Slide 11.8: Writing data to Firebase

Writing Data to Firebase

The CRUD operations on Firebase are given in the following slides:

Create: Writing data to Firebase,
Read: Reading data from Firebase,
Update: Updating data in Firebase, and
Delete: Deleting data from Firebase.

Firebase data is written to a Firebase Database reference and retrieved by attaching an asynchronous listener to the reference. The listener is triggered once for the initial state of the data and again anytime the data changes. To read or write data from the database, an instance of DatabaseReference is needed:

 private DatabaseReference mDatabase;
 // ...
 mDatabase = FirebaseDatabase.getInstance( ).getReference( );

For basic write operations, you can use setValue() to save data to a specified reference, replacing any existing data at that path. For example, the code below inserts a node called “app_title” in JSON top level:

 DatabaseReference mRef = mDatabase.getReference( "app_title" );
mRef.setValue( "Realtime Database" );

You can use this method setValue() to:

Pass types that correspond to the available JSON types: String, Long, Double, Boolean, Map<String, Object>, or List<Object>,

Pass a custom Java object, if the class that defines it has a default constructor that takes no arguments and has public getters for the properties to be assigned. If you use a Java object, the contents of your object are automatically mapped to child locations in a nested fashion.