I have the following data structure in my firebase. I am implementing a coupon based system where you enter a code in dialogue box and it is searched across the database. So I have been trying to figure out this but I haven't found the perfect query that can search the code, if found, then get all the other child values too.
Below is the code that i have been trying with:
private void couponsearch() {
final EditText taskEditText = new EditText(this);
AlertDialog.Builder dialog = new AlertDialog.Builder(this)
.setTitle("Akiba Yangu")
.setMessage("Enter Akiba Code Here.")
.setIcon(R.drawable.akyi)
.setView(taskEditText).setPositiveButton("SAVE",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
String stringe = taskEditText.getText().toString();
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("codes").orderByChild("code").equalTo(stringe).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Coupons coo = dataSnapshot.getValue(Coupons.class);
String name = dataSnapshot.getKey();
int codez = coo.getValuee();
code.setText(name);
if(dataSnapshot != null && dataSnapshot.getChildren().iterator().hasNext()){
for(DataSnapshot ds : dataSnapshot.getChildren()) {
codegotten();
}
}else {
nocode();
}
int val = coo.getValuee();
Akibasavings as = new Akibasavings();
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
System.out.println(val);
code.setText(name);
as.setName(name);
as.setAmount(val);
final Firebase ref = new Firebase("https://akiba-c9600.firebaseio.com/");
Firebase newRef = ref.child("Savings"+uid).push();
newRef.setValue(as);
sendNotification();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
public void onCancelled(FirebaseError firebaseError) {
//Username Does Not Exist
}
});
}
});
dialog.show();
}
I would like to search the code, check if it is really there or not: if it is there I need to get all the other values too, i.e there are three nodes in every child. code, brand, value. After I have checked that the code exists, I would like to also get the other values associated with it. Regards
To achieve this, i recomand you change the structure of your database a little bit by adding a new node named coupons. Your database should look like this:
Firebase-root
--- coupons
TTUUPP: true
KKLLOO: true
To check if a coupon exists in your database, just add a listener on the new created node and use exists() method. This is a coomon practice within Firebase named denormalization and is for simplify and reduce query and bandwith. This what you need.
What you need is Query.
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
Query mQuery = mDatabase.child("codes").orderByChild("code").equalTo(stringe);
mQuery.addListenerForSingleValueEvent(new ValueEventListener() {
// use single value event listener to detach listener immediately after query
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.getValue() != null) {
// code exists, cast your data to relevant object
// note that if multiple entries exists, you need to loop through them
} else {
// code does not exists
}
}
});
Read the official document here.
Note that you must remember to index your firebase properly! Query on firebase is not the same as local database query. If you do not index your firebase, the query will download everything under the codes section into user phone, before doing the search locally on user phone. This will consume high bandwidth and memory. Learn more about index here. Read about my personal issue with index previously here.
When you execute a query against the Firebase Database, there will potentially be multiple results. So the snapshot contains a list of those results. Even if there is only a single result, the snapshot will contain a list of one result.
Your onDataChange() needs to handle the fact that the snapshot contains a list of result by looping over DataSnapshot.getChildren():
mDatabase.child("codes").orderByChild("code").equalTo(stringe).addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
Coupons coo = childSnapshot.getValue(Coupons.class);
String name = childSnapshot.getKey();
int codez = coo.getValuee();
code.setText(name);
...
}
}
Related
I'm using firebase realtime db, and I'm storing a list of string in a particular storage reference. Currently, to add something to the list
I'm doing the following steps.
