picker = me.getPicker();
            if (me.matchFieldWidth) {
// Auto the height (it will be constrained by min and
                // max width) unless there are no records to display.
picker.setWidth(me.bodyEl.getWidth());
            }
            if (picker.isFloating()) {
picker.alignTo(me.inputEl,"",me.pickerOffset);// ""->tl
                // add the {openCls}-above class if the picker was
                // aligned above
                // the field due to hitting the bottom of the viewport
isAbove = picker.el.getY() < me.inputEl.getY();
me.bodyEl[isAbove ? 'addCls' : 'removeCls'](me.openCls
+ aboveSfx);
picker.el[isAbove ? 'addCls' : 'removeCls'](picker.baseCls
+ aboveSfx);
            }
        }
    }
});
Ext.onReady(function() {
            var com = Ext.create("Ext.ux.comboBoxtree",{
storeUrl : 'check-nodes.json',width : 270,fieldLabel : '行政区划',labelWidth : 60,renderTo : 'tree-div'
});
        });
http://www.sencha.com/forum/showthread.PHP?132328-CLOSED-ComboBox-using-Grid-instead-of-BoundList