jsontodart failed

[jaaksi]

这段json无法生成bean，是什么原因呢？ { "onsale": { "num": "11", "list": [ { "frame_tags": [ "" ], "layout": "0室0厅0卫", "frame_image": { "image_url": "http://img.ljcdn.com/110000-frame/04ffd65b-01bc-4b8b-ac62-f3ac99634bde5.jpg", "ext_name": "jpg" }, "frame_name": "linkframe", "building_area": "建面0", "price": "价格待定", "onsale_num": "未知", "sell_status": "在售", "update_state": "2020.5.1更新" } ] }, "saleout": { "num": "11", "list": [ { "frame_tags": [ "" ], "layout": "0室0厅0卫", "frame_image": { "image_url": "http://img.ljcdn.com/110000-frame/04ffd65b-01bc-4b8b-ac62-f3ac99634bde5.jpg", "ext_name": "jpg" }, "frame_name": "linkframe", "building_area": "建面0", "price": "价格待定", "onsale_num": "未知", "sell_status": "在售", "update_state": "2020.5.1更新" } ] }, "presale": { "num": "11", "list": [ { "frame_tags": [ "" ], "layout": "0室0厅0卫", "frame_image": { "image_url": "http://img.ljcdn.com/110000-frame/04ffd65b-01bc-4b8b-ac62-f3ac99634bde5.jpg", "ext_name": "jpg" }, "frame_name": "linkframe", "building_area": "建面0", "price": "价格待定", "onsale_num": "未知", "sell_status": "在售", "update_state": "2020.5.1更新" } ] } }