Develop Reference

how i get all data from firebase realtime database

I have a database with this schema:
I tested this code but I can't get any msg from the database. I would appreciate your help.
private void Add_Chat(final DataSnapshot dataSnapshot) {
root.child("ChatSpace").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
String nom=dataSnapshot.child("ChatSpace").child("msg").getValue(String.class);
System.out.println(nom); //prints "Do you have data? You'll love Firebase."
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

Assuming that ChatSpace is a direct chlid of your Firebase database root, to get all messages please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference chatSpaceRef = rootRef.child("ChatSpace");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String msg = ds.child("msg").getValue(String.class);
Log.d("TAG", msg);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
chatSpaceRef.addListenerForSingleValueEvent(eventListener);
Your output will be:
bbbName
bbbName
Name

Firebase Query get values

I have a list of Child-Data and wants to have a certain value.
My Firebase structure:
Now, I only have the Child "Text" and the currendUser "0zwtyRwgnogC8Qk91AtHj7amZb63"
So how can I get the values of "text and "user_id"?
My source code:
mDatabaseText = FirebaseDatabase.getInstance().getReference().child("Text");
query = mDatabaseText.startAt(mCurrentUser.getUid());
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for (DataSnapshot textSnapshot : dataSnapshot.getChildren()) {
/* String text = textSnapshot.getKey();
Toast.makeText(getActivity(), text, Toast.LENGTH_SHORT).show(); */
TextModel textModel = chatSnapshot.getValue(TextModel.class);
String t = textModel.getText();
Log.i("!!!!!!!text", t);
Toast.makeText(getActivity(), t, Toast.LENGTH_SHORT).show();
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
But this code doesn't work, why?
I used the query startAt.

Please use this code:
FirebaseDatabase rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference currentUserIdRef = rootRef.child("Text").child(currentUserId);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String userId = (String) ds.getKey();
DatabaseReference userIdRef = rootRef.child("Text").child(currentUserId).child(userId);
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String user_id = (String) dataSnapshot.child("user_id").getValue();
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
};
userIdRef.addListenerForSingleValueEvent(eventListener);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
};
currentUserIdRef.addListenerForSingleValueEvent(eventListener);
In which currentUserId is the variable that you say you already have it.
Hope it helps.

Firebase get all key

HI everyone I want to catch all the keys on my firebase database:
Users-
26dfg678-
Name: jack
Job: Farmer
43jkhjh4-
Name: bill
Job: ICT
I want to catch the id: 26dfg678 and 43jkhjh4 and put them in an array. This is my code:
final DatabaseReference database_nomi = firebaseDatabase.getReference().child("Users");
database_nomi.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
//here
**name[0] = dataSnapshot.getKey();
Provee.setText(name[0]);**
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
if i do this it takes only the last but i want all..

To do this you need to read through your Firebase snapshot using a ValueEventListener (and addListenerForSingleValueEvent).
databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
int i = 0;
for(DataSnapshot d : dataSnapshot.getChildren()) {
name[i] = d.getKey();
i++;
}
}
}//onDataChange
#Override
public void onCancelled(DatabaseError error) {
}//onCancelled
});
This code uses a foreach to read all dataSnapshot children, saving its key in an array at each iteration.

How to fetch the username list in listview in Android from Firebase database?

I have registered and saved users through my app and now I want to fetch the list of usernames as shown below from Firebase database. How do I do it in list view? my database is shown below:

ArrayList<MODELCLASSNAME> Users=new ArrayList<>();
DatabaseReference df=FirebaseDatabase.getInstance().getReference().child("users");
df.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapShot user : dataSnapshot.getchildren()){
Users.add(dataSnapshot.getValue(MODELCLASSNAME.class));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
//Now loop through your arraylist

get your database reference
firebaseDatabase = FirebaseDatabase.getInstance();
mPostDb = firebaseDatabase.getReference("User");
Now query your table
Query query = mPostDb.orderByKey();
query.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapShot user : dataSnapshot){
// Do what ever you whatever you want with this user object
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Try this method:
public void retrieveNames() {
Query myQuery = mDatabase.orderByChild("name").equalTo("INSERT-HERE-A-NAME-FOR-YOUR-SEARCH");
myQuery.addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
Iterator iterator = dataSnapshot.getChildren().iterator();
//FOR YOUR DATA STRUCTURE -
while (iterator.hasNext()) {
String image_uri = (String) ((DataSnapshot) iterator.next()).getValue();
String name = (String) ((DataSnapshot) iterator.next()).getValue();
String username = (String) ((DataSnapshot) iterator.next()).getValue();
YourUserObject User = new YourUserObject (image_uri, name, username);
YourArrayList.add(User);
}
YourAdapter.notifyDataSetChanged();
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

How can i get each child? Firebase getValue [android]

How could i get all the childs from my database?
This code get the first Element, how can i get Element_2,3 and successive? The best i accomplised is serialize the first country and print it.
My Database:
{
"Capitals" : {
"Country_1" : {
"Country" : "Macedonia",
"Capital" : "Skopje"
},
"Country_2" : {
"Country" : "Madagascar",
"Capital" : "Antananarivo"
},
"Country_3" : {
"Country" : "Malawi",
"Capital" : "Lilongwe"
}
}
My Code
#Override
public void onStart(){
super.onStart();
final FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference capitalsRef = database.getReference("Capitals");
compresoresRef.orderByChild("Ref").addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
countryModel cm = dataSnapshot.getValue(countryModel.class);
String country = cm.getCountry();
String capital= cm.getCapital();
textData1.setText(country);
textData2.setText(capital);
}
#Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
The dataSnapshot while executing looks like:
DataSnapshot { key =Country_1, value = {Country=Macedonia, Capital=Skopje} }

You should use an ArrayList for store all childs that you get from Firebase using addChildEventListener
ArrayList<countryModel> countryList = new ArrayList<countryModel)();
compresoresRef.orderByChild("Ref").addChildEventListener(new ChildEventListener() {
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
countryModel cm = dataSnapshot.getValue(countryModel.class);
countryList.add(cm);
...
}
}
Or if you use addValueEventListener for retrieve data, it will look like
compresoresRef.addValueEventListener(new ValueEventListener() {
public void onDataChange(DataSnapshot snapshot) {
countryList.clear();
for (DataSnapshot postSnapshot: snapshot.getChildren()) {
countryModel cm = postSnapshot.getValue(countryModel.class);
countryList.add(cm);
}
}
public void onCancelled(FirebaseError firebaseError) {
System.out.println("The read failed: " + firebaseError.getMessage());
}
});

Try this
#Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
for(DataSnapshot post:dataSnapshot.getChildren())
{
countryModel countryModel cm = post.getValue(countryModel.class);
}
}