;
citiesQuery.addValueEventListener(new ValueEventListener(){
@Override
public void onDataChange(DataSnapshot dataSnapshot){
列表与LT;字符串> cities = new ArrayList< String>(); (DataSnapshot postSnapshot:dataSnapshot.getChildren()){
cities.add(postSnapshot.getValue()。toString());
$ b $ p
$ b 从用户输入开始,到最后一个以用户输入,你得到所有匹配的项目
对于相对较短的项目列表Ryan的方法也将正常工作。但是上面的Firebase查询会过滤服务器端。
更新
p>
DatabaseReference databaseRef = FirebaseDatabase.getInstance()。getReference(39714936);
String input =G;
DatabaseReference cities = databaseRef.child(cities);
查询citiesQuery = cities.orderByKey()。startAt(input).endAt(input +\\\);
citiesQuery.addValueEventListener(new ValueEventListener(){
@Override
public void onDataChange(DataSnapshot dataSnapshot){
List< String> cities = new ArrayList< String>(); $ (DataSnapshot postSnapshot:dataSnapshot.getChildren()){
cities.add(postSnapshot.getValue()。toString());
}
System.out的b
$ b .println(cities);
}
@Override
public void onCancelled(DatabaseError databaseError){
});
并印上:
true
true
。
随意测试我的数据库: https:/ /stackoverflow.firebaseio.com/39714936
I'm new to Firebase and NoSQL. I have an Android Demo, with a City Autocomplete Text Field in which I want to populate the cities I have from my Firebase DB, while typing.
{ "cities":{
"Guayaquil":true,
"Gualaceo":true,
"Quito":true,
"Quevedo":true,
"Cuenca":true,
"Loja":true,
"Ibarra":true,
"Manta":true
}
}
This is what I have so far.
How can I retrieve from the DB cities that start with a letter (input from keyboard)? If I start typing "G", I want to receive "Guayaquil" and "Gualaceo".
If I use orderByValue
always returns an empty snapshot.
If I use orderByKey
return the whole list.
Query citiesQuery = databaseRef.child("cities").startAt(input).orderByValue();
citiesQuery.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> cities = new ArrayList<String>();
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
cities.add(postSnapshot.getValue().toString());
}
Note: If you can recommend a better data structure, you're welcome.
解决方案
@NicholasChen has identified the problem. But here's the way you'd implement using the 3.x SDK:
DatabaseReference cities = databaseRef.child("cities")
Query citiesQuery = cities.orderByKey().startAt(input).endAt(input+"\uf8ff");
citiesQuery.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> cities = new ArrayList<String>();
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
cities.add(postSnapshot.getValue().toString());
}
By starting at the user input and ending at the last string that starts with the user input, you get all matching items
For relatively short lists of items Ryan's approach will also work fine. But the above Firebase query will filter server-side.
Update
I just ran this code:
DatabaseReference databaseRef = FirebaseDatabase.getInstance().getReference("39714936");
String input = "G";
DatabaseReference cities = databaseRef.child("cities");
Query citiesQuery = cities.orderByKey().startAt(input).endAt(input + "\uf8ff");
citiesQuery.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> cities = new ArrayList<String>();
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
cities.add(postSnapshot.getValue().toString());
}
System.out.println(cities);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
And it printed:
true
true
So clearly matches two cities.
Feel free to test against my database: https://stackoverflow.firebaseio.com/39714936
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