How to check existing data when using push ID using Firebase? - firebase

Question

I have some problem on checking existing data on firebase. i want to check data date , timeIn and timeOut before inserting data into firebase. The code that i make doesnt work because its check data by push id.
private void addCourtBooking(){
CourtBookingDatabase.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
if ((dataSnapshot.child(dateinput.getText().toString()).exists() && dataSnapshot.child(timeStartSpinner.getSelectedItem().toString()).exists()) && dataSnapshot.child(timeEndSpinner.getSelectedItem().toString()).exists()) {
Toast.makeText(getApplicationContext(), "Exist", Toast.LENGTH_LONG).show();
}else {
UCourtType = txtCourtType.getText().toString();
UPurpose = sp.getSelectedItem().toString();
UDate = dateinput.getText().toString();
UTimeStart = timeStartSpinner.getSelectedItem().toString();
UTimeEnd = timeEndSpinner.getSelectedItem().toString();
Map CourtBookinginformation = new HashMap();
CourtBookinginformation.put("courtType",UCourtType);
CourtBookinginformation.put("purpose",UPurpose);
CourtBookinginformation.put("date",UDate);
CourtBookinginformation.put("timeIn",UTimeStart);
CourtBookinginformation.put("timeOut",UTimeEnd);
CourtBookingDatabase.setValue(CourtBookinginformation);
Toast.makeText(getApplicationContext(),"Booking Successfull", Toast.LENGTH_LONG).show();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
});
}

Answer 1

If I'm not wrong I understand that you wanna update that field just if the data didn't exist, and if exists, do nothing.
In that case you should use an update call to update the database, in case that your data exists and equals the same data that you wanna push, the database will do nothing:
In case that you wanna avoid the writing in any case if the data already exist,, you should use a transaction. From the documentation:
When working with data that could be corrupted by concurrent modifications, such as incremental counters, you can use a transaction operation. You give this operation two arguments: an update function and an optional completion callback. The update function takes the current state of the data as an argument and returns the new desired state you would like to write. If another client writes to the location before your new value is successfully written, your update function is called again with the new current value, and the write is retried.
Using this, you will be able to read the data, check if it exists and do whatever you need depending if it exists or not.
You can read more about read and write data in Firebase in the next link from the official documentation:
https://firebase.google.com/docs/database/android/read-and-write