How to get child value of child from firebase in android?

To access the value in your database, you create a DatabaseReference

location for that. Here are three links to places in your database:

DatabaseReference zonesRef = FirebaseDatabase.getInstance().getReference("ZONES");
DatabaseReference zone1Ref = zonesRef.child("ZONE_1");
DatabaseReference zone1NameRef = zone1Ref.child("ZNAME");

      

        
        
        
      

    

In this snippet:

• zonesRef
  
  points to /ZONES
  
  
• zone1Ref
  
  points to /ZONES/ZONE_1
  
  
• zone1NameRef
  
  points to /ZONES/ZONE_1/ZNAME
  
  

See the Firebase documentation on getting a database link for more information.

You can attach a listener to each of the links to get the value at that location. For example, to get the value /ZONES/ZONE_1/ZNAME

:

zone1NameRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Log.i(TAG, dataSnapshot.getValue(String.class));
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "onCancelled", databaseError.toException());
    }
});

      

        
        
        
      

    

For more information on this type of read operation, see the Firebase Reading Values ​​documentation .

If you listen instead /ZONES/ZONE_1

, you get the DataSnapshot

entire node with all its properties. Then you use DataSnapshot.child()

to get from it ZNAME

:

zone1Ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Log.i(TAG, dataSnapshot.child("ZNAME").getValue(String.class));
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "onCancelled", databaseError.toException());
    }
});

      

        
        
        
      

    

One level higher, you can listen /ZONES

, which will give you a snapshot of all areas. Since this handles multiple children, you need to iterate over them with DataSnapshot.getChildren()

:

zonesRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot zoneSnapshot: dataSnapshot.getChildren()) {
            Log.i(TAG, zoneSnapshot.child("ZNAME").getValue(String.class));
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "onCancelled", databaseError.toException());
    }
});

      

        
        
        
      

    

For more information, see the Firebase documentation on listening for lists of data .

Finally, you can query to find a specific zone, for example to find a zone with "ZCODE": "ECOR"

:

Query zonesQuery = zonesRef.orderByChild("ZCODE").equalTo("ECOR");
zonesQuery.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot zoneSnapshot: dataSnapshot.getChildren()) {
            Log.i(TAG, zoneSnapshot.child("ZNAME").getValue(String.class));
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Log.w(TAG, "onCancelled", databaseError.toException());
    }
});

      

        
        
        
      

    

To learn more about this, read the Firebase documentation on Sorting and Filtering Data .