Firestore - How to get document id after adding a document to a collection

Question

Is there a way to acquire the document id that was generated after adding a document to a collection?

If I add a document to a collection that represents a \"post\"

Answer 1

For Android, Java, you're suppose to get the Document ID before you set() or add() something to Firestore. Like so:

//Fields: 
CollectionReference toolsCollectionRef = FirebaseFirestore.getInstance().collection(toolsCollection);
CustomPOJO_Model toolToPost; 

//In Methods: 
String newDocID= toolsCollectionRef.document().getId();   //Get Doc ID first. 
toolToPost.setToolID(newDocID);

//Now use the doc ID:
toolsCollectionRef.document(newDocID).set(toolToPost.getConvertedTool_KeyValuePair ()).addOnCompleteListener(new OnCompleteListener() {
    @Override
    public void onComplete(@NonNull Task task) {
    }
});

//Re-use same ID in another post: 
usersCollectionRef.document(mAuth.getUid()).collection(usersToolsCollection).document(toolToPost.getToolID()).set(toolToPost.getConvertedTool_KeyValuePair());