I'am trying to store the query result in a String variable, but the result I'm getting is the string conversion of the query object.
tableDatabaseReference = FirebaseDatabase.getInstance().getReference("tables");
tableNameQuery = tableDatabaseReference.child("tableName").orderByChild(tableID).equalTo("123");
String tableName = tableNameQuery.toString();
Any suggestions?
EDIT:
Database structure:
Tables:
-------TableID:
--------------TableName:
--------------TableID:
To retrieve data from Firebase Realtime database , you have to add a valueEventListener to your database reference variable like this
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference dataRef = database.getReference("YOUR_DATABASE_REF");
dataRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// here you can get your data from this snapshot object
String data = dataSnapshot.getValue("CHILD_NAME_HERE").toString();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
To get data once you can use singleValueEventListener
dataRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// here you can get your data from this snapshot object
String data = dataSnapshot.getValue("CHILD_NAME_HERE").toString();
}
#Override
public void onCancelled(DatabaseError databaseError) {}
});
Firebase operation is asynchronous, so you have to wait to complete the operation to get result. To access data outside of onDataChange you can use LiveData and observe it outside. When you get data inside onDataChange then notify LiveData by posting value. Check below:
private MutableLiveData<String> tableName = new MutableLiveData<>();
DatabaseReference tableDatabaseReference = FirebaseDatabase.getInstance().getReference("tables");
tableDatabaseReference
.child(tableID)
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
String data = dataSnapshot.child("tableName").getValue(String.class);
//Now post that value to LiveData
tableName.postValue(data);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Observe data here
tableName.observe(this, name -> {
// use name here
});
So i have a viewholder which has the name of the user and Under it i wanna put the last message that this user received , i have a query that gives me the last node in the database there is my code :
Query lastQuery = allDb.child("ReceivedMessages").child(mCurrent_user_id).child(list_user_id).orderByKey().limitToLast(1);
lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String message = dataSnapshot.child("message").getValue().toString();
friendViewHolder.lastMessage.setText(message);
}
#Override
public void onCancelled(DatabaseError databaseError) {
//Handle possible errors.
}
});
and this is my database structure (also i'm sure that the referance is correct because whenever i assign all of the data to a textView it gives me the last node plus the message and date etc .. but i only want the message )
and this is my error
I hope this will do the job.
Query lastQuery = allDb.child("ReceivedMessages").child(mCurrent_user_id).child(list_user_id).orderByKey().limitToLast(1);
lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds: dataSnaphot.getChildren()) {
String message = ds.child("message").getValue().toString();
friendViewHolder.lastMessage.setText(message);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
//Handle possible errors.
}
});
I need a help in firebase database,
I am willing to create an app for a city like Kolkata, to find buses between different local stations, I want to save the data in database and user will input where to where they want to go, after clicking on search, list of available data will be shown,
But I need help in how should I save the data to fetch it easily with less complicated code.
You can save data easily with firebase
private void writeNewUser(String userId, String name, String email) {
User user = new User(name, email);
mDatabase.child("users").child(userId).setValue(user);
}
You can search from firebase like below
DatabaseReference mFirebaseDatabaseReference = FirebaseDatabase.getInstance().getReference();
Query query = mFirebaseDatabaseReference.child("users").orderByChild("name").equalTo("Fazal");
query.addValueEventListener(valueEventListener);
ValueEventListener valueEventListener = new ValueEventListener()
{
#Override
public void onDataChange(DataSnapshot dataSnapshot)
{
for (DataSnapshot postSnapshot : dataSnapshot.getChildren())
{
//TODO get the data here
User user = dataSnapshot.getValue(User.class);
}
}
#Override
public void onCancelled(DatabaseError databaseError)
{
}
};
EDIT:
Firebase dont have a great SQL like searches built in. You can either sort by values/key or you can equalto
https://firebase.google.com/docs/database/android/retrieve-data
for further details check fire-base documentation
https://firebase.google.com/docs/database/android/read-and-write
when you write data into firebase database used below code ..
make pojo class for insert data..
public class City {
public String name, code;
public City(String name, String code) {
this.name = name;
this.code = code;
}
}
then after when you insert data into firebase used below code..
private DatabaseReference mFirebaseDatabase;
private FirebaseDatabase mFirebaseInstance;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.register_layout);
mFirebaseDatabase = mFirebaseInstance.getReference("usersDb/UserTable");//define your database name and table name
}
// below method used insert data..
private void insertData(){
City city=new City("Ahmedabad","380016"); // you can add data also runtime.
mFirebaseDatabase.child(city.name).setValue(user);
}
// below method used to search data..
private void sqlQuery(){
DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
Query query = reference.child("usersDb").child("UserTable").orderByChild("name").equalTo("vikas#gmail.com");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for (DataSnapshot issue : dataSnapshot.getChildren()) {
Log.d("Value::",issue.getValue(User.class).email);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
I am querying on firebase to fetch data from last point which was previously fetched but it is always giving all the rows.
