Read data from Cloud Firestore in Android

In this tutorial, you will see how to fetch data from Cloud Firestore and use it in your android application.

Prerequisites

Before you start this tutorial make sure you have:

• Android Studio 3.0 or higher
• An Android device or an emulator

Create a Firebase Project

Create an android project as usual.

Sign in to your google account in android studio.

Here’s an example of collection you wish to fetch data from:

Let us suppose you want to inflate your data onto this kind of layout:

Profile for a Doctor

First you need to define an instance of your database.

public class Test extends AppCompatActivity {
    private FirebaseFirestore yourDB;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test);
        yourDB = FirebaseFirestore.getInstance();
    }

Next, you need to define instance of the collection you want to fetch details from. It’s optional to do this inside any method according to your convenience.

@Override
public void onStart(){
    super.onStart();
    
    yourDB.collection("Doctors")
          .document("abc@xyz.com")
          .get()
          .addOnCompleteListener
          (new OnCompleteListener<DocumentSnapshot>() {
        
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        
        if(task.isSuccessful()){
            DocumentSnapshot doc = task.getResult();
           
            //set name next to Name TextView
            (editText1.setText(doc.getString("Name"));
            
            //set email next to Email TextView
            (editText2.setText(doc.getString("Email"));
            //convert contact field from number to String               
            //set contact next to Contact TextView
            (editText3.setText(doc.getLong("Contact").toString());
            
            //similarly get all the other fields}
        }
    })
    .addOnFailureListener(new OnFailureListener() {
        
        @Override
        public void onFailure(@NonNull Exception e) {
            //print e.message();
        }
    });
}

Here, the methods used have following functionalities:

• .addOnCompleteListener( OnCompleterListener<TResult> listener ): Adds a listener that is called when the Task completes. The listener will be called on main application thread. If the Task is already complete, a call to the listener will be immediately scheduled. If multiple listeners are added, they will be called in the order in which they were added.
• <DocumentSnapshot>: It contains data read from a document in your Cloud Firestore database. The data can be extracted with the getData () or get(string) methods.
• onComplete( Task<TResult> task ): Called when the Task completes.
• .addOnFailureListener( OnFailureListener listener ): Adds a listener that is called if the Task fails. The listener will be called on main application thread. If the Task has already failed, a call to the listener will be immediately scheduled. If multiple listeners are added, they will be called in the order in which they were added.
• TResult getResult(): Gets the result of the Task, if it has already completed.
• Boolean isSuccessful(): Returns true if the Task has completed successfully; false otherwise.