本篇主要介绍使用Mediaplayer实现mp3简易音乐播放器，程序运行界面如下

下面是代码实现，因为代码比较简单，注释已经比较明确了。

public class PlayActivity extends Activity implements OnClickListener {
	private EditText filenameText;
	// 音频播放的主要类
	private MediaPlayer mediaPlayer;
	private String filename;
	// 记录播放位置
	private int position;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		filenameText = (EditText) this.findViewById(R.id.filename);
		mediaPlayer = new MediaPlayer();
		Button playButton = (Button) this.findViewById(R.id.play);
		Button pauseButton = (Button) this.findViewById(R.id.pause);
		Button resetButton = (Button) this.findViewById(R.id.reset);
		Button stopButton = (Button) this.findViewById(R.id.stop);
		playButton.setOnClickListener(this);
		pauseButton.setOnClickListener(this);
		resetButton.setOnClickListener(this);
		stopButton.setOnClickListener(this);
	}

	//按钮点击事件
	@Override
	public void onClick(View v) {
		filename = filenameText.getText().toString();
		Button button = (Button) v;
		try {
			switch (v.getId()) {
			case R.id.play:
				play();
				break;

			case R.id.pause:
				if (mediaPlayer.isPlaying()) {
					mediaPlayer.pause();
					button.setText("继续");
				} else {
					mediaPlayer.start();
					button.setText("暂停");
				}
				break;

			case R.id.reset:
				//重播
				if (mediaPlayer.isPlaying()) {
					mediaPlayer.seekTo(0);
				} else {
					play();
				}
				break;

			case R.id.stop:
				//停止
				if (mediaPlayer.isPlaying())
					mediaPlayer.stop();
				break;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}

	}
	//当播放界面因为来电或者Home键进入后台调用，保存文件名与播放位置，便于恢复
	@Override
	protected void onSaveInstanceState(Bundle outState) {
		outState.putString("filename", filename);
		outState.putInt("position", position);
		super.onSaveInstanceState(outState);
	}
	
	//当界面进入后台被销毁，然后再次进入的时候被调用，在这里回复上次的播放状态
	@Override
	protected void onRestoreInstanceState(Bundle savedInstanceState) {
		this.filename = savedInstanceState.getString("filename");
		this.position = savedInstanceState.getInt("position");
		super.onRestoreInstanceState(savedInstanceState);
	}

	
	//当界面被遮挡，暂停播放
	@Override
	protected void onPause() {
		if (mediaPlayer.isPlaying()) {
			position = mediaPlayer.getCurrentPosition();
			mediaPlayer.stop();
		}
		super.onPause();
	}
	
	//当界面进入可交互状态，判断时候有文件名和播放记录，若有，则继续上次开始播放
	@Override
	protected void onResume() {
		if (position > 0 && filename != null) {
			try {
				play();
				mediaPlayer.seekTo(position);
				position = 0;
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		super.onResume();
	}

	//销毁资源
	@Override
	protected void onDestroy() {
		mediaPlayer.release();
		super.onDestroy();
	}
	
	//播放方法的核心实现
	private void play() throws IOException {
		//获取播放文件名
		File audioFile = new File(Environment.getExternalStorageDirectory(),
				filename);
		//重置状态
		mediaPlayer.reset();
		//设置数据源
		mediaPlayer.setDataSource(audioFile.getAbsolutePath());
		//进行前期硬件准备
		mediaPlayer.prepare();
		//开始播放
		mediaPlayer.start();
	}

	
}