Code:
Query query = null;
query = mFirebaseDatabaseReference.orderByKey();
String lastKey = getLastKey();
if (!TextUtils.isEmpty(lastKey)) {
query.startAt(lastKey);
}
Please help
DatabaseReference databaseReference = Firebase.getInstance().getReference();
Query lastQuery = databaseReference.child("NODE_NAME").orderByKey().limitToLast(1);
lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
// you can get last node values..
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
//Handle possible errors.
}
});
// where NODE_NAME is the root of all these child keys.
I want to retrive the id that generated by firebase when I pushed value to it like next
I want to retrieve "-KGdKiPSODz7JXzlgl9J" this id for that email
I tried by getKey() but it return "users"
and when user get value it return the whole object from the id to profile picture and that won't make me get it as User object in my app
how solve this ?
Firebase users = myFirebaseRef.child("users");
users.orderByChild("email").equalTo("z#m.com").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
dataSnapshot.getKey();
Log.d("User",dataSnapshot.getRef().toString());
Log.d("User",dataSnapshot.getValue().toString());
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.d("User",firebaseError.getMessage() );
}
});
You can read the key from push() without pushing the values. Later you can create a child with that key and push the values for that key.
// read the index key
String mGroupId = mGroupRef.push().getKey();
....
....
// create a child with index value
mGroupRef.child(mGroupId).setValue(new ChatGroup());
mGroupId contains the key which is used to index the value you're about to save.
UPDATE 1:
it can obtain also by one line
String key = mDatabase.child("posts").push().getKey();
//**************************************************************//
after searching and trying a lot of things i came to 2 ways to do that
.
1. first one to get the key when i upload the post to the server via this function
public void uploadPostToFirebase(Post post) {
DatabaseReference mFirebase = mFirebaseObject
.getReference(Constants.ACTIVE_POSTS_KEY)
.child(post.type);
mFirebase.push().setValue(post);
Log.d("Post Key" , mFirebase.getKey());
}
i used it in my code to get the key after i have already pushed it to node for it in my database
public void getUserKey(String email) {
Query queryRef = databaseRef.child(Constants.USERS_KEY)
.orderByChild(Constants.USERS_EMAIL)
.equalTo(email);
queryRef.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//TODO auto generated
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
//TODO auto generated;
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
//TODO auto generated;
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
//TODO auto generated
}
#Override
public void onCancelled(DatabaseError databaseError) {
//TODO auto generated
}
});
}
When you fire a Firebase query there can potentially be multiple results. So when you ask for the value of a query, Firebase returns a list of items. Even if there is only one matching item, it will be a list of one item.
So you will have to handle this list in your code:
users.orderByChild("email").equalTo("z#m.com").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot child: dataSnapshot.getChildren()) {
Log.d("User key", child.getKey());
Log.d("User ref", child.getRef().toString());
Log.d("User val", child.getValue().toString());
}
}
In Java - Android Studio, you can get the unique pushed ID as the item is written to the db...
Per "Firebase's: Save Data on Android": You can use the reference to the new data returned by the push() method to get the value of the child's auto-generated key or set data for the child. Calling getKey() on a push() reference returns the value of the auto-generated key.
To get the reference at write time, instead of loading DATA with a single push()...
use push() to create a blank record in the database, return value is the record's reference.
use .getKey() to get the Key for that record.
use .setValue(DATA) to fill in the blank record
here's an example:
FirebaseDatabase fb_db_instance = FirebaseDatabase.getInstance();
DatabaseReference db_ref_Main = fb_db_instance.getReference("string_db_Branch_Name");
hashMap_record = new HashMap<String, String>(); //some random data
hashMap_record.put("key_Item1", "string_Item1");
hashMap_record.put("key_Item2", "string_Item2");
DatabaseReference blankRecordReference = db_ref_Main ;
DatabaseReference db_ref = blankRecordReference.push(); //creates blank record in db
String str_NEW_Records_Key = db_ref.getKey(); //the UniqueID/key you seek
db_ref.setValue( hashMap_record); //sets the record
I solved it to get id you need to use firebase url
String uid = firebaseRef.child("users").push().getKey();
Log.i("uid", uid);
this will give you the key KG.....