Read the database childreference
get the datasnapshot and check if it is null (which means first
time)
if it is null, directly set your local list
if dataSnapshot.getValue(); not null then (already data present in
the db, so need to append the new data to th e end of it.)
save the remote list from dataSnapshot.getValue(); to a local variable.
then add the new data to the end of it
now the local list contains all the items in remote as well as new
items. save this to the child reference
Below is the code I have written for that
DatabaseReference reference = root()
.child(userId)
.child(list_id);
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
reference.removeEventListener(this);
List<String> value = new ArrayList<>();
if (dataSnapshot.getValue() == null) {
value.add(message);
} else {
if (dataSnapshot.getValue() instanceof List && ((List) dataSnapshot.getValue()).size() > 0 && ((List) dataSnapshot.getValue()).get(0) instanceof String) {
value = (List<String>) dataSnapshot.getValue();
value.add(message);
}
}
reference.setValue(value, (databaseError, databaseReference) -> {
finish();
});
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
finish();
}
private void finish() {
Log.e(TAG,"save finished");
}
});
Thats a lot of steps to do a simple operation. Also , all the time I'm pulling the whole data from remote and appending the new data to it.
is there any easy way to do this? I tried with the 'push()' method as follows
DatabaseReference reference = root()
.child(userId)
.child(list_id).push();
But it adds a new key always to the value I add. Can anyone explain what is the proper way to do it with less code?
UPDATE:
My db structure is as shown below
The solution you gave it's very good but why to remove the listener inside the callback?
I'll write you the code to be more simpler. Please see it below:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference listIdRef = rootRef.child("list").child(list_id);
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> list = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String comment = ds.getValue(String.class);
list.add(comment);
}
//Do what you need to do with your list
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
Log.d(TAG, databaseError.getMessage());
}
};
listIdRef.addListenerForSingleValueEvent(valueEventListener);
Don't ignore errors.
The simplest way in which you can add a new child in your 08-10-18 node, without the need to get the enitire list, would be using only the following lines of code:
Map<String, Object> map = new HashMap<>();
map.put("5", "comment55");
rootRef.child("list").child(list_id).updateChildren(map);
But even a better solution would be to use instead of lists, maps and the children should be added using the push() method. So your database structure should look like this:
Fireabase-root
|
--- usr100
|
--- 08-10-18
|
--- randomId: "comment1"
|
--- randomId: "comment2"
|
--- randomId: "comment3"
|
--- randomId: "comment4"
And the code should look like this:
String key = rootRef.child("list").child(list_id).push().getKey();
Map<String, Object> map = new HashMap<>();
map.put(key, "comment5");
rootRef.child("list").child(list_id).updateChildren(map);
In this case you don't have to worry about the key, which is not a number anymore. Without the help of the push() method, you need to get the entire list, as explained in the first part of my answer, add the new element and the update the list in the database.
This is just an update to the existing accepted answer, which I tried and working. This is the same process with less lines of code, without using the ValueEventListener and making use of the updateChildren method as mentioned in the accepted answer.
DatabaseReference reference = deviceRootReference().child(userId).child(list_id).push();
Map<String, Object> map = new HashMap<>();
map.put(reference.getKey(), comment);
Tasks.await(reference.updateChildren(map));
NOTE: This code performs the db write synchronously (Tasks.await blocks the thread), so the above piece of code should run in a background thread only
I'm starting to code Android Apps with the database connection. As IDE I use Android Studio and Firebase for the database. This is my data structure in Firebase:
In my app, I need to fill a ListView with all the names. So I want the data from three children from the child "Rezepte" from the UUID child. I hope this is understandable.
I've done a lot of googling and I just can't figure out how this works. My current version of the java code is this:
final FirebaseUser user = firebaseAuth.getCurrentUser();
// trying to get the reference of the right path
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child(user.getUid()).child("Rezepte");
ref.addListenerForSingleValueEvent(
new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// calling a method which should read the data from the snapshot and put it into the ListView
fillList((Map<String, Object>) dataSnapshot.child(user.getUid()).child("Rezepte").getValue());
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(RezepteActivity.this, "Daten konnten nicht gelesen werden", Toast.LENGTH_SHORT).show();
}
});
}
private void fillList(Map<String, Object> entries) {
// loop to cycle through every child of "Rezepte" and get the names
for (Map.Entry<String, Object> entry : entries.entrySet()) {
Map singleEntry = (Map) entry.getValue();
// add the name to an ArrayList of all names
Rezepte.add((String) singleEntry.get("name"));
}
// put the data into the ListView
lvRezepte.addFooterView(lvRezepte, Rezepte, true);
}
The app always crashes and I don't really understand a lot in the debugger. But the error occurs already in the onDataChange void.
