How to download specific item from FireBase, but not all list with items?

Question

我想从FireBase数据库中获取特定项目，例如，我的FireBase中有带有汽车的数组，每辆汽车都有一个唯一的ID，我只想下载按ID搜索的特定汽车，并且想将其解析为Car java对象，而无需下载所有不必要的汽车清单。

Answer 1

An alternative to your self-answer is to store the cars under their id:

cars
  car_1
    make: ...
    model: ...
  car_2
    make: ...
    model: ...

Then you can access the cars without needing a query, which means things will scale a lot better:

var id = 2;
ref.child('cars').child('car_'+id)...

Note that it is considered a bad practice to store array indices as keys in Firebase, which is why I prefixed the ids with car_ .

Answer 2

First go to specific list of objects which you want to search using .child("cars") , after that get specific element you want to campare in this example is carId, .orderByChild("carId") and finaly check if its value equals to your .equalTo("2") . The final result is fireBaseRef.child("cars").orderByChild("carId").equalTo("2"); this will return all cars with id of 2. If you know better way please write here :)