怎么在Android中利用SeekBar实现音乐播放器功能

package my.com.mymusicp;

import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.IBinder;
import android.os.Message;
import android.os.RemoteException;
import android.support.annotation.Nullable;
import android.util.Log;

import java.io.IOException;
import java.util.Timer;
import java.util.TimerTask;

/**
 * Created by c_ljf on 16-12-26.
 */
public class MyMusicService extends Service {
  private String tag="MyMusicService";
  private MediaPlayer mediaPlayer;

  @Override
  public void onCreate() {
    super.onCreate();
    mediaPlayer = new MediaPlayer();
  }

  @Nullable
  @Override
  public IBinder onBind(Intent intent) {
    return new MyMusicBinder();
  }
  class MyMusicBinder extends IMyMusicService.Stub{

    @Override
    public void play() throws RemoteException {
      playmusic();
    }

    @Override
    public void pause() throws RemoteException {
     pausemusic();
    }

    @Override
    public void stop() throws RemoteException {
      stopmusic();
    }

    @Override
    public void continuePlay() throws RemoteException {
      rePlayMusic();
    }

    @Override
    public void seekPlayProgress(int position) throws RemoteException {
      seekPlayPositiom(position);
    }

  }
  //播放音乐
  public void playmusic(){
    mediaPlayer.reset();
    String url = "sdcard/Music/Fade.mp3";
    Log.i(tag,url);
    try {
      mediaPlayer.setDataSource(url);
      mediaPlayer.prepare();
    } catch (IOException e) {
      e.printStackTrace();
    }
     // might take long! (for buffering, etc)
    mediaPlayer.start();
    //更新播放进度条
    seekPlayProgress();
  }
  public void pausemusic(){
    mediaPlayer.pause();
    Log.i(tag,"暂停播放");

  }

  public void stopmusic(){
    mediaPlayer.reset();
    Log.i(tag,"停止播放");
    mediaPlayer.stop();
  }

  @Override
  public void onDestroy() {
    super.onDestroy();
  }
  public void seekPlayPositiom(int positon){
    Log.i(tag,"设置播放位置");
    mediaPlayer.seekTo(positon);
  }


  public void seekPlayProgress(){
     /*1.获取当前歌曲的总时长*/
    final int duration=mediaPlayer.getDuration();

    //计时器对象
    final Timer timer=new Timer();
    final TimerTask task=new TimerTask() {
      @Override
      public void run() {
        //开启线程定时获取当前播放进度
        int currentposition=mediaPlayer.getCurrentPosition();
        //利用message给主线程发消息更新seekbar进度
        Message ms=Message.obtain();
        Bundle bundle=new Bundle();
        bundle.putInt("duration",duration);
        Log.i(tag,"歌曲总长度"+duration);
        bundle.putInt("currentposition",currentposition);
        Log.i(tag,"当前长度"+currentposition);
        //设置发送的消息内容
        ms.setData(bundle);
        //发送消息
        MainActivity.handler.sendMessage(ms);
      }
    };
     timer.schedule(task,300,500);
    //当播放结束时停止播放
    mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
      @Override
      public void onCompletion(MediaPlayer mp) {
        Log.i(tag,"取消计时任务");
        timer.cancel();
        task.cancel();
      }
    });

  }
  public void rePlayMusic() {
    Log.i(tag, "继续播放音乐");
    mediaPlayer.start();
  }
}

package my.com.mymusicp;

import android.Manifest;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.os.RemoteException;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;

public class MainActivity extends AppCompatActivity {
  private IMyMusicService iMyMusicService;
  private static SeekBar seekBar;
  private Button btpause_play;
  private boolean b=true;//判断暂停和继续播放
  public static Handler handler=new Handler(){
    @Override
    public void handleMessage(Message msg) {
      //处理消息
      Bundle bundle=msg.getData();
      //获取歌曲长度和当前播放位置，并设置到进度条上
      int duration=bundle.getInt("duration");
      int currentposition=bundle.getInt("currentposition");
      seekBar.setMax(duration);
      seekBar.setProgress(currentposition);
    }
  };

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    verifyStoragePermissions(MainActivity.this);
    //获取播放暂停按钮
    btpause_play=(Button) findViewById(R.id.bt_pause);
    Intent intent=new Intent(MainActivity.this,MyMusicService.class);
    bindService(intent,new MyConn(),BIND_AUTO_CREATE);
    seekBar=(SeekBar) findViewById(R.id.seekBar);
    seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
      @Override
      public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
      }
      @Override
      public void onStartTrackingTouch(SeekBar seekBar) {
      }
      @Override
      public void onStopTrackingTouch(SeekBar seekBar) {
        try {
          iMyMusicService.seekPlayProgress(seekBar.getProgress());
        } catch (RemoteException e) {
          e.printStackTrace();
        }
      }
    });
  }
   //定义服务连接类
  class MyConn implements ServiceConnection{

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
      iMyMusicService=IMyMusicService.Stub.asInterface(service);
    }
    @Override
    public void onServiceDisconnected(ComponentName name) {

    }
  }
  public void play(View v){
    try {
      iMyMusicService.play();

    } catch (RemoteException e) {
      e.printStackTrace();
    }
  }

  public void pause(View v){
    try {
      if(b)
      {
       iMyMusicService.pause();
        b=false;
        btpause_play.setText("继续播放");
      }
      else{
         b=true;
        iMyMusicService.continuePlay();
        btpause_play.setText("暂停播放");

      }

    } catch (RemoteException e) {
      e.printStackTrace();
    }
  }

  public void stop(View v){
    try {
        iMyMusicService.stop();
    } catch (RemoteException e) {
      e.printStackTrace();
    }
  }
  // Storage Permissions
  private static final int REQUEST_EXTERNAL_STORAGE = 1;
  private static String[] PERMISSIONS_STORAGE = {
      Manifest.permission.READ_EXTERNAL_STORAGE,
      Manifest.permission.WRITE_EXTERNAL_STORAGE,
  };

  /**
   * Checks if the app has permission to write to device storage
   *
   * If the app does not has permission then the user will be prompted to grant permissions
   *
   * @param activity
   */
  public static void verifyStoragePermissions(Activity activity) {
    // Check if we have write permission
    int permission = ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);

    if (permission != PackageManager.PERMISSION_GRANTED) {
      // We don't have permission so prompt the user
      ActivityCompat.requestPermissions(
          activity,
          PERMISSIONS_STORAGE,
          REQUEST_EXTERNAL_STORAGE
      );
    }
  }
} 

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<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:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  android:paddingBottom="@dimen/activity_vertical_margin"
  tools:context="my.com.mymusicp.MainActivity">

  <LinearLayout
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:id="@+id/linearLayout">

    <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_weight="1"
      android:text="开始播放"
      android:onClick="play"
      android:id="@+id/bt_start"/>

    <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="暂停播放"
      android:layout_weight="1"
      android:onClick="pause"
      android:id="@+id/bt_pause"/>

    <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_weight="1"
      android:text="停止播放"
      android:onClick="stop"
      android:id="@+id/bt_stop"/>
  </LinearLayout>

  <SeekBar
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/seekBar"
    android:layout_below="@+id/linearLayout"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"/>

</RelativeLayout> 

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="my.com.mymusicp">
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
  <application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    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>
    <service android:name=".MyMusicService"/>
  </application>

</manifest>