试图在列表视图中着色一行的背景

我正在用listview中的歌词制作媒体播放应用程序，列表视图随着媒体进展而滚动，现在我希望当前播放的经文在不同颜色的列表视图中突出显示。所以我在处理程序中使用下面的代码，但是我得到了一个NPE。试图在列表视图中着色一行的背景

if(mediaPlayer.getCurrentPosition()/1000 > 0 && mediaPlayer.getCurrentPosition()/1000 < 20){ 
          listView.smoothScrollToPosition(3); 
          View element = listView.getChildAt(3); 
          element.setBackgroundColor(0xff0000ff);

完整代码

public class MainActivity extends Activity { 

    TextView T,S1; 
    MediaPlayer mediaPlayer; 
    ScrollView sv; 
    SeekBar seek_bar; 
    boolean lang = true; 
    Typeface tf; 
    String [] LyricsE; 
    String [] LyricsH; 
    ListView listView; 
    Button b; 
    private ArrayAdapter dataAdapter; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     //mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.stair); 
     //mediaPlayer.start(); 
     LyricsE = new String [] {"","","",getResources().getString(R.string.V1E),getResources().getString(R.string.V2E), 
       getResources().getString(R.string.V3E), 
       getResources().getString(R.string.V4E),getResources().getString(R.string.V4E),getResources().getString(R.string.V5E), 
       getResources().getString(R.string.V6E),getResources().getString(R.string.V7E),getResources().getString(R.string.V8E), 
       getResources().getString(R.string.V9E),getResources().getString(R.string.V10E),getResources().getString(R.string.V11E), 
       getResources().getString(R.string.V12E),getResources().getString(R.string.V13E),getResources().getString(R.string.V14E), 
       getResources().getString(R.string.V15E),getResources().getString(R.string.V16E),getResources().getString(R.string.V17E), 
       getResources().getString(R.string.V18E),getResources().getString(R.string.V19E),getResources().getString(R.string.V20E), 
       getResources().getString(R.string.V21E),getResources().getString(R.string.V22E),getResources().getString(R.string.V23E), 
       getResources().getString(R.string.V24E),getResources().getString(R.string.V25E),getResources().getString(R.string.V26E), 
       getResources().getString(R.string.V27E),getResources().getString(R.string.V28E),getResources().getString(R.string.V29E), 
       getResources().getString(R.string.V30E),getResources().getString(R.string.V31E),getResources().getString(R.string.V32E), 
       getResources().getString(R.string.V33E),getResources().getString(R.string.V34E),getResources().getString(R.string.V35E), 
       getResources().getString(R.string.V36E),getResources().getString(R.string.V37E),getResources().getString(R.string.V38E), 
       getResources().getString(R.string.V39E),getResources().getString(R.string.V40E),getResources().getString(R.string.V41E), 
       getResources().getString(R.string.V42E)}; 

     LyricsH = new String[] {"","","",getResources().getString(R.string.V1H),getResources().getString(R.string.V2H), 
       getResources().getString(R.string.V3H), 
       getResources().getString(R.string.V4H),getResources().getString(R.string.V4H),getResources().getString(R.string.V5H), 
       getResources().getString(R.string.V6H),getResources().getString(R.string.V7H),getResources().getString(R.string.V8H), 
       getResources().getString(R.string.V9H),getResources().getString(R.string.V10H),getResources().getString(R.string.V11H), 
       getResources().getString(R.string.V12H),getResources().getString(R.string.V13H),getResources().getString(R.string.V14H), 
       getResources().getString(R.string.V15H),getResources().getString(R.string.V16H),getResources().getString(R.string.V17H), 
       getResources().getString(R.string.V18H),getResources().getString(R.string.V19H),getResources().getString(R.string.V20H), 
       getResources().getString(R.string.V21H),getResources().getString(R.string.V22H),getResources().getString(R.string.V23H), 
       getResources().getString(R.string.V24H),getResources().getString(R.string.V25H),getResources().getString(R.string.V26H), 
       getResources().getString(R.string.V27H),getResources().getString(R.string.V28H),getResources().getString(R.string.V29H), 
       getResources().getString(R.string.V30H),getResources().getString(R.string.V31H),getResources().getString(R.string.V32H), 
       getResources().getString(R.string.V33H),getResources().getString(R.string.V34H),getResources().getString(R.string.V35H), 
       getResources().getString(R.string.V36H),getResources().getString(R.string.V37H),getResources().getString(R.string.V38H), 
       getResources().getString(R.string.V39H),getResources().getString(R.string.V40H),getResources().getString(R.string.V41H), 
       getResources().getString(R.string.V42H)}; 



