如何从firebase中的值获取密钥

How do I get the key "-KLpcURDV68BcbAvlPFy" when I know the field "name" contains "efg" in the following structure in Firebase.

当我知道字段“name”在Firebase的以下结构中包含“efg”时，如何获得键“-KLpcURDV68BcbAvlPFy”。

clubs
    -KLpcURDV68BcbAvlPFy
        dept: "abc"
        desc: "xyz"
        name: "efg"
    -asdasdasddsad
        dept: "asda"
        desc: "asd"
        name: "adddd"

I tried this but it returned "clubs"

我试过了，但它返回了"俱乐部"

mDatabase.child("clubs").orderByChild("name").equalTo("efg").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String clubkey =dataSnapshot.getKey();

1 个解决方案

#1

That's because you're using a ValueEventListener. If the query matches multiple children, it returns a list of all those children. Even if there's only a single matches child, it's still a list of one. And since you're calling getKey() on that list, you get the key of the location where you ran the query.

这是因为您正在使用ValueEventListener。如果查询匹配多个子节点，则返回所有这些子节点的列表。即使只有一个匹配的孩子，它仍然是一个列表。由于您在该列表中调用getKey()，因此您将获得运行查询的位置的键。

To get the key of the matches children, loop over the children of the snapshot:

要获取匹配子节点的键，请对快照的子节点进行循环:

mDatabase.child("clubs")
         .orderByChild("name")
         .equalTo("efg")
         .addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
            String clubkey = childSnapshot.getKey();

But note that if you assume that the club name is unique, you might as well store the clubs under their name and access the correct one without a query:

但请注意，如果您假设俱乐部名称是唯一的，您不妨将俱乐部的名称存储在它们的名称下，并访问正确的名称，而无需查询:

mDatabase.child("clubs")
         .child("efg")
         .addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String clubkey = dataSnapshot.getKey(); // will be efg

#1