Develop Reference

Firebase Iterate through entire database

I am trying to receive all the data from a firebase database, so I can place it into a Users class however I do not know how I will iterate through the entire database as I cannot interger (the i variable in the for loop) insert values into the child field.
My code is this:
myRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(dataSnapshot.exists())
{
String fullname = (String) dataSnapshot.child(userId).child("Fullname").getValue();
String country = (String) dataSnapshot.child(userId).child("Country").getValue();
String profilePicture = (String) dataSnapshot.child(userId).child("ProfilePicture").getValue();
String username = (String) dataSnapshot.child(userId).child("Username").getValue();
Toast.makeText(getApplicationContext(), "Testing with: " + fullname + country + profilePicture + username, Toast.LENGTH_SHORT).show();
Toast.makeText(getApplicationContext(), "Count : (4) - " + dataSnapshot.getChildrenCount(), Toast.LENGTH_SHORT).show();
showProfiles(dataSnapshot);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});
Database:
{
"Users" : {
"4PdlTlv3qjZ3BmDvrJyUut9Fnq43" : {
"Country" : "xx",
"Fullname" : "hh",
"ProfilePicture" : "htm/o/Images%2FSearchAdapter%2F4PdlTlv3qjZ3BmDvrJyUut9Fnq43%2FProfilePicture%2FProfilePic_2019.03.06.10.47.54.jpg.jpg?alt=media&token=b647708e-c6d5-4b45-bef0-3dc40301b73a",
"Username" : "hmack001"
},
"COg4r4io9hezhFpmK3adPucUXA93" : {
"Country" : "spain",
"Fullname" : "nat",
"ProfilePicture" : "hcom/o/Images%2FSearchAdapter%2FCOg4r4io9hezhFpmK3adPucUXA93%2FProfilePicture%2FProfilePic_2019.03.06.19.14.17.jpg.jpg?alt=media&token=8620b321-5cef-42f0-a828-dbb7c37c8e7d",
"Username" : "nat"
},
"Tw1xRxViygNsLqrQiaaMAvAduIu1" : {
"Country" : "uk",
"Fullname" : "harvey\n",
"ProfilePicture" : "t.com/o/Images%2FUsers%2FTw1xRxViygNsLqrQiaaMAvAduIu1%2FProfilePicture%2FProfilePic_2019.03.03.05.26.35.jpg.jpg?alt=media&token=c290e75a-5f92-4271-bcb5-c644fe1b14ef",
"Username" : "RGB"
},
"vOxr1RoDqgWogKK1lp9pfpTHc6w2" : {
"Country" : "scotland ",
"Fullname" : "greg greg",
"ProfilePicture" : "ot.com/o/Images%2FSearchAdapter%2FvOxr1RoDqgWogKK1lp9pfpTHc6w2%2FProfilePicture%2FProfilePic_2019.03.04.12.30.22.jpg.jpg?alt=media&token=27b024cf-0691-4121-8a27-26acf101ebc2",
"Username" : "greg"
},
"xecUOPeyMcQaQrgkU9ouDgK90Ai1" : {
"Country" : "ggh",
"Fullname" : "Da apply ",
"ProfilePicture" : "2FProfilePic_2019.03.03.04.58.50.jpg.jpg?alt=media&token=f35854c2-3ff9-4d18-9f7a-10c13f066c68",
"Username" : "gg"
}
}
}
I am aware that there is no attempt in this code to retrieve information from all the users fields, I do not understand the logic behind iterating through the database as I dont see where I can do Item 1, Item 2 etc.

Use this
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
System.out.println(childSnapshot.getKey());
System.out.println(childSnapshot.child("Country").getValue(String.class));
}

