Codice MediaRecorder e MediaPlayer

Salvo qui il codice completo di MediaRecorder e MediaPlayer:

public class MainActivity extends Activity{

 private MediaPlayer mPlayer;
 private MediaRecorder mRecorder;
 private Button bttRecord; 
 private Button bttStopRecord;
 private Button bttPlay;
 private Button bttStopPlay;
 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  bttRecord=(Button)findViewById(R.id.button1);
  bttStopRecord=(Button)findViewById(R.id.button2);
  bttPlay=(Button)findViewById(R.id.button3);
  bttStopPlay=(Button)findViewById(R.id.button4);
  
  bttRecord.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View v) {
    mRecorder =new MediaRecorder();
    mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    mRecorder.setOutputFile(Environment.getExternalStorageDirectory().getAbsolutePath()+"/mioFile.3gp");
    try{
     mRecorder.prepare();
    }catch(Exception e){
     Log.d("errore", "Prepare failed!");
    }
    mRecorder.start();
   }
  });
  bttStopRecord.setOnClickListener(new View.OnClickListener() {
   
   @Override
   public void onClick(View v) {
    mRecorder.stop();
    mRecorder.release();
    mRecorder=null;
    
   }
  });
  
  bttPlay.setOnClickListener(new View.OnClickListener() {
   
   @Override
   public void onClick(View v) {
    mPlayer=new MediaPlayer();
    try{
     mPlayer.setDataSource(Environment.getExternalStorageDirectory().getAbsolutePath()+"/mioFile.3gp");
     mPlayer.prepare();
     mPlayer.start();
    }catch(Exception e)
    {
     Log.d("Exception", "Play failed");
    }
    
   }
  });
  
  bttStopPlay.setOnClickListener(new View.OnClickListener() {
   
   @Override
   public void onClick(View v) {
    mPlayer.release();
    mPlayer=null;
    
   }
  });
  
 
 }

 
}

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.laboratorio.MainActivity" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="38dp"
        android:text="Record" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button1"
        android:layout_alignBottom="@+id/button1"
        android:layout_marginLeft="46dp"
        android:layout_toRightOf="@+id/button1"
        android:text="Stop record" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_below="@+id/button1"
        android:layout_marginTop="55dp"
        android:text="Play" />

    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button3"
        android:layout_alignBottom="@+id/button3"
        android:layout_alignLeft="@+id/button2"
        android:text="Stop Play" />

</RelativeLayout> 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.laboratorio"
    android:versionCode="1"
    android:versionName="1.0" >
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.RECORD_AUDIO" />
    <uses-sdk
        android:minSdkVersion="18"
        android:targetSdkVersion="18" />

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

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest> 

Per eventuale ripasso futuro.