     String fontPath = "fonts/DroidSansDevanagari-Regular.ttf"; 
     tf = Typeface.createFromAsset(getAssets(), fontPath); 

     mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.stair); 
     b = (Button)findViewById(R.id.button1); 
     Button L = (Button)findViewById(R.id.button2); 
     L.setOnClickListener(Lang); 
     b.setOnClickListener(on); 
     T = (TextView)findViewById(R.id.textView1); 
     S1 = (TextView)findViewById(R.id.textView2); 
     seek_bar =(SeekBar)findViewById(R.id.seekBar1); 
     listView = (ListView) findViewById(R.id.listView1); 
     if(lang){ 
      //ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.list,R.id.textView2, LyricsE); 
      //listView.setAdapter(adapter); 
      dataAdapter = new arrayAdapter(MainActivity.this, LyricsE); 

      listView.setAdapter(dataAdapter); 
     } 
     if(!lang){ 
      //ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.list,R.id.textView2, LyricsH); 
      //listView.setAdapter(adapter); 

      dataAdapter = new arrayAdapter(MainActivity.this, LyricsH); 

      listView.setAdapter(dataAdapter); 

     } 

    } 

    private View.OnClickListener on = new View.OnClickListener() { 

     @Override 
     public void onClick(View v) { 
      boolean flag = true; 
      int B = 0; 
      // mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.stair); 

      if(mediaPlayer.isPlaying()){ 

       mediaPlayer.pause(); 
       B = mediaPlayer.getCurrentPosition(); 
       flag = false; 
       b.setText("Play"); 
       System.out.println("in is.playing"); 
      }else if(!flag && !mediaPlayer.isPlaying()){ 
       mediaPlayer.seekTo(B); 
       b.setText("Pause"); 
       System.out.println("in flag and !playing"); 
      } 




      else{ 
       b.setText("Pause"); 
       System.out.println("Normal execution"); 

       //listView = (ListView) findViewById(R.id.listView1); 
       // mediaPlayer = MediaPlayer.create(MainActivity.this, R.raw.stair); 
       mediaPlayer.start(); 
       seek_bar.setMax(mediaPlayer.getDuration()); 


       seek_bar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() { 

        @Override 
        public void onStopTrackingTouch(SeekBar seekBar) { 

        } 

        @Override 
        public void onStartTrackingTouch(SeekBar seekBar) { 

        } 

        @Override 
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {     
         if(mediaPlayer != null && fromUser){ 

          mediaPlayer.seekTo(progress); 
         } 
        } 

       }); 




       final Handler handler = new Handler(); 
       handler.post(new Runnable(){ 

        @Override 
        public void run(){ 
         int X = mediaPlayer.getCurrentPosition(); 
         S1.setText(""+X); 
         setProgressText(); 
         seek_bar.setProgress(mediaPlayer.getCurrentPosition()); 
          if(mediaPlayer.getCurrentPosition()/1000 > 0 && mediaPlayer.getCurrentPosition()/1000 < 20){ 
          //listView.smoothScrollToPosition(3); 
          //View element = listView.getChildAt(3); 
          //element.setBackgroundColor(Color.YELLOW); 
          System.out.println("FIrst if"); 


           int wantedPosition = 3; 
           int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount(); // This is the same as child #0 
           int wantedChild = wantedPosition - firstPosition; 
           // Say, first visible position is 8, you want position 10, wantedChild will now be 2 
           // So that means your view is child #2 in the ViewGroup: 
           if (wantedChild < 0 || wantedChild >= listView.getChildCount()) { 
           System.out.println("Unable to get view for desired position, because it's not being displayed on screen."); 
            return; 
           } 
           listView.smoothScrollToPosition(wantedChild); 
           View wantedView = listView.getChildAt(wantedChild); 
           wantedView.setBackgroundColor(Color.YELLOW); 





