Develop Reference

Is there any query to retrieve the data present in list firebase android

I want to retrieve only that post where postCategory matches the user interest.
How can I achieve this type of query. Any Help??
Below is my json file of database..
"Posts" : {
"-MAKobGjdhMfJFwZ1kol" : {
"postCategory" : "Animals",
"postDesc" : "still",
"postImage" : "Image Link",
"postPersonName" : "Name",
"postPersonUid" : "CLQA22uZpLS1ErIrnoBTrC3xqBw2",
"postTitle" : "ek"
},
"Users" : {
"CLQA22uZpLS1ErIrnoBTrC3xqBw2" : {
"email" : "email",
"interest" : {
"-MA14zFcNfs1JAjux129" : {
"name" : "Developer"
},
"-MA14zFgzhL-MOBB7D6h" : {
"name" : "Shopping"
}
},
"name" : "Name",
"uid" : "CLQA22uZpLS1ErIrnoBTrC3xqBw2"
}

In firebase database you cannot have such queries.
You should use Firestore (https://firebase.google.com/docs/firestore) for such advanced queries.
firestore/query-data
firestore

To get all posts with postCategory equal to Animals, you'd do:
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Posts");
Query query = ref.orderBy("postCategory").equalTo("Animals");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
Log.i(TAG, postSnapshot.getKey()+": "+postSnapshot.child("postTitle").getValue(String.class));
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException();
}
}
If you want to retrieve posts for multiple categories, you'll have to perform a separate query for each of those and merge the results on your client.
I'd also recommend changing how you store the categories for a user. The idiomatic way is:
"Users" : {
"CLQA22uZpLS1ErIrnoBTrC3xqBw2" : {
"email" : "email",
"interest" : {
"Developer": true,
"Shopping": true
}
},
The reasons this is more common is that it automatically ensures that each value can occur only once in the interest object, since property names are by definition unique.

Firebase nested ValueEventListener

I have the following database structure -
{
"linking" : {
"shift-assign" : { // for every shift its assigned users
"key1" : {
"111" : true,
"222" : true
},
"key2" : {
"111" : true
}
},
"user-assign" : { // for every user its assigned shifts
"111" : {
"key1" : true,
"key2" : true
},
"222" : {
"key1" : true
}
}
},
"shifts" : {
"20191117" : {
"key1" : {
"endTime" : "00:00",
"numOfEmps" : 3,
"startTime" : "00:00",
"wage" : 0
},
"key2" : {
"endTime" : "00:00",
"numOfEmps" : 1,
"startTime" : "00:00",
"wage" : 0
}
}
},
"users" : {
"111" : {
"id" : "111",
"password" : "111"
},
"222" : {
"id" : "222",
"password" : "222"
},
"99999" : {
"id" : "99999",
"password" : "123",
}
}
}
Where a user can be assigned to several shifts and a shift can contain several users.
I'm currently trying to fetch all of the users assigned to a certain shift.
So the idea was attaching a ValueEventListener to linking/shift-assign/{shift-key}, run a loop and for every user-key , reference users/{user-key} and attach an inner ValueEventListener to read user object and add it to a userList.
Something like this :
mDatabase.child("linking/shift-assign").child(shiftKey)
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
if(dataSnapshot.exists()){
for(DataSnapshot ds : dataSnapshot.getChildren()){
mDatabase.child("users").child(ds.getKey())
.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot2) {
mUser user = dataSnapshot2.getValue(mUser.class);
userList.add(user);
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {}
});
}
adapter = new UsersAssignedAdapter(UsersAssignedActivity.this, userList);
lv.setAdapter(adapter);
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {}
});
I debugged it and noticed that the for loop is finished before the inner ValueEventListener is called, which is why I'm getting an empty list in my adapter. I'm guessing this is due to its asynchronous behavior.
So my question is - is there any way I can query all user ids and for each one perform another query?

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?:

Android - Save list of object property with specific key on Firebase

Let's consider a "UserBean" with a property "emails" that is an ArrayList<EmailBean>.
When saved in Firebase it's like :
"users" : {
"$userID" : {
"emails" : [
"0" : {
"type" : "first",
"address" : "google#google.com",
"private" : true
},
"1" : {
"type" : "second",
"address" : "firebase#firebase.com",
"private" : false"
}
],
"name" : "Mitch"
}
}
So is it possible to achieve something like this :
"users" : {
"$userID" : {
"emails" : [
"first" : {
"address" : "google#google.com",
"private" : true
},
"second" : {
"address" : "firebase#firebase.com",
"private" : false
}
],
"name" : "Mitch"
}
}
I would prefer to not having to save each address one at a time.
Maybe there's an annotation to tells Firebase to use this property as a key ?
Regards.

I recomend you using the code below:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference emailsRef = rootRef.child("users").child(userId).child("emails");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String type = ds.child("type").getValue(String.class);
ds.child("type").getRef().getParent().setValue(type);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
emailsRef.addListenerForSingleValueEvent(eventListener);
What have i tried with this code? So in order to achieve what you want, first of all we got the value of your type key. Then we get a step up in the tree and set the partent with the value of your type key for each particular node.
Having the value of type in stead of 0, 1 and so on, to get the work done, just remove the type key, from each node using removeValue() method directly on the reference.