Android媒体开发之音乐播放器

package com.example.musicplay; 
import java.io.File; 
import android.app.Activity; 
import android.content.Context; 
import android.media.MediaPlayer; 
import android.media.MediaPlayer.OnPreparedListener; 
import android.os.Bundle; 
import android.os.Environment; 
import android.telephony.PhoneStateListener; 
import android.telephony.TelephonyManager; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.Toast; 
public class MainActivity extends Activity { 
 private EditText nameText; 
 private String path; 
 private int position; 
 private MediaPlayer mediaplayer; 
 private boolean pause; 
 protected void onCreate(Bundle savedInstanceState) { 
 super.onCreate(savedInstanceState); 
 setContentView(R.layout.activity_main); 
 nameText=(EditText) this.findViewById(R.id.filename); 
 mediaplayer=new MediaPlayer(); 
 
 } 
  
 //以下方法会造成只要应用在后台音乐都会停止播放 
 @Override 
 //当应用不在前台时，停止播放 
 protected void onPause() { 
 if(mediaplayer.isPlaying()){ 
  position=mediaplayer.getCurrentPosition(); 
  mediaplayer.stop(); 
 } 
 super.onPause(); 
 } 
  
 @Override 
 protected void onResume() { 
 if(position>0&&path!=null){ 
  play(); 
  mediaplayer.seekTo(position); 
  position=0; 
 } 
 super.onResume(); 
 } 
 @Override 
 protected void onDestroy() { 
 mediaplayer.release(); 
 mediaplayer=null; 
 super.onDestroy(); 
 } 
 public void mediaplay(View v){ 
 switch (v.getId()) { 
 case R.id.playbutton: 
  String filename=nameText.getText().toString(); 
  //Environment.getExternalStorageDirectory()检查外部存储设备的可用性 
  File audio=new File(Environment.getExternalStorageDirectory(),filename); 
  if(audio.exists()){ 
  //获取SDCard目录,2.2的时候为:/mnt/sdcart 2.1的时候为：/sdcard，所以使用静态方法得到路径会好一点。   
  path=audio.getAbsolutePath(); 
  play(); 
  } 
  else{ 
  path=null; 
  Toast.makeText(getApplicationContext(), R.string.error, 1).show(); 
  } 
  break; 
   
 case R.id.pausebutton: 
  if(mediaplayer.isPlaying()){ 
  mediaplayer.pause(); 
  pause=true; 
  ((Button)v).setText(R.string.continues); 
  }else{ 
  if(pause){ 
   mediaplayer.start(); 
   pause=false; 
   ((Button)v).setText(R.string.pausebutton); 
  } 
  } 
  break; 
   
 case R.id.resetbutton: 
  if(mediaplayer.isPlaying()){ 
  mediaplayer.seekTo(0);//从开始位置播放 
  }else{ 
  if(path!=null){ 
   play(); 
  } 
  } 
  break; 
   
 case R.id.stopbutton: 
  if(mediaplayer.isPlaying()){ 
  mediaplayer.stop(); 
  } 
  break; 
   
 default: 
  break; 
 } 
 } 
 private void play() { 
 try { 
  mediaplayer.reset();//把各项参数恢复到初始化状态 
  mediaplayer.setDataSource(path); 
  mediaplayer.prepare();//进行缓冲 
  //设置缓冲监听器 
  mediaplayer.setOnPreparedListener(new OnPreparedListener() { 
   
  //缓冲完毕后调用onPrepared方法 
  public void onPrepared(MediaPlayer mp) { 
   // 里面写缓冲完要干的事 
   mediaplayer.start(); 
  } 
  }); 
 } catch (Exception e) { 
  e.printStackTrace(); 
 } 
 } 
}