         }else if(mediaPlayer.getCurrentPosition()/1000 > 20 && mediaPlayer.getCurrentPosition()/1000 < 54){ 
         // listView.smoothScrollToPosition(4); 
         // View element = listView.getChildAt(4); 
         // element.setBackgroundColor(Color.YELLOW); 
          System.out.println("2 if"); 


          int wantedPosition = 4; 
          int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount(); // This is the same as child #0 
          int wantedChild = wantedPosition - firstPosition; 
          // Say, first visible position is 8, you want position 10, wantedChild will now be 2 
          // So that means your view is child #2 in the ViewGroup: 
          if (wantedChild < 0 || wantedChild >= listView.getChildCount()) { 
          System.out.println("Unable to get view for desired position, because it's not being displayed on screen."); 
           return; 
          } 
          listView.smoothScrollToPosition(wantedChild); 
          View wantedView = listView.getChildAt(wantedChild); 
          wantedView.setBackgroundColor(Color.YELLOW); 








         }else if(mediaPlayer.getCurrentPosition()/1000 > 54 && mediaPlayer.getCurrentPosition()/1000 < 67){ 
          //listView.smoothScrollToPosition(5); 
          //View element = listView.getChildAt(5); 
          //element.setBackgroundColor(Color.YELLOW); 
          System.out.println("3 if"); 


          int wantedPosition = 5; 
          int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount(); // This is the same as child #0 
          int wantedChild = wantedPosition - firstPosition; 
          // Say, first visible position is 8, you want position 10, wantedChild will now be 2 
          // So that means your view is child #2 in the ViewGroup: 
          if (wantedChild < 0 || wantedChild >= listView.getChildCount()) { 
          System.out.println("Unable to get view for desired position, because it's not being displayed on screen."); 
           return; 
          } 
          listView.smoothScrollToPosition(wantedChild); 
          View wantedView = listView.getChildAt(wantedChild); 
          wantedView.setBackgroundColor(Color.YELLOW); 






         }else if(mediaPlayer.getCurrentPosition()/1000 > 67 && mediaPlayer.getCurrentPosition()/1000 < 75){ 
          listView.smoothScrollToPosition(6); 
          System.out.println("4 if"); 
         }else if(mediaPlayer.getCurrentPosition()/1000 > 20 && mediaPlayer.getCurrentPosition()/1000 < 54){ 
          listView.smoothScrollToPosition(7); 
          System.out.println("5 if"); 
         }else if(mediaPlayer.getCurrentPosition()/1000 > 20 && mediaPlayer.getCurrentPosition()/1000 < 54){ 
          listView.smoothScrollToPosition(8); 
          System.out.println("6 if"); 
         }else if(mediaPlayer.getCurrentPosition()/1000 > 20 && mediaPlayer.getCurrentPosition()/1000 < 54){ 
          listView.smoothScrollToPosition(9); 
          System.out.println("7 if"); 
         }else if(mediaPlayer.getCurrentPosition()/1000 > 20 && mediaPlayer.getCurrentPosition()/1000 < 54){ 

         } 


         handler.postDelayed(this, 1000L); 

