java setAudioSource failed

Всем доброго времени суток! При написании пробного диктофона-проигрывателя(Приложение записывает аудио файл с микрофона и сохраняет его в формате.3gpp) столкнулся с такой проблемой: при запуске приложение крашится со следующей ошибкой:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.myapplication, PID: 5795
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.RuntimeException: setAudioSource failed.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2572)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2654)
        at android.app.ActivityThread.-wrap11(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1488)
        at android.os.Handler.dispatchMessage(Handler.java:111)
        at android.os.Looper.loop(Looper.java:207)
        at android.app.ActivityThread.main(ActivityThread.java:5728)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:679)
     Caused by: java.lang.RuntimeException: setAudioSource failed.
        at android.media.MediaRecorder.setAudioSource(Native Method)
        at com.example.myapplication.MainActivity.onCreate(MainActivity.java:33)
        at android.app.Activity.performCreate(Activity.java:6368)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1113)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2519)

Мой код приведён ниже

MainActivity.java

package com.example.myapplication;

import android.media.MediaPlayer;
import android.media.MediaRecorder;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private Button play, stop, record;
    private MediaRecorder myAudioRecorder;
    private String outputFile;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        play = (Button) findViewById(R.id.play);
        stop = (Button) findViewById(R.id.stop);
        record = (Button) findViewById(R.id.record);
        stop.setEnabled(false);
        play.setEnabled(false);
        outputFile = Environment.getExternalStorageDirectory().getAbsolutePath() + "/recording.3gp";
        myAudioRecorder = new MediaRecorder();
        myAudioRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        myAudioRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        myAudioRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
        myAudioRecorder.setOutputFile(outputFile);
        record.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    myAudioRecorder.prepare();
                    myAudioRecorder.start();
                } catch (IllegalStateException ise) {
                    // make something ...
                } catch (IOException ioe) {
                    // make something
                }
                record.setEnabled(false);
                stop.setEnabled(true);
                Toast.makeText(getApplicationContext(), "Recording started", Toast.LENGTH_LONG).show();
            }
        });

        stop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myAudioRecorder.stop();
                myAudioRecorder.release();
                myAudioRecorder = null;
                record.setEnabled(true);
                stop.setEnabled(false);
                play.setEnabled(true);
                Toast.makeText(getApplicationContext(), "Audio Recorder successfully", Toast.LENGTH_LONG).show();
            }
        });

        play.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MediaPlayer mediaPlayer = new MediaPlayer();
                try {
                    mediaPlayer.setDataSource(outputFile);
                    mediaPlayer.prepare();
                    mediaPlayer.start();
                    Toast.makeText(getApplicationContext(), "Playing Audio", Toast.LENGTH_LONG).show();
                } catch (Exception e) {
                    // make something
                }
            }
        });

    }


}

Разметка

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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">

    <Button
        android:id="@+id/record"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        android:text="Record"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/record"
        android:layout_centerHorizontal="true"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        android:text="Stop"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.356" />

    <Button
        android:id="@+id/play"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/stop"
        android:layout_centerHorizontal="true"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="8dp"
        android:text="Play"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.498"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.247" />
</android.support.constraint.ConstraintLayout>

AndroidManifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapplication">
    <uses-permission android:name="android.permission.RECORD_AUDIO"></uses-permission>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

В чём проблема? Где копать?