如何从SherlockFragment获取上下文并开始活动

Question

使用swipable选项卡的动作栏Sherlock和在我的其中一个选项卡中，我指出它的内容为xml文件.... 有一个按钮“btnPlaylist”打开一个新的活动/意图，但突出显示的错误是在“上下文”，说它不能被解析成一个变量。

继承人的代码

public class Playback extends SherlockFragment implements OnCompletionListener, SeekBar.OnSeekBarChangeListener { 

    private ImageButton btnPlay; 
    private ImageButton btnForward; 
    private ImageButton btnBackward; 
    private ImageButton btnNext; 
    private ImageButton btnPlaylist; 
    private ImageButton btnPrevious; 
    private ImageButton btnRepeat; 
    private ImageButton btnShuffle; 
    private SeekBar songProgressBar; 
    private TextView songTitleLabel; 
    private TextView songCurrentDurationLabel; 
    private TextView songTotalDurationLabel; 
    // Media Player 
    private MediaPlayer mp; 
    // Handler to update UI timer, progress bar etc,. 
    private Handler mHandler = new Handler();; 
    private SongsManager songManager; 
    private Utilities utils; 
    private int seekForwardTime = 5000; // 5000 milliseconds 
    private int seekBackwardTime = 5000; // 5000 milliseconds 
    private int currentSongIndex = 0; 
    private boolean isShuffle = false; 
    private boolean isRepeat = false; 
    private ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>(); 


    @Override 
    public SherlockFragmentActivity getSherlockActivity() { 
     return super.getSherlockActivity(); 
    } 

    @Override 
    public void onViewCreated(View view, Bundle savedInstanceState) { 
     super.onViewCreated(view, savedInstanceState); 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
      Bundle savedInstanceState) { 
     View view = inflater.inflate(R.layout.player, container, false); 
     btnPlay = (ImageButton) view.findViewById(R.id.btnPlay); 
     btnForward = (ImageButton) view.findViewById(R.id.btnForward); 
     btnBackward = (ImageButton) view.findViewById(R.id.btnBackward); 
     btnNext = (ImageButton) view.findViewById(R.id.btnNext); 
     btnPrevious = (ImageButton) view.findViewById(R.id.btnPrevious); 
     btnPlaylist = (ImageButton) view.findViewById(R.id.btnPlaylist); 
     btnRepeat = (ImageButton) view.findViewById(R.id.btnRepeat); 
     btnShuffle = (ImageButton) view.findViewById(R.id.btnShuffle); 
     songProgressBar = (SeekBar) view.findViewById(R.id.songProgressBar); 
     songTitleLabel = (TextView) view.findViewById(R.id.songTitle); 
     songCurrentDurationLabel = (TextView) view.findViewById(R.id.songCurrentDurationLabel); 
     songTotalDurationLabel = (TextView) view.findViewById(R.id.songTotalDurationLabel); 

     mp = new MediaPlayer(); 
     songManager = new SongsManager(); 
     utils = new Utilities(); 

     // Listeners 
     songProgressBar.setOnSeekBarChangeListener(this); // Important 
     mp.setOnCompletionListener(this); // Important 

     // Getting all songs list 
     songsList = songManager.getPlayList(); 

     // By default play first song 
     playSong(0); 

     /** 
     * Play button click event 
     * plays a song and changes button to pause image 
     * pauses a song and changes button to play image 
     * */ 
     btnPlay.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       // check for already playing 
       if(mp.isPlaying()){ 
        if(mp!=null){ 
         mp.pause(); 
         // Changing button image to play button 
         btnPlay.setImageResource(R.drawable.btn_play); 
        } 
       }else{ 
        // Resume song 
        if(mp!=null){ 
         mp.start(); 
         // Changing button image to pause button 
         btnPlay.setImageResource(R.drawable.btn_pause); 
        } 
       } 

      } 
     }); 

