<!--Permissions for internet-->
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--Button for playing audio-->
    <Button
        android:id="@+id/idBtnPlay"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Play Audio file"
        android:textAllCaps="false" />

    <!--Button for pausing the audio-->
    <Button
        android:id="@+id/idBtnPause"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/idBtnPlay"
        android:layout_centerInParent="true"
        android:text="Pause Audio"
        android:textAllCaps="false" />

</RelativeLayout>

import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    // creating a variable for
    // button and media player
    Button playBtn, pauseBtn;
    MediaPlayer mediaPlayer;

    // creating a string for storing
    // our audio url from firebase.
    String audioUrl;

    // creating a variable for our Firebase Database.
    FirebaseDatabase firebaseDatabase;

    // creating a variable for our 
    // Database Reference for Firebase.
    DatabaseReference databaseReference;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // below line is used to get the instance 
        // of our Firebase database.
        firebaseDatabase = FirebaseDatabase.getInstance();

        // below line is used to get reference for our database.
        databaseReference = firebaseDatabase.getReference("url");

        // calling add value event listener method for getting the values from database.
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                // this method is call to get the realtime updates in the data.
                // this method is called when the data is changed in our Firebase console.
                // below line is for getting the data from snapshot of our database.
                audioUrl = snapshot.getValue(String.class);
                // after getting the value for our audio url we are storing it in our string.
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                // calling on cancelled method when we receive any error or we are not able to get the data.
                Toast.makeText(MainActivity.this, "Fail to get audio url.", Toast.LENGTH_SHORT).show();
            }
        });

        // initializing our buttons
        playBtn = findViewById(R.id.idBtnPlay);
        pauseBtn = findViewById(R.id.idBtnPause);

        // setting on click listener for our play and pause buttons.
        playBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // calling method to play audio.
                playAudio(audioUrl);
            }
        });
        pauseBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // checking the media player 
                // if the audio is playing or not.
                if (mediaPlayer.isPlaying()) {
                    // pausing the media player if 
                    // media player is playing we are 
                    // calling below line to stop our media player.
                    mediaPlayer.stop();
                    mediaPlayer.reset();
                    mediaPlayer.release();

                    // below line is to display a message when media player is paused.
                    Toast.makeText(MainActivity.this, "Audio has been paused", Toast.LENGTH_SHORT).show();
                } else {
                    // this method is called when media player is not playing.
                    Toast.makeText(MainActivity.this, "Audio has not played", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    private void playAudio(String audioUrl) {
        // initializing media player
        mediaPlayer = new MediaPlayer();

        // below line is use to set the audio stream type for our media player.
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        try {
            // below line is use to set our 
            // url to our media player.
            mediaPlayer.setDataSource(audioUrl);

            // below line is use to prepare 
            // and start our media player.
            mediaPlayer.prepare();
            mediaPlayer.start();

            // below line is use to display a toast message.
            Toast.makeText(this, "Audio started playing..", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            // this line of code is use to handle error while playing our audio file.
            Toast.makeText(this, "Error found is " + e, Toast.LENGTH_SHORT).show();
        }
    }
}