android: adding a new node

Need to add a new node "Completed" under the parent which will eventually contain all the information from the node "Requests" at end of the ride.
So basically, I need to create node "Completed" first but its not adding it.
database
{
"Requests" : {
"iowpxU6WKUWpzWJyfssSoOVCPFj2" : {
".priority" : "f8118c3k3v",
"destination" : "221 Prince William St",
"details" : {
"driver" : "nYIAHSYimJMHbMkXqDt9PQ0U3Nf2",
"location" : "27 Horsfield St",
"request status" : "accepted",
"ridePrice" : 3.75,
"rideStatus1" : "arrived at pickup",
"rideStatus2" : "rider in vehicle",
"rideStatus3" : "destination bound",
"rideStatus4" : "arrived at destination",
"rider" : "iowpxU6WKUWpzWJyfssSoOVCPFj2",
"riderPaid" : "true"
},
"Users" : {
"Drivers" : {
"nYIAHSYimJMHbMkXqDt9PQ0U3Nf2" : {
"driver" : "nYIAHSYimJMHbMkXqDt9PQ0U3Nf2",
"email" : "driver#me.com",
"name" : "driver",
"password" : "whatever",
"phone" : "5551212",
"rates" : "0"
}
},
"Riders" : {
"iowpxU6WKUWpzWJyfssSoOVCPFj2" : {
"avatarUrl" : "",
"email" : "rider#me.com",
"name" : "rider",
"password" : "whatever",
"phone" : "5551313",
"rates" : "0",
"riderId" : "iowpxU6WKUWpzWJyfssSoOVCPFj2"
}
}
}
}
addNewNode
private void addNewNode() { // TODO: ........ NOT ADDING NEW NODE :-| ..........
Toast.makeText(this, "addNewNode", Toast.LENGTH_LONG).show();
DatabaseReference newNode = FirebaseDatabase.getInstance().getReference("Completed");
newNode.child(riderId).push().addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Toast.makeText(DriverTripDetail.this, "addNewNode: onDataChange", Toast.LENGTH_LONG).show();
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
Any assistance on how I can fix this would be greatly appreciated.

The Firebase Database stores values at paths. If there is no value, the path does not exist.
Your code creates a reference to /Completed/$pushID. but doesn't set any value, so the path doesn't get created. Something like this will work, since it sets a value:
newNode.child(riderId).push().setValue(true)

android firebase saving data to realtime database

In android app I create a firebase user authenticated by phone number and it works fine then I update this user adding display name and this is fine too; in the end I want to save user's data into firebase database so I wrote this rule:
"users" : {
"$user_id" : { // firebase user uid
".read" : "$user_id === auth.uid",
".write" : "$user_id === auth.uid",
".validate": "newData.hasChildren(['enabled', 'group', 'name'])",
"enabled" : { ".validate" : "newData.isBoolean()" },
"group" : { ".validate" : "newData.isString()" },
"name" : { ".validate" : "newData.isString()" },
}
}
This doesn't work and I get returned "permission denied" altough the simulator shows everything is fine (in the simulation I use custom authentication and set firebase as provider with the user's uid).
the user's class is:
public class User {
public boolean enabled;
public String group;
public String name;
public User() { }
public User(boolean enabled, String group, String name) {
this.enabled = enabled;
this.group = group;
this.name = name;
}
}
and i try to save it by:
private void saveUserToDB() {
User newUser = new User(true, "operators", currentUser.getDisplayName());
mRootRef.child("users").child(currentUser.getUid()).setValue(newUser, new DatabaseReference.CompletionListener() {
#Override
public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
if (databaseError != null) {
Log.e("ERROR", "Data could not be saved " + databaseError.getMessage());
} else {
Log.e("SUCCESS", "Data saved successfully.");
}
}
});
}
Can anybody kindly help me to understand why this happens?
Thanks
UPDATE
below is a "schema" of how the database should be:
{
"messages" : {
"1763409620982" : { // timestamp
"position" : "position text",
"sender" : "sender name",
"text" : "message text"
},
"1763409734527" : { // timestamp
"position" : "position text",
"sender" : "sender name",
"text" : "message text"
}
...
},
"users" : {
"Yi79w0HgA4ZTNAMHadixzoO5PaR2" : { // firebase user uid
"enabled" : true,
"group" : "group 1",
"name" : "user display name"
},
"kX22c0GgL4ZTNAMHallfgoO4pBN1" : { // firebase user uid
"enabled" : true,
"group" : "group 2",
"name" : "user name"
}
...
}
}
and here's the full set of rules:
{
"rules": {
"messages" : {
".read" : "root.child('users').child(auth.uid).child('group').val() === 'group 1'",
".write" : "root.child('users').child(auth.uid).child('group').val() === 'group 2'",
"$tstamp" :{
".validate": "newData.hasChildren(['position', 'sender', 'text'])",
"position" : { ".validate" : "newData.isString()" },
"sender" : { ".validate" : "newData.isString()" },
"text" : { ".validate" : "newData.isString()" },
}
},
"users" : {
"$user_id" : {
".read" : "$user_id === auth.uid",
".write" : "$user_id === auth.uid",
".validate": "newData.hasChildren(['enabled', 'group', 'name'])",
"enabled" : { ".validate" : "newData.isBoolean()" },
"group" : { ".validate" : "newData.isString()" },
"name" : { ".validate" : "newData.isString()" },
}
}
}
}
as to the class user it's defined as above and only used into the method saveUserToDB

Try to add push() before setValue(): It will add new sub-node containing all the fields from object of User class:
mRootRef.child("users").child(currentUser.getUid()).push().setValue(and so on...