     /** 
     * Forward button click event 
     * Forwards song specified seconds 
     * */ 
     btnForward.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       // get current song position     
       int currentPosition = mp.getCurrentPosition(); 
       // check if seekForward time is lesser than song duration 
       if(currentPosition + seekForwardTime <= mp.getDuration()){ 
        // forward song 
        mp.seekTo(currentPosition + seekForwardTime); 
       }else{ 
        // forward to end position 
        mp.seekTo(mp.getDuration()); 
       } 
      } 
     }); 

     /** 
     * Backward button click event 
     * Backward song to specified seconds 
     * */ 
     btnBackward.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       // get current song position     
       int currentPosition = mp.getCurrentPosition(); 
       // check if seekBackward time is greater than 0 sec 
       if(currentPosition - seekBackwardTime >= 0){ 
        // forward song 
        mp.seekTo(currentPosition - seekBackwardTime); 
       }else{ 
        // backward to starting position 
        mp.seekTo(0); 
       } 

      } 
     }); 

     /** 
     * Next button click event 
     * Plays next song by taking currentSongIndex + 1 
     * */ 
     btnNext.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       // check if next song is there or not 
       if(currentSongIndex < (songsList.size() - 1)){ 
        playSong(currentSongIndex + 1); 
        currentSongIndex = currentSongIndex + 1; 
       }else{ 
        // play first song 
        playSong(0); 
        currentSongIndex = 0; 
       } 

      } 
     }); 

     /** 
     * Back button click event 
     * Plays previous song by currentSongIndex - 1 
     * */ 
     btnPrevious.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       if(currentSongIndex > 0){ 
        playSong(currentSongIndex - 1); 
        currentSongIndex = currentSongIndex - 1; 
       }else{ 
        // play last song 
        playSong(songsList.size() - 1); 
        currentSongIndex = songsList.size() - 1; 
       } 

      } 
     }); 

     /** 
     * Button Click event for Repeat button 
     * Enables repeat flag to true 
     * */ 
     btnRepeat.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View view) { 
       if(isRepeat){ 
        isRepeat = false; 
        //Toast.makeText(this, "Repeat is OFF", Toast.LENGTH_SHORT).show(); 
        btnRepeat.setImageResource(R.drawable.btn_repeat); 
       }else{ 
        // make repeat to true 
        isRepeat = true; 
        //Toast.makeText(getApplicationContext(), "Repeat is ON", Toast.LENGTH_SHORT).show(); 
        // make shuffle to false 
        isShuffle = false; 
        btnRepeat.setImageResource(R.drawable.btn_repeat_focused); 
        btnShuffle.setImageResource(R.drawable.btn_shuffle); 
       } 
      } 
     }); 

     /** 
     * Button Click event for Shuffle button 
     * Enables shuffle flag to true 
     * */ 
     btnShuffle.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       if(isShuffle){ 
        isShuffle = false; 
        //Toast.makeText(getApplicationContext(), "Shuffle is OFF", Toast.LENGTH_SHORT).show(); 
        btnShuffle.setImageResource(R.drawable.btn_shuffle); 
       }else{ 
        // make repeat to true 
        isShuffle= true; 
        //Toast.makeText(getApplicationContext(), "Shuffle is ON", Toast.LENGTH_SHORT).show(); 
        // make shuffle to false 
        isRepeat = false; 
        btnShuffle.setImageResource(R.drawable.btn_shuffle_focused); 
        btnRepeat.setImageResource(R.drawable.btn_repeat); 
       } 
      } 
     }); 

     /** 
     * Button Click event for Play list click event 
     * Launches list activity which displays list of songs 
     * */ 
     btnPlaylist.setOnClickListener(new View.OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       Intent i = new Intent(context, PlayListActivity.class); 
      } 
     }); 

     return view; 
    } 

    @Override 
    public void onSaveInstanceState(Bundle outState) { 
     super.onSaveInstanceState(outState); 
     setUserVisibleHint(true); 
    } 



    /** 
    * Receiving song index from playlist view 
    * and play the song 
    * */ 
    @Override 
    public void onActivityResult(int requestCode, 
            int resultCode, Intent data) { 
     super.onActivityResult(requestCode, resultCode, data); 
     if(resultCode == 100){ 
      currentSongIndex = data.getExtras().getInt("songIndex"); 
      // play selected song 
      playSong(currentSongIndex); 
     } 