I would be really happy if someone could help me.
You're trying to traverse down the hierarchy in your result DataSnapshot when you've already done so in your query itself. So in your onDataChange() you need to just put:
fillList(datasnapshot.getValue()) //Map of results at /{uid}/Rezepte
Assuming that fillList method works properly, you should first fix the following line
fillList((Map<String, Object>) dataSnapshot.child(user.getUid()).child("Rezepte").getValue())
to
fillList((Map<String, Object>) dataSnapshot.getValue())
You already have a reference to Rezepte child of the current user when you declared it like this:
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child(user.getUid()).child("Rezepte")
Your snapshot has 1, 2, and 3 as children, so you shouldn't reinforce the path you declared in the reference.
To get all those names and add them to an ArrayList, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference rezepeteRef = rootRef.child(user.getUid()).child("Rezepte");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> list = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String name = ds.child("name").getValue(String.class);
list.add(name);
Log.d("TAG", name);
}
Log.d("TAG", list);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
rezepeteRef.addListenerForSingleValueEvent(eventListener);
my data look like this
and I simply want to add an object at index 3. How could I add it there. Is there any way to add an object without iteration or I have to iterate and getChildCount and then append new child("3") and it's data to it.
TransGenderBO transGenderBO = new TransGenderBO();
transGenderBO.setName("pushName");
transGenderBO.setAge(13);
mRef.child("").setValue(transGenderBO);
there is no method in mRef for getting child count and appending new item at 3 position..
Edit after using Frank code but still not working
Query last = mRef.orderByKey().limitToLast(1);
last.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int lastIndex = 0;
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
lastIndex = Integer.parseInt(childSnapshot.getKey());
}
TransGenderBO transGenderBO = new TransGenderBO();
transGenderBO.setName("pushName");
transGenderBO.setAge(13);
mRef.child(""+(lastIndex+1)).setValue(transGenderBO);
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(mContext,databaseError.getMessage(),Toast.LENGTH_LONG).show();
}
});
There is a good reason that the Firebase documentation and blog recommend against using arrays in the database: they don't work very well for multi-user applications where users can be offline.
To add the next element to your array here, you'll have to download at the very least the last element of the array to know the index of the next element:
Query last = root.orderByKey().limitToLast(1);
last.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int lastIndex;
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
lastIndex = Integer.parseInt(childSnapshot.getKey());
}
root.child(""+(lastIndex+1)).setValue(true);
}
But this has an inherent race-condition. When multiple users are adding elements to the array at the same time, they may end up writing to the same index.
To prevent this you can use a Firebase transaction. With this you get the current value from a location and in exchange return the new value you want at that location. This ensures that no data is overwritten between users, but means that you have to download the entire array.
And neither of these scenarios works when a user is not connected to the network.
Firebase instead recommends using so-called push IDs, which:
Generate a always-increasing key that is guaranteed to be unique.
Do not require reading any data - they are generated client-side and are statistically guaranteed to be unique.
Also work when a user is offline.
The only disadvantage is that they're not as easily readable as array indexes.
Get your data like this
private ArrayList<TransGenderBO> transGenderBO;
FirebaseDatabase.getInstance().getReference().child("Main")
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
transGenderBO = (ArrayList<TransGenderBO>) dataSnapshot.getValue();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
and set your value like this
TransGenderBO transGender = new TransGenderBO();
transGender.setName("pushName");
transGender.setAge(13);
FirebaseDatabase.getInstance().getReference().child("Main").child(String.valueOf(transGenderBO.size())).setValue(transGender);
or U can set this way too
TransGenderBO transGender = new TransGenderBO();
transGender.setName("pushName");
transGender.setAge(13);
TransGenderBO.add(transGender);
FirebaseDatabase.getInstance().getReference().child("Main")
.setValue(transGenderBO);
I've been trying to retrieve an element from my Firebase database using its key. I have a class User and users are present in database.
