ext 4 check tree 联动选择

	var tree = Ext.create('Ext.tree.Panel', {
		.....
		viewConfig : {
			onCheckboxChange : function(e, t) {
				var item = e.getTarget(this.getItemSelector(), this
								.getTargetEl()), record;
				if (item) {
					record = this.getRecord(item);
					var check = !record.get('checked');
					record.set('checked', check);

					if (check) {
						record.bubble(function(parentNode) {
									parentNode.set('checked', true);
								});
						record.cascadeBy(function(node) {
									node.set('checked', true);
								});
					} else {
						record.cascadeBy(function(node) {
									node.set('checked', false);
								});
					}
				}
			}
		}
	});
});