    } 

    /** 
    * Function to play a song 
    * @param songIndex - index of song 
    * */ 
    public void playSong(int songIndex){ 
     // Play song 
     try { 
      mp.reset(); 
      mp.setDataSource(songsList.get(songIndex).get("songPath")); 
      mp.prepare(); 
      mp.start(); 
      // Displaying Song title 
      String songTitle = songsList.get(songIndex).get("songTitle"); 
      songTitleLabel.setText(songTitle); 

      // Changing Button Image to pause image 
      btnPlay.setImageResource(R.drawable.btn_pause); 

      // set Progress bar values 
      songProgressBar.setProgress(0); 
      songProgressBar.setMax(100); 

      // Updating progress bar 
      updateProgressBar();    
     } catch (IllegalArgumentException e) { 
      e.printStackTrace(); 
     } catch (IllegalStateException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
    } 

    /** 
    * Update timer on seekbar 
    * */ 
    public void updateProgressBar() { 
     mHandler.postDelayed(mUpdateTimeTask, 100);   
    } 

    /** 
    * Background Runnable thread 
    * */ 
    private Runnable mUpdateTimeTask = new Runnable() { 
      public void run() { 
       long totalDuration = mp.getDuration(); 
       long currentDuration = mp.getCurrentPosition(); 

       // Displaying Total Duration time 
       songTotalDurationLabel.setText(""+utils.milliSecondsToTimer(totalDuration)); 
       // Displaying time completed playing 
       songCurrentDurationLabel.setText(""+utils.milliSecondsToTimer(currentDuration)); 

       // Updating progress bar 
       int progress = (int)(utils.getProgressPercentage(currentDuration, totalDuration)); 
       //Log.d("Progress", ""+progress); 
       songProgressBar.setProgress(progress); 

       // Running this thread after 100 milliseconds 
       mHandler.postDelayed(this, 100); 
      } 
     }; 

    /** 
    * 
    * */ 
    @Override 
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromTouch) { 

    } 

    /** 
    * When user starts moving the progress handler 
    * */ 
    @Override 
    public void onStartTrackingTouch(SeekBar seekBar) { 
     // remove message Handler from updating progress bar 
     mHandler.removeCallbacks(mUpdateTimeTask); 
    } 

    /** 
    * When user stops moving the progress hanlder 
    * */ 
    @Override 
    public void onStopTrackingTouch(SeekBar seekBar) { 
     mHandler.removeCallbacks(mUpdateTimeTask); 
     int totalDuration = mp.getDuration(); 
     int currentPosition = utils.progressToTimer(seekBar.getProgress(), totalDuration); 

     // forward or backward to certain seconds 
     mp.seekTo(currentPosition); 

     // update timer progress again 
     updateProgressBar(); 
    } 

    /** 
    * On Song Playing completed 
    * if repeat is ON play same song again 
    * if shuffle is ON play random song 
    * */ 
    @Override 
    public void onCompletion(MediaPlayer arg0) { 

     // check for repeat is ON or OFF 
     if(isRepeat){ 
      // repeat is on play same song again 
      playSong(currentSongIndex); 
     } else if(isShuffle){ 
      // shuffle is on - play a random song 
      Random rand = new Random(); 
      currentSongIndex = rand.nextInt((songsList.size() - 1) - 0 + 1) + 0; 
      playSong(currentSongIndex); 
     } else{ 
      // no repeat or shuffle ON - play next song 
      if(currentSongIndex < (songsList.size() - 1)){ 
       playSong(currentSongIndex + 1); 
       currentSongIndex = currentSongIndex + 1; 
      }else{ 
       // play first song 
       playSong(0); 
       currentSongIndex = 0; 
      } 
     } 
    } 

    @Override 
    public void onDestroy(){ 
    super.onDestroy(); 
     mp.release(); 
    } 



} 

Answer 1

可以使用的getContext（）或getActivity（）/ getSherlockActivity（）来得到一个SherlockFragment里面的语境。

要开始，你需要调用活动：

Intent i = new Intent(getSherlockActivity(), PlayListActivity.class); 
startActivity(i);