For those using TVAC Tutorials(https://www.youtube.com/watch?v=cSMMWOHkP68&list=PLGCjwl1RrtcTXrWuRTa59RyRmQ4OedWrt&index=16)
You can get Key using onClick method as follows:
viewHolder.mView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String key = getRef(position).getKey();
}
});
Just add new field to Users like userID, when you create new User add uid and than you can receive it by reading query
I'm doing it like this.
String userID;// in Users
Firebase users = myFirebaseRef.child("users");
users.orderByChild("email").equalTo("z#m.com").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Users user= dataSnapshot.getChildren().iterator().next().getValue(Users.class);
Log.d("User",user.getUserID());
}
#Override
public void onCancelled(FirebaseError firebaseError) {
Log.d("User",firebaseError.getMessage() );
}
});
I had faced this problem and I found the solution,
you can get it using this code:
dataSnapshot.getChildren().iterator().next().getKey()
// Unity, code in C#
{
reference = FirebaseDatabase.DefaultInstance.RootReference;
string s = reference.Push().Key;
reference.Child(s).Child(Username).SetValueAsync(Username);
Debug.Log(s);
}
Another Option to get the unique Post-id from firebase is by getting key (dataSnapshot.getKey()) in #Override method public void onChildAdded and maintaining it locally for example
private void attachDatabaseReadListener() {
if (mTaskEventListener == null) {
mTaskEventListener = new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Task friendlyMessage = dataSnapshot.getValue(Task.class);
friendlyMessage.setId(dataSnapshot.getKey());
System.out.println("friendlyMessage = " + friendlyMessage);
DummyContent.ITEMS.add(new DummyContent.DummyItem("" + DummyContent.ITEMS.size()+1,friendlyMessage.getStatus(),friendlyMessage.getSummary()));
}
public void onChildChanged(DataSnapshot dataSnapshot, String s) {}
public void onChildRemoved(DataSnapshot dataSnapshot) {}
public void onChildMoved(DataSnapshot dataSnapshot, String s) {}
public void onCancelled(DatabaseError databaseError) {}
};
mUserDatabaseReference.addChildEventListener(mTaskEventListener); // remove it
}
}
dataSnapshot.getKey will set the unique post id in Task Instance and can be used later to perform any update operation.
FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
DatabaseReference databaseReference1 = firebaseDatabase.getReference("users");
databaseReference1.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
String key = dataSnapshot1.getKey();
Log.d(TAG, "onCreate: key :" + key);
String email = dataSnapshot1.child("email").getValue(String.class);
String roomno =dataSnapshot1.child("address").getValue(String.class);
Log.d(TAG, "onDataChange: email: " + email);
Log.d(TAG, "onDataChange: address: " + address)
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Use this
mFirebaseDatabase=mFirebaseDatabase.getInstance().getReference("tablename");
Query query = mFirebaseDatabase.orderByChild("tablenme").getRef();
query.orderByChild("Id").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
String id =dataSnapshot1.child("Id").getKey();
String Name = dataSnapshot1.child("Name").getValue().toString();
String lastName= dataSnapshot1.child("lastname").getValue().toString();
flatDataGets.add(Name+"-"+lastname);
}
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(RagisterActivity.this, R.layout.support_simple_spinner_dropdown_item, DataGets);
arrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
mRegisterSpinner.setAdapter(arrayAdapter);
mRegisterSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
flatName =DataGets.get(position);
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Yes, you can retrieve the node or main child name by adding its name in that particular child as a key and value {main_child_name}.
Simply do similar:
HashMap<String, Object> hashLcl = new HashMap<>();
hashLcl.put("admin", firebaseUser.getUid());
hashLcl.put("name", textPrm);
DatabaseReference referenceLcl = FirebaseDatabase.getInstance().getReference();
String keyLcl = referenceLcl.child("GroupChats").push().getKey();
hashLcl.put("key", keyLcl);
Task task = referenceLcl.child("GroupChats").child(keyLcl).setValue(hashLcl);
task.addOnSuccessListener(aVoid -> {
//the data is added and now we are sure to do something related
});
This is the result:
String id = Objects.requireNonNull(task.getResult().getUser()).getUid();