I want to retrieve an object user using its key with this method :
public User getConnectedUserByUId(final String uid){
DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = database.child("users");
final List<User> connectedUser= new ArrayList<User>();
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot item: dataSnapshot.getChildren()) {
if (item.getKey()==uid)
{
User user= dataSnapshot.getValue(User.class);
connectedUser.add(user);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
return connectedUser.get(0);
}
but it returns an empty list every time.
The issue is here:
if (item.getKey()==uid)
since you are comparing 2 String in java you have to use the method
string.equals(Object other) not the == operator.
Moreover, since you know the key of the data in Firebase you can use it to get the reference without cycling all children.
Something like:
DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = database.child("users").child(uid);
Here you try to check a very specific ID only on changed data. Instead, try using a Firebase Query with filterByKey and not using your own function to achieve that. Here's sample code that I would use to try to replace your function:
DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = database.child("users");
Query connectedUser = ref.equalTo(uid);
connectedUser.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
// TODO: handle the post here
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
// Getting Post failed, log a message
Log.w(TAG, "loadPost:onCancelled", databaseError.toException());
// ...
}
});
As specified in the Firebase documentation here: https://firebase.google.com/docs/database/android/lists-of-data#filtering_data
in the line : User user= dataSnapshot.getValue(User.class);
you have to put : User user= item.getValue(User.class);
and you have to check the id after you get the user:
if (user.getKey()==uid){
connectedUser.add(user);
}
There are 2 mistakes and a minor issue:
you are using == to compare two String objects. In java, this is true only if they are the same reference. Use equals instead.
addValueEventListener only adds a listener that gets invoked once after you add it and then every time something changes in the value you are listening to: this is an asynchronous behaviour. You are trying to get data synchronously instead. Please read something about this.
you are fetching useless data: you only need an object but you are fetching tons of them. Please consider to use the closest reference you can to the data you are fetching.
So, in conclusion, here's some code. I'd like to point out right now that forcing synchronous acquisition of naturaly asynchronous data is a bad practice. Nevertheless, here's a solution:
public User getConnectedUserByUId(final String uid){
DatabaseReference database = FirebaseDatabase.getInstance().getReference();
DatabaseReference ref = database.child("users").child(uid);
Semaphore sem = new Semaphore(0);
User[] array = new User[1];
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot item: dataSnapshot.getChildren()) {
if (item.getKey()==uid)
{
User user= dataSnapshot.getValue(User.class);
array[0] = user;
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
try
{
sem.tryAcquire(10, TimeUnit.SECONDS);
}
catch (Exception ignored)
{
}
return array[0];
}
EDIT: I've just seen that this post is very old. I'm not sure how I ended up here.
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.
#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
Try something like this to iterate over the children in the cities snapshot and add all the cities to an ArrayList of Strings.
ArrayList<String> cityList = new ArrayList<>();
databaseRef.child("cities").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
cityList.clear();
for (DataSnapshot data : dataSnapshot.getChildren()){
cityList.add(data.getKey);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.w(TAG, "getUser:onCancelled", databaseError.toException());
// ...
}
});
Editing this paragraph for clarity:
This will get all your cities read into the program memory so you can use that data to display the cities to the user. If the city list changes, so will the data the user sees. If the user is not online, this will not work. This puts a real time, online only listener on the database.
The logic in my mind is something like:
Set a value listener on the text box.
When user types, make a view display all the items in the array list
that start with the same substring that was typed.
Handle arrayIndex errors of course.
Hopefully this will get you on the right track. I am sure there are other ways you could implement it but this is what I would personally do. If you need help with the code to display the correct cities, start a chat with me and I can brainstorm with you.
Of course OrderByValue returns nothing because that's the booleans you have.
you can use the startAt and endAt methods to do so. (The below is Firebase 2.0's Code)
var ref = new Firebase("https://dinosaur-facts.firebaseio.com/dinosaurs");
ref.orderByKey().startAt("b").endAt("b\uf8ff").on("child_added", function(snapshot) {
console.log(snapshot.key());
});
You can explore more on the Firebase 3 documentation site here.
What Ryan did was right. However, you have to implement startAt on the dataSnapshot to make sure that your "live" search works.