Styjun

How to limit the number of children added to 02 from firebase or java code in android.
I am going to add the child from the android application I made.
And I want to give a message to user if the number of children of 02 alreary 100.
I have tried

DatabaseReference dref=FirebaseDatabase.getInstance().getReference()
 .child("Root").child("Time").child(2019).child(April).child(02);
dref.addValueEventListener(new ValueEventListener() 
 @Override
 public void onDataChange(@NonNull DataSnapshot dataSnapshot) 
 numberofpatients=dataSnapshot.getChildrenCount();
 
 @Override
 public void onCancelled(@NonNull DatabaseError databaseError) 

 
 );

does not work;

also tried

dref.addChildEventListener(new ChildEventListener() 
 @Override
 public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) 
 numberofpatients=dataSnapshot.getChildrenCount();
 

 @Override
 public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) 
 numberofpatients=dataSnapshot.getChildrenCount();
 

 @Override
 public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) 
 numberofpatients=dataSnapshot.getChildrenCount();
 

 @Override
 public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) 
 numberofpatients=dataSnapshot.getChildrenCount();
 

 @Override
 public void onCancelled(@NonNull DatabaseError databaseError) 

 
 );

after getting the count i use the following to check the condition

 if(numberofpatients>=3)
 android.support.v7.app.AlertDialog.Builder alert=
 new android.support.v7.app.AlertDialog.Builder(
 FillForm.this);
 alert.setTitle("List Full");
 alert.setMessage("Select another date!");
 alert.setCancelable(false);
 alert.setPositiveButton("Okay",
 new DialogInterface.OnClickListener() 
 @Override
 public void onClick(DialogInterface dialog, int which) 
 mDateSpinner.requestFocus();
 
 );

 alert.show();
 

Please Help, Only the idea needed.

You have to loop through and get the number of children in child("02")

example

FirebaseDatabase.getInstance().getReference().child("Time/2019/April/02").addValueEventListener(new ValueEventListener() 
 @Override
 public void onDataChange(DataSnapshot dataSnapshot) 
 if (dataSnapshot.getChildrenCount()==100)

 //code here
 

 

 @Override
 public void onCancelled(DatabaseError databaseError) 

 
 );