Play mp3 in SD Card, using Android's MediaPlayer

In the exercise "Android MediaPlayer", the application play mp3 file in /res/raw folder. In this exercise, it will be modified to play a mp3 file, named music.mp3, in SD Card.

First of all, copy a mp3 file (music.mp3) to SD Card. Refer to the article "Create SD Card in Android Emulator and copy files into, in Eclipse, Emulator and DDMS" to copy mp3 file to SD Card.

main.xm have no change, refer to the exercise "Android MediaPlayer".

AndroidMediaPlayer.java

package com.exercise.AndroidMediaPlayer;

import java.io.IOException;

import android.app.Activity;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class AndroidMediaPlayer extends Activity {
 
 MediaPlayer mediaPlayer;
 Button buttonPlayPause, buttonQuit;
 TextView textState;
 
 private int stateMediaPlayer;
 private final int stateMP_Error = 0;
 private final int stateMP_NotStarter = 1;
 private final int stateMP_Playing = 2;
 private final int stateMP_Pausing = 3;
 
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
       buttonPlayPause = (Button)findViewById(R.id.playpause);
       buttonQuit = (Button)findViewById(R.id.quit);
       textState = (TextView)findViewById(R.id.state);
      
       buttonPlayPause.setOnClickListener(buttonPlayPauseOnClickListener);
       buttonQuit.setOnClickListener(buttonQuitOnClickListener);
      
       initMediaPlayer();
      
   }
  
   private void initMediaPlayer()
   {
    String PATH_TO_FILE = "/sdcard/music.mp3";    
    mediaPlayer = new  MediaPlayer();
    
    try {
   mediaPlayer.setDataSource(PATH_TO_FILE);
   mediaPlayer.prepare();
   Toast.makeText(this, PATH_TO_FILE, Toast.LENGTH_LONG).show();
   stateMediaPlayer = stateMP_NotStarter;
         textState.setText("- IDLE -");
  } catch (IllegalArgumentException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
   Toast.makeText(this, e.toString(), Toast.LENGTH_LONG).show();
   stateMediaPlayer = stateMP_Error;
         textState.setText("- ERROR!!! -");
  } catch (IllegalStateException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
   Toast.makeText(this, e.toString(), Toast.LENGTH_LONG).show();
   stateMediaPlayer = stateMP_Error;
         textState.setText("- ERROR!!! -");
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
   Toast.makeText(this, e.toString(), Toast.LENGTH_LONG).show();
   stateMediaPlayer = stateMP_Error;
         textState.setText("- ERROR!!! -");
  }
   }
  
   Button.OnClickListener buttonPlayPauseOnClickListener
    = new Button.OnClickListener(){

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    switch(stateMediaPlayer){
    case stateMP_Error:
     break;
    case stateMP_NotStarter:
     mediaPlayer.start();
     buttonPlayPause.setText("Pause");
     textState.setText("- PLAYING -");
     stateMediaPlayer = stateMP_Playing;
     break;
    case stateMP_Playing:
     mediaPlayer.pause();
     buttonPlayPause.setText("Play");
     textState.setText("- PAUSING -");
     stateMediaPlayer = stateMP_Pausing;
     break;
    case stateMP_Pausing:
     mediaPlayer.start();
     buttonPlayPause.setText("Pause");
     textState.setText("- PLAYING -");
     stateMediaPlayer = stateMP_Playing;
     break;
    }
    
   }
   };
  
   Button.OnClickListener buttonQuitOnClickListener
 = new Button.OnClickListener(){

  @Override
  public void onClick(View v) {
   // TODO Auto-generated method stub
   mediaPlayer.stop();
   mediaPlayer.release();
   finish();
  } 
   };
}

Download the files.

Updated@2016-06-18:
- Open mp3 using Intent.ACTION_OPEN_DOCUMENT, ACTION_GET_CONTENT and ACTION_PICK, with checking and requesting permission at runtime.