How to replace string-arrays with firestore references in Android Kotlin?

Issue

I am trying to build an autoTextView with a firestore connection.

I already built a working autoTextView application in which the data is saved directly in the strings.xml file. I also already connected firestore to my app.

What I am trying to do now is to replace this data frommy strings.xml file with a connection to firebase. So the user types something in in the autoTextView, the auto completion options should come from firebase and not from the strings.xml file.

Does anyone have an idea how I could try implementing that?

strings.xml:

<resources>
    <string name="app_name">servus</string>
    <string name="hint">Please type language...</string>
    <string name="submit">Submit</string>
    <string name="submitted_lang">Submitted language:</string>

    <string-array name="Languages">
        <item>Java</item>
        <item>Kotlin</item>
        <item>Swift</item>
        <item>Python</item>
        <item>Scala</item>
        <item>Perl</item>
        <item>Javascript</item>
        <item>Jquery</item>
    </string-array>

</resources>

MainActivity.kt file:

package com.example.servus

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import android.widget.TextView
import com.google.firebase.firestore.ktx.firestore
import com.google.firebase.ktx.Firebase

import android.view.View
import android.widget.ArrayAdapter
import android.widget.AutoCompleteTextView
import android.widget.Button
import android.widget.Toast


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val autotextView
                = findViewById<AutoCompleteTextView>(R.id.autoTextView)
        // Get the array of languages
        val languages
                = resources.getStringArray(R.array.Languages)
        // Create adapter and add in AutoCompleteTextView
        val adapter
                = ArrayAdapter(this,
            android.R.layout.simple_list_item_1, languages)
        autotextView.setAdapter(adapter)

        val button
                = findViewById<Button>(R.id.btn); if (button != null)
        {
            button ?.setOnClickListener(View.OnClickListener {
                val enteredText = getString(R.string.submitted_lang) + " " + autotextView.getText()
                Toast.makeText(this@MainActivity, enteredText, Toast.LENGTH_SHORT).show()
            })
        }
  }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <AutoCompleteTextView
        android:id="@+id/autoTextView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:hint="@string/hint"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.249" />

</androidx.constraintlayout.widget.ConstraintLayout>

Solution

When you get the languages, you need to fetch them from the firestore database instead of loading them from strings.xml. You can use the strings.xml values as a fall-back for if you're offline, for example.

Reading a document from firestore:

// This code goes in your DatabaseManger or whatever class in your android app your handling firestore
// Figure out the appropriate document path based on the DB schema you designed
val docRef = db.collection("collection_name").document("document_name")
docRef.get()
        .addOnSuccessListener { document ->
            if (document != null) {
                Log.d(TAG, "DocumentSnapshot data: ${document.data}")
                // Here's your languages, save them somewhere so you can use them
            } else {
                Log.d(TAG, "No such document")
            }
        }
        .addOnFailureListener { exception ->
            Log.d(TAG, "get failed with ", exception)
            // Probably offline, or auth problem. Maybe use strings.xml backup.
        }

This is an asynchronous operation and may take a couple of seconds. You should think what to show to the user in the meantime while they wait. Future times should use the local Firestore cache to avoid the wait. Read more about the Firestore Android SDK to learn how to use it.

Answered By - Can_of_awe