試圖創建從soundcloud播放歌曲的媒體播放器。

Question

我想創建具有前進，後退，播放，暫停按鈕的媒體播放器。從SoundCloud.com播放歌曲。這裏是我的代碼..

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    b1 = (Button) findViewById(R.id.button); 
    b2 = (Button) findViewById(R.id.button2); 
    b3 = (Button) findViewById(R.id.button3); 
    b4 = (Button) findViewById(R.id.button4); 

    seekbar = (SeekBar) findViewById(R.id.seekBar); 

    mp = new MediaPlayer(); 
    seekbar.setVisibility(SeekBar.VISIBLE); 
    seekbar.setProgress(0); 
    seekbar.setMax(mp.getDuration()); 

    mp.setAudioStreamType(AudioManager.STREAM_MUSIC); 

    mp.setOnPreparedListener(new MediaPlayer.OnPreparedListener() { 
     @Override 
     public void onPrepared(MediaPlayer player) { 
      mp.start(); 

     } 
    }); 

    b2.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 

      Toast.makeText(getApplicationContext(), "Playing sound", Toast.LENGTH_SHORT).show(); 
      mp.start(); 

      finalTime = mp.getDuration(); 
      startTime = mp.getCurrentPosition(); 

      if (oneTimeOnly == 0) { 
       seekbar.setMax((int) finalTime); 
       oneTimeOnly = 1; 
      } 
      seekbar.setProgress((int) startTime); 
      myHandler.postDelayed(UpdateSongTime, 100); 
      b2.setEnabled(true); 
      b3.setEnabled(false); 
     } 
    }); 

    b3.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      if (mp.isPlaying()) { 
       Toast.makeText(getApplicationContext(), "Pausing sound", Toast.LENGTH_SHORT).show(); 
       mp.pause(); 
       mp.seekTo(0); 
      } 

      b2.setEnabled(false); 
      b3.setEnabled(true); 
     } 
    }); 
      b1.setOnClickListener(new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 
        int temp = (int) startTime; 

        if ((temp + forwardTime) <= finalTime) { 
         startTime = startTime + forwardTime; 
         mp.seekTo((int) startTime); 
         Toast.makeText(getApplicationContext(), "You have Jumped forward 5 seconds", Toast.LENGTH_SHORT).show(); 
        } else { 
         Toast.makeText(getApplicationContext(), "Cannot jump forward 5 seconds", Toast.LENGTH_SHORT).show(); 
        } 
       } 
      }); 
    b4.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      int temp = (int) startTime; 

      if ((temp - backwardTime) > 0) { 
       startTime = startTime - backwardTime; 
       mp.seekTo((int) startTime); 
       Toast.makeText(getApplicationContext(), "You have Jumped backward 5 seconds", Toast.LENGTH_SHORT).show(); 
      } else { 
       Toast.makeText(getApplicationContext(), "Cannot jump backward 5 seconds", Toast.LENGTH_SHORT).show(); 
      } 
     } 
    }); 
    mListItems = new ArrayList<Track>(); 
    final ListView listView = (ListView)findViewById(R.id.listview); 
    mAdapter = new SCTrackAdapter(this, mListItems); 
    listView.setAdapter(mAdapter); 
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
      Track track = mListItems.get(position); 
      if (mp.isPlaying()) { 
       mp.stop(); 
       mp.reset(); 
      } 

      try { 
       mp.setDataSource(track.getStreamURL() + "?client_id=" + Config.CLIENT_ID); 
       mp.prepareAsync(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 

     } 
    }); 

    SCService scService = SoundCloud.getService(); 
    scService.getRecentTracks(new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(new Date()), new Callback<List<Track>>() { 
     @Override 
     public void success(List<Track> tracks, Response response) { 
      loadTracks(tracks); 
     } 

     @Override 
     public void failure(RetrofitError error) { 
      Log.d(TAG, "Error: " + error); 
     } 
    }); 
} 
private void loadTracks(List<Track> tracks) { 
    mListItems.clear(); 
    mListItems.addAll(tracks); 
    mAdapter.notifyDataSetChanged(); 
} 
private Runnable UpdateSongTime = new Runnable() { 
public void run() { 
    startTime = mp.getCurrentPosition(); 
    seekbar.setProgress((int)startTime); 
    myHandler.postDelayed(this, 100); 
} 
}; 

@Override 
public void onDestroy() { 
    super.onDestroy(); 
    mp.release();if (mp != null) { 
     if (mp.isPlaying()) { 
      mp.stop(); 
         } 
     mp.release(); 
     mp = null; 
    } 
} 

我也加入了AndroidMenifest。

<permission android:name="android.permission.INTERNET" /> 
<uses-permission android:name="android.permission.INTERNET" /> 
<permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 

和我分別創建類配置，SCService，SCTrackAdapter，SounndCloude，軌道..我按照代碼從該網站 「http://www.sitepoint.com/develop-music-streaming-android-app」。 但我得到錯誤。

01-07 14:59:46.055 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: Attempt to call getDuration without a valid mediaplayer 
    01-07 14:59:46.055 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: error (-38, 0) 
    01-07 14:59:46.276 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: Error (-38,0) 
    01-07 14:59:46.895 25541-25547/com.vetecstech.www.mediap E/MediaPlayer: error (1, -1004) 
    01-07 14:59:47.215 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: Error (1,-1004) 
    01-07 14:59:50.855 25541-25543/com.vetecstech.www.mediap D/dalvikvm: GC_CONCURRENT freed 1429K, 58% free 3082K/7175K, external 5368K/6641K, paused 4ms+4ms 
    01-07 14:59:53.035 25541-25546/com.vetecstech.www.mediap I/dalvikvm: Jit: resizing JitTable from 512 to 1024 

當我點擊列表項目時，我得到錯誤。錯誤在下面。

01-07 15:19:41.765 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: Error (1,-2147483648) 
01-07 15:19:45.335 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: start called in state 0 
    01-07 15:19:45.335 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: error (-38, 0) 
    01-07 15:19:45.335 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: Attempt to call getDuration without a valid mediaplayer 
    01-07 15:19:45.335 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: error (-38, 0) 

請幫助我。無法理解問題出在哪裏。

Answer 1

mp = new MediaPlayer(); 
... 
seekbar.setMax(mp.getDuration()); 

你試圖讓毫無準備的MediaPlayer的持續時間，這是造成問題

01-07 14:59:46.055 25541-25541/com.vetecstech.www.mediap E/MediaPlayer: Attempt to call getDuration without a valid mediaplayer 

您可能需要移動seekbar.setMax(mp.getDuration());您OnPreparedListener內

mp.setOnPreparedListener(new MediaPlayer.OnPreparedListener() { 
    @Override 
    public void onPrepared(MediaPlayer player) { 
     seekbar.setMax(mp.getDuration()); 
     mp.start(); 

    } 
});