May be you need write permission?:

Get a specific child from Firebase

In my Firebase, I have a database for an app. Let's say this is my Firebase JSON:
{
"Users" :{
"User1":{
"City": "Genk"
}
,"User2":{
"City": "Hasselt"
}
,"User3":{
"City": "Genk"
}
,"User4":{
"City": "As"
}
,"User5":{
"City": "Genk"
}
}
}
Now what I want is an ArrayList with all the users with city Genk. How is this possible? I want to use this ArrayList to put the specific Users who live in the city Genk in a ListView.

I suggest you create another child from the root like "UsersCity", In that way you can just call this child and retrieve it to your listview. Here's what i did:
String key = mDatabase.child("post").push().getKey();
UserPost userPost = new UserPost(author,uid,setemoticon,postData,mDate,latlng);
Map<String, Object> postValues = userPost.toMap();
Map<String, Object> childUpdates = new HashMap<>();
childUpdates.put("/post/" + key,postValues);
childUpdates.put("/user-post/" + uid + "/" + key, postValues);
mDatabase.updateChildren(childUpdates);
Here's the Json output for that :
{
"post" : {
"-KcGVPpS9CTWPNax61wf" : {
"authorName" : "Test 1",
"dateCreated" : {
"dateCreated" : 1486352395887
},
"postDescription" : "sample post",
"postEmotion" : 2130837658,
"userId" : "KTcgauWoJugXUsq6TAgrdqUvVYm1"
}
},
"user-post" : {
"KTcgauWoJugXUsq6TAgrdqUvVYm1" : {
"-KcGVPpS9CTWPNax61wf" : {
"authorName" : "Test 1",
"dateCreated" : {
"dateCreated" : 1486352395887
},
"postDescription" : "sample post",
"postEmotion" : 2130837658,
"userId" : "KTcgauWoJugXUsq6TAgrdqUvVYm1"
}
}
},
//This child node is for users where you'll want to get the $uid to use for creation of other child nodes.
"users" : {
"KTcgauWoJugXUsq6TAgrdqUvVYm1" : {
"fullname" : "Test 1"
}
}
}
I am just a newbie programmer and I know my answer is not the best but I hope it could help you out with your problem. :)

just fetch specific node data and its working perfect for me
mFirebaseInstance.getReference("yourNodeName").getRef().addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
Log.e(TAG, "======="+postSnapshot.child("email").getValue());
Log.e(TAG, "======="+postSnapshot.child("name").getValue());
}
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
Log.e(TAG, "Failed to read app title value.", error.toException());
}
});

How to prevent duplicated uname of Users Firebase [duplicate]

This question already has answers here:
How do you prevent duplicate user properties in Firebase?
(2 answers)
Closed 6 years ago.
I am adding username for my Chat App to Firebase Database successfully.
I implemented in activity:
FirebaseDatabase firedb = FirebaseDatabase.getInstance();
in createUser Method.
private void createUser(String uname){
Map<String,Object> newUser = new HashMap<String, Object>();
newUser.put("uname",uname);
DatabaseReference dbref = firedb.getReference();
dbref.child("Users").push().setValue(newUser);
}
When user click a button this method works. This method work correctly but I want to make uname primary key. I do not want to add a username if it is alerady exists.
Database Structure:
Rules:
{
"rules": {
".read": true,
".write": true
}
}
Finally, how to prevent duplicated uname ?

You have to add a top level /uname/ Node. Your data will be like this for example :
{
"Users" : {
"user1" : {
"uname" : "value1",
},
"user2" : {
"uname" : "value2",
},
"user3" : {
"uname" : "value3",
},
},
"uname" : {
"value1": "user1",
"value2": "user2",
"value3": "user3",
}
}
Now you have to Enforce New Data Structure:
{
"rules": {
"users": {
"uname": {
".validate": "!root.child('uname').child(newData.val()).exists()"
},
}
}
}