Firebase Database Read Data

Firebase Database Read Data - android

I am trying to read some values from Firebase Real time database.
My structure looks like this:
and my code to retrieve the value("Wine and Dine"):
databaseReference.child("test").child("event_name").child("drinks")
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Object dataSnapshotObject = dataSnapshot.getValue(String.class);
if(dataSnapshotObject != null){
Toast.makeText(content, "Event Name: " + dataSnapshotObject.toString(), Toast.LENGTH_LONG).show();
}else
Toast.makeText(context,"null",Toast.LENGTH_SHORT).show();
}
#Override
public void onCancelled(DatabaseError databaseError) {
});
However, I only get a null response as the value. What could I be doing wrong?

You may remove .child("drinks") from the chain (and put it in later, as in code below)and if you want to make the dataSnapshotObject to String anyway, then you should retrieve it in a String.
Something like this:
String value = dataSnapshot.child("drinks").getValue(String.class);
Also check if your databaseReference looks something like this or not.
DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();

You can use addListenerForSingleValueEvent to get the value
Code sample:
FirebaseDatabase.getInstance().getReference().child("test").child("event_name").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
HashMap hashUser = (HashMap) dataSnapshot.getValue();
if (hashUser != null) {
String Drinks = hashUser.get("drinks").toString();
//Toast.makeText(this, Drinks , Toast.LENGTH_SHORT).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Related

Android + Firebase: retrieve multiple values and get the sum

Hello, I am new to Android development, so I'm hoping for your understanding. I would like to ask how I can retrieve all data under 'values' and get the sum. As you can see, the 'keys' are random-generated keys, which were sent from an Arduino device to Firebase, but the values being sent to Firebase are correct. I want to get the sum and display it on an Android app in a single TextView. I am using Android Studio as IDE for my Android app.
I've tried other snippets from Stack Overflow as well, but it's too confusing for my level of knowledge in Android and I can't make it work. Thank you.

Try like this, may be this will help to achieve your task.
DatabaseReference ref=FirebaseDatabase.getInstance().getReference();
ref.child("data/values").addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int toalSum=0;
if (dataSnapshot.getValue() != null) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
//depending upon what datatype youre using caste to it.
totalSum = totalSum+(int)snapshot.getValue();
}
Log.d("LOG","Toatal sum-"+totalSum)
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Try this dataSnapshot.getChildrenCount() will return size
DatabaseReference dbref=FirebaseDatabase.getInstance().getReference();
dbref.child("url/values")
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int size = dataSnapshot.getChildrenCount(); //Here u can see the count
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

To count those values, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference valuesRef = rootRef.child("data").child("values");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int sum = o;
for(DataSnapshot ds : dataSnapshot.getChildren()) {
int value = ds.getValue(Integer.class);
sum = sum + value;
}
Log.d("TAG", sum);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
valuesRef.addListenerForSingleValueEvent(eventListener);
Your outout will be:
1780

try this basic split string.
database.geteDatabase().getReference().child("data").child("values")
.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
//dataSnapshot.getValue().toString() = {a=1,b=2,c=3}
String[] value = dataSnapshot.getValue().toString().split("[{,}]");
String[] getA= value[1].split("="); //value[1]='a=1'
String[] getB= value[2].split("="); //value[2]='b=2'
String[] getC= value[3].split("="); //value[3]='c=3'
//what you want to do here.
}
#Override
public void onCancelled(DatabaseError databaseError) { }
});
this can use for other get basic multi value from firebase database.

Firebase query not giving result set

I have Firebase data organized in the below format. When I'm trying to fetch data using the below code, it just never enters onDataChange, even though I have data in Firebase at that path.
Please ignore the list part, in the log I am able to see right path of Firebase, i.e.:
conversation/8masp4NLZrYL4HpziIU7uUZjRd73/8masp4NLZrYL4HpziIU7uUZjRd73
DatabaseReference databaseReferenceAdapter = FirebaseDatabase.getInstance().getReference();
DatabaseReference conversation2Ref = databaseReferenceAdapter.child("conversation").child(currentUser).child(userListRef.get(position));
Log.d(TAG,"Data binding++++" + conversation2Ref.getRef().toString());
conversation2Ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Log.d(TAG,"Data changed");
Conversation conversationInfo = dataSnapshot.getValue(Conversation.class);
mConversationList.add(position,conversationInfo);
Log.d(TAG,"Data changed");
}
#Override
public void onCancelled(DatabaseError databaseError) {
Log.d(TAG,"Data error");
}
});

