查询返回的QuerySnapshot对象可以返回0个或多个DocumentSnapshot对象。在索引到
获取具有所需字段值的文档，但这不适用于
await FirebaseFirestore.instance
.collection('orders')
.where("id", isEqualTo: orderList[index].id)
.get()
.then((snapshot) {
snapshot.docs.first.reference.update({"status": 'Rejected'});
print("yes");
});
但这是
await FirebaseFirestore.instance
.collection('orders')
.where("id", isEqualTo: orderList[index].id)
.get()
.then((snapshot) {
//snapshot.docs.first.reference.update({"status": 'Rejected'});
print("yes");
});
错误
E/flutter(10845(：[错误：flutter/lib/ui/ui_start_state.cc(177(]未处理的异常：错误状态：无元素
docs数组之前，您应该检查是否有超过0的值。
await FirebaseFirestore.instance
.collection('orders')
.where("id", isEqualTo: orderList[index].id)
.get()
.then((snapshot) {
if (snapshot.docs.length > 0) {
snapshot.docs.first.reference.update({"status": 'Rejected'});
}
else {
// Figure out what you want to do if the list is empty.
// This means your query matched no documents.
}
});