        } 
       }); 
      } 
     } 
    }; 


    protected void setProgressText() { 
     String X ; 
     final int HOUR = 60*60*1000; 
     final int MINUTE = 60*1000; 
     final int SECOND = 1000; 

     int durationInMillis = mediaPlayer.getDuration(); 
     int curVolume = mediaPlayer.getCurrentPosition(); 

     int durationHour = durationInMillis/HOUR; 
     int durationMint = (durationInMillis%HOUR)/MINUTE; 
     int durationSec = (durationInMillis%MINUTE)/SECOND; 

     int currentHour = curVolume/HOUR; 
     int currentMint = (curVolume%HOUR)/MINUTE; 
     int currentSec = (curVolume%MINUTE)/SECOND; 

     if(durationHour>0){ 
      X = (""+String.format("%02d:%02d:%02d/%02d:%02d:%02d", 
        currentHour,currentMint,currentSec, durationHour,durationMint,durationSec));    
     }else{ 
      X = (""+String.format("%02d:%02d/%02d:%02d", 
        currentMint,currentSec, durationMint,durationSec)); 
     } 


     // Toast.makeText(getApplicationContext(), ""+X, 10000); 
     T = (TextView)findViewById(R.id.textView1); 
     T.setText(""+X); 
    } 

    private View.OnClickListener Lang = new View.OnClickListener() { 

     @Override 
     public void onClick(View v) { 
      ListView listView = (ListView) findViewById(R.id.listView1); 
      String [] Change; 
      int index = listView.getFirstVisiblePosition(); 
      View v1 = listView.getChildAt(0); 
      int top = (v1 == null) ? 0 : v1.getTop(); 

      if(lang){ 

       Change = LyricsH; 
       lang = false; 
      } 
      else{ 
       Change = LyricsE; 



       lang = true; 
      } 
      /* ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, R.layout.list,R.id.textView2, Change); 
      listView.setAdapter(adapter); 
      listView.setSelectionFromTop(index, top); */ 

      dataAdapter = new arrayAdapter(MainActivity.this, Change); 

      listView.setAdapter(dataAdapter); 
      listView.setSelectionFromTop(index, top); 


     } 
    }; 


    public boolean fontMag(){ 
     return lang; 
    } 







    public class arrayAdapter extends ArrayAdapter<String[]> { 
     private final Context context; 
     private final String[] lyrics; 
     public arrayAdapter(Context context, String[]lyrics) { 
      super(context, R.layout.list); 
      this.context = context; 
      this.lyrics = lyrics; 

     } 
     public int getCount() { 
      return lyrics.length; 

     } 

     public String[] getItem(int position) { 

      return (lyrics); 
     } 


     public long getItemId(int arg0) { 

      return arg0; 
     } 

     @Override 
     public View getView(int position, View convertView, ViewGroup parent) { 
      LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 



      if (convertView == null) { 
       convertView = inflater.inflate(R.layout.list, parent, false); 
      } 
      TextView textView = ((TextView) convertView.findViewById(R.id.textView2)); 
      textView.setText(lyrics[position]); 






      return convertView; 
     } 
    } 

}

任何指针，我可能会去错了吗？

来源

2013-09-21 Heretic Monk

空指针，因为你的看法是不正确的异常膨胀，必须引起..请张贴logcat的细节...

另外一个更好的方式来实现你想要将做到这一点

int wantedPosition = 10; // Whatever position you're looking for 
    int firstPosition = listView.getFirstVisiblePosition() - listView.getHeaderViewsCount(); // This is the same as child #0 
    int wantedChild = wantedPosition - firstPosition; 
    // Say, first visible position is 8, you want position 10, wantedChild will now be 2 
    // So that means your view is child #2 in the ViewGroup: 
    if (wantedChild < 0 || wantedChild >= listView.getChildCount()) { 
     Log.w(TAG, "Unable to get view for desired position, because it's not being displayed on screen."); 
     return; 
    } 
    // Could also check if wantedPosition is between listView.getFirstVisiblePosition() and listView.getLastVisiblePosition() instead. 
    View wantedView = listView.getChildAt(wantedChild);

什么看到这个link

来源

2013-09-21 10:38:50

谢谢，我正在尝试这个。 –

你可以详细解释wantedPosition吗？是我想要滚动到的位置吗？ –

Yes..wantedPostion： - 你想设置颜色的位置..试一试.. :) –

试图在列表视图中着色一行的背景

回答

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