To get those values, instead of using Conversation.cass, you can use the String.class like this:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference yourRef = rootRef.child("conversation").child("8masp4NLZrYL4HpziIU7uUZjRd73").child("8masp4NLZrYL4HpziIU7uUZjRd73");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String message = dataSnapshot.child("message").getValue(String.class);
long notificationCount = dataSnapshot.child("notificationCount").getValue(Long.class);
long profileId = dataSnapshot.child("profileId").getValue(String.class);
String profileName = dataSnapshot.child("profileName").getValue(String.class);
long time = dataSnapshot.child("time").getValue(String.class);
String type = dataSnapshot.child("type").getValue(String.class);
Log.d("TAG", message);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
yourRef.addListenerForSingleValueEvent(eventListener);

child(userListRef.get(position));
The above is wrong, according to the database you have random push() key under the userid. So, you have to retrieve the push key and add it to the child.
to retrieve the key:
String key=conversation2Ref.push().getKey()
then in query do:
child(key)

Android - getValue from Firebase returns null

I am setting the value of a child in Firebase, but when I get the value from Firebase the value is null. I don't understand why.
database.child("User").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int depositInteger = 0;
try {
depositInteger = Integer.parseInt(depositText.getText().toString().trim());
} catch (NumberFormatException e) {
if (depositText.equals("")) {
Toast.makeText(getActivity(), "Failed", Toast.LENGTH_SHORT).show();
}
}
database.child(user.getDisplayName()).child("deposit").setValue(depositInteger);
Long previousDeposit = dataSnapshot.child("User").child(user.getDisplayName()).child("deposit").getValue(Long.class);
System.out.println("VAAAALUE: " + previousDeposit);
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

To set a value, you can use setValue() method directly on the reference like this:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference userRef = rootRef.child("Users").child(user.getDisplayName());
userRef.child("deposit").setValue(9); //Sets the value to 9
To get the value, please use the following code:
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int deposit = dataSnapshot.child("deposit").getValue(Integer.class);
Log.d("TAG", deposit);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
userRef.addListenerForSingleValueEvent(eventListener);
Please see the correct DatabaseReference which contains Users and not only User as shown in your screen-shot.

According your database structure the child you should reference is Users and in your code you are calling User. Fix that mistake...
//Replace child tag by Users to fix the error
database.child("Users").addValueEventListener(new ValueEventListener() { ...

Get last node in Firebase database Android

I want to get item in the last node added in firebase database from my Android. You can see on the image below i'm not sure how to get the specific node, because unique key is created by Firebase. How to reference to auto-created node and child inside? Thanks a lot
The last node

Try this:
DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
Query lastQuery = databaseReference.child("mp").orderByKey().limitToLast(1);
lastQuery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String message = dataSnapshot.child("message").getValue().toString();
}
#Override
public void onCancelled(DatabaseError databaseError) {
// Handle possible errors.
}
});
Hope this helps!

This might work:
DatabaseReference db = FirebaseDatabase.getInstance().getReference().child("mp");
Query query = db.orderByKey().limitToLast(1);
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot child: dataSnapshot.getChildren()) {
Log.d("User key", child.getKey());
Log.d("User val", child.child("message").getValue().toString());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
// TODO: Handle errors.
}
});

I prefer to write and retrieve data through objects.
MyObject is POJO.
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
MyObject myObject = data.getValue(MyObject.class);
Log.i(TAG, data.getKey() + " = " + myObject.toString());
}
}

console.log('last messages', messages[messages.length-1]);

Get the pushed ID for specific value in firebase android

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();

Develop Reference

The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.

Firebase Database Read Data - android

Related

Android + Firebase: retrieve multiple values and get the sum

Firebase query not giving result set

Android - getValue from Firebase returns null

Get last node in Firebase database Android

Get the pushed ID for specific value in firebase android

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