Develop Reference

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?

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)

Retrieving child's Information from Firebase back to android studio

I am new to Android Studio and Firebase itself. I understand that in order to get the child's data from its unique ID, I might need to use a Data Snapshot method. For example, I need to retrieve the name from Firebase database back to android studio application. How do I implement it in this case? Help would be much appreciated!
{
"0Zs7aiWplRRJ5IJ5pazuUOxIdqz2" : {
"name" : "yeo",
"pos" : "intern",
"team" : "nwrs"
},
"kaLCjJFoGETWCWH42kNkc90b5Ku1" : {
"2016" : {
"9" : {
"25" : {
".priority" : 0.0,
"AM" : "",
"OT" : "",
"OVN" : "",
"PM" : "",
"TPT" : ""
}
},
"10" : {
"1" : {
".priority" : 0.0,
"AM" : "zxc11",
"OT" : "12",
"OVN" : "33",
"PM" : "222",
"TPT" : "54"
},
"26" : {
"AM" : "aa",
"OVN" : "gg",
"PM" : "ccc",
"TPT" : ""
},
"29" : {
".priority" : 0.0,
"AM" : "dd",
"OVN" : "aa",
"PM" : "ss",
"TPT" : "2fd"
}
}
},
"name" : "Jing Yang",
"pos" : "Intern",
"team" : "NWRS"
}
}
Below is my current code
root.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Set<String> set = new HashSet<String>();
Iterator i = dataSnapshot.getChildren().iterator();
while (i.hasNext()){
set.add(((DataSnapshot)i.next()).getKey());
}
names.clear();
names.addAll(set);
arrayAdapter.notifyDataSetChanged();

I'll assume that root refers to the root of your database. In that case your onDataChange will get a snapshot of the entire data at that location. You can loop over them and get the properties of each child in turn with:
root.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Set<String> set = new HashSet<String>();
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
//set.add(childSnapshot.getKey());
set.add(childSnapshot.child("name").getValue(String.class));
}
names.clear();
names.addAll(set);
arrayAdapter.notifyDataSetChanged();
But I highly recommend that you create a Java class that represents the items in your list. In your case that can be as simple as:
public class Item {
public string name;
public string pos;
public string team;
}
Then you can read the items with:
root.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
Set<String> set = new HashSet<String>();
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
Item child = childSnapshot.getValue(Item.class);
set.add(item.name);
}
names.clear();
names.addAll(set);
arrayAdapter.notifyDataSetChanged();

How to use orderByKey() with DataSnapshot?

I am populating a list of programs in a RecyclerView. Now i need to sort the programs by the time added. So i thought of adding a timestamp object to each program.
But i read that the PushID is also generated from a timestamp. So i tried to use the orderByKey(). But i can't figure out that how can i use the query with the userSnapshot?
CODE
public void FetchData() {
ProgramItemList.clear();
mRef.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
for (DataSnapshot programSnapshot : userSnapshot.getChildren()) {
program = programSnapshot.getValue(Program.class);
ProgramItem item = new ProgramItem();
String pushID = programSnapshot.getKey();
item.setID(pushID);
item.setName(program.getTitle());
ProgramItemList.add(item);
}
}
}
mAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});
}
JSON
{
"subscriptions" : {
"han#gmail,com" : {
"-KDnhRwHjssOejrqyenP" : {
"category" : "Strength",
"goal" : "This workout can be done while on the phone!",
"length" : 1,
"title" : "Hello Workouts",
"weeks" : {
"week1" : [ "High Knees", "Jumping Jacks", "Burpees" ]
}
},
"-KDni3TN4NMyGXePyp92" : {
"category" : "Strength",
"goal" : "This workout can be done by a BABUJI",
"length" : 1,
"title" : "Indian Workouts",
"weeks" : {
"week1" : [ "Diamond Pushups", "Jackknives", "Pushups" ]
}
}
},
"obama#gmsil,com" : {
"-KDnfjROKeFAL9wccsxY" : {
"category" : "Mobility",
"goal" : "afternoon body weight workout",
"length" : 1,
"title" : "Afternoon HiiT",
"weeks" : {
"week1" : [ "High Knees", "Squats", "Lunges", "Diamond Push-ups", "Lying Triceps Lifts" ]
}
},
"-KDps90Dn6XtJc6Co00b" : {
"category" : "Strength",
"goal" : "goal",
"length" : 1,
"title" : "title",
"weeks" : {
"week1" : [ "Diamond Pushups", "Spiderman Push-up", "Wide Arm Push-ups", "Burpee Pushups" ]
}
}
}
}
}