How to get value of some field in firebase firestore android?

The Cloud Firestore client-side SDKs always read and returns full documents. There is no way to read a subset of the fields in a document.

You can retrieve the entire document, and then process the DocumentSnapshot to just use the fields you're interested. But this means you're using more bandwidth than needed. If this is a regular occurrence for your app, consider creating a secondary collection where each document contains just the fields you're interested in.

Also see Doug's answer here (for Swift): How to access a specific field from Cloud FireStore Firebase in Swift

Firestore can read single field value. Firebase guides looks like didn't show these simple method.

For example:

[android]

String value = document.getString("col_1");


[node.js]

const value = doc.data().col_1