Develop Reference

Getting Firebase child key under random key

I want to retrive division and rno from for all key in array and compare those values in array with two other strings. how to do that?

You can get all children. try below code:
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference reference = database.getReference();
reference.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot ds: dataSnapshot.getChildren()) {
String rno = ds.child("rno").getValue().toString();
String div = ds.child("division").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

I don't understand your question. But you can play on those who fulfill the requirements of the child and fulfill the conditions.
DatabaseReference roomRef = dbRef.child("Everybody Room List Messages");
ValueEventListener roomEventListener = new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot dsKey : dataSnapshot.getChildren()) {
for (DataSnapshot dsNick : dsKey.getChildren()) {
if (dsNick.child("nick").getValue().toString().equals(Nick)) {
dsNick.child("image").getRef().setValue("");
}
}
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
};
roomRef.addListenerForSingleValueEvent(roomEventListener);

UPDATE
So, if I understand, you need this code:
FirebaseDatabase database = FirebaseDatabase.getInstance();
database.getReference().addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot item: dataSnapshot.getChildren()) {
String snapDiv = item.child("division").getValue().toString();
String snapRno = item.child("rno").getValue().toString();
if(snapDiv.equals(divi) && snapRno.equals(roll)){
//Here you can do everythings you need because division and rno value are those you are searching.
}
}
}
});
I can't understand completly your question.
You need to retrieve for each child his division and rno value. After that you need to compare them with other variables. But in the session these variables are 2 and fixed or you need to compare with a list of pairs?
After that, assuming that the above question will be clarify, if strings are matches, you need to update the value of sub1, sub2,...,sub5 fields?
Please, give us more informations to understand your situation and give you more support.

how to retrieve data from fire base and assign to a string

I have a database in fire-base. In that I have a child node named "item1", under item1 i have two values
name
prize
I want to retrieve the name of item1 and I want to put it in a string called "foodname". How can I do that?
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference("menu");
Here I tried but did not find solution
String foodname; //this string should get the value as "diary milk"
mDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("menu").addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
//This will loop through all items. Add variables to arrays or lists as required
for (DatasnapShot snap : dataSnapshot.getChildren())
{
foodname = dataSnapshot.child("name").getValue().toString();
String prize = dataSnapshot.child("prize").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
You can fetch each child individually like such. Or you can make use of a Model or a Hashmap to fetch all of the data and then fetch the data you would like based on the Key

Using below code you can get food name
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference("menu");
mDatabase.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
String foodName = snapshot.child("name").getValue().toString();
String foodPrice = snapshot.child("prize").getValue().toString();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});

Retrieving any data from Firebase requires a correct database reference and eventListeners that can work for what you want.
To know more about eventListeners visit this link.
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("menu").child("item1");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(#NonNull DataSnapshot dataSnapshot) {
// this code will get only details from item1
foodname = dataSnapshot.child("name").getValue(String.class);
String price = dataSnapshot.child("prize").getValue(Integer.class);
//if you want details from multiple items, you have to loop over the child nodes like this
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
foodname = snapshot.child("name").getValue().toString();
String price = snapshot.child("prize").getValue().toString();
}
}
#Override
public void onCancelled(#NonNull DatabaseError databaseError) {
}
});

How to fetch data from firebase database

I want to show all data into Recycleview but only first image load other are not
shown recycleviewList anybody have idea about this.
mFirebaseInstance = FirebaseDatabase.getInstance();
// get reference to 'users' node
mFirebaseDatabase = mFirebaseInstance.getReference("items");
mFirebaseDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
String getImage= (String) dataSnapshot.getValue();
String ConvertImage;
ConvertImage = getImage.replaceAll("\\[",
"").replaceAll("\\]","");
String[] items = ConvertImage.split(",");
List<String> list = Arrays.asList(items);
Log.e("list",list.toString());
for (String item : list) {
arraylist.add(item);
setImg(arraylist);
}
}
#Override
public void onCancelled(DatabaseError error) {
// Failed to read value
}
});

To get all those link, please use the following code:
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference itemsRef = rootRef.child("items");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String link = ds.getValue(String.class);
Log.d("TAG", link);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
itemsRef.addListenerForSingleValueEvent(eventListener);
The output will contain, all those links from your item node.

If you are able to retrieve all the links and still only one image loads, then check the xml layout of single list item of RecyclerView and make sure the height is wrap_content and NOT match_parent like this
android:layout_height="wrap_content"

Firebase query in tree with depth and multiple children

I have a problem regarding querying the firebase database using a value and getting the specific node. My schema is shown here:
In my schema 'workLocations' belongs to an 'excavationWorks', and 'excavationWorks' belongs to an 'excavationLists'.
That means that the path to a specific workLocation is excavationLists/excavationWorks/workLocations/(specific workLocation)
The problem that I have is that I want to query the workLocations node by the location value (let's say London) and get the parent node (the red circled key which is the key of the specific workLocation).
I have search and read many posts but I haven't managed to make it work.
My code looks like this:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
Query query = reference.child("workLocations").orderByChild("location").equalTo("London");
query.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot workLoc : dataSnapshot.getChildren()) {
// do something with the individual "issues"
Log.d(TAG, workLoc.getKey());
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
Thank you

To achieve this, you need to query your database twice like this:
DatabaseReference reference = FirebaseDatabase.getInstance().getReference();
DatabaseReference workLocationsRef = reference
.child("excavationLists")
.child("excavationWorks")
.child("workLocations");
ValueEventListener valueEventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot dSnapshot : dataSnapshot.getChildren()) {
for(DataSnapshot ds : dSnapshot.getChildren()) {
String key = ds.getKey();
Query query = workLocationsRef.child(key).orderByChild("location").equalTo("London");
ValueEventListener eventListener = new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
String description = snapshot.child("description").getValue(String.class);
Log.d("description", description);
String partentKey = snapshot.getRef().getParent().getKey();
Log.d("partentKey", partentKey);
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
query.addListenerForSingleValueEvent(eventListener);
}
}
}
#Override
public void onCancelled(DatabaseError databaseError) {}
};
workLocationsRef.addListenerForSingleValueEvent(valueEventListener);

Displaying the database nodes from Firebase in a list in Android

A simple question:
Referring to my database image, I want to get the values of the children of node "user" in a list in an Activity, i.e. values "a" and "m" should be displayed in the list.
What should I use and how?

Please try this code:
DatabaseReference yourRef = FirebaseDatabase.getInstance().getReference().child("user");
yourRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
List<String> usersList = new ArrayList<>();
for (DataSnapshot ds : dataSnapshot.getChildren()) {
String userName = (String) ds.getKey();
usersList.add(userName);
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
});
This is the way in which you'll have in your list, a, m ans so on.
Hope it helps.

You can get the info from the docs here
List<User> allUsers = new ArrayList<>();
DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("user");
ref.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
allUsers.clear();
for (DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
allUsers.add(userSnapshot.getValue(User.class));
}
yourRecyclerViewAdapter.notifyDataSetChanged();
}
#Override
public void onCancelled(DatabaseError databaseError) {
// Getting Users failed, log a message
Log.w(TAG, "loadUser:onCancelled", databaseError.toException());
// ...
}
});