application not working on android 4.0.4

i was working on a media player app on 2.2 that worked fine on my phone nexus S on 2.3.6 i upgraded my phone to ice cream sandwich 4.0.4 it's not working anymore when i commented this portion of code it worked what's the problem with this code :

public void loadfiles()
     {
     File file = new File("/sdcard");
     String [] liste;
     liste=file.list();
     String txt=new String("");
     db.begin_transaction();
     for(int i=0;i<liste.length;i++){
     File file1 =new File("/sdcard/"+liste[i]);
     if (file1.isDirectory()&&(i!=liste.length-2)){search("/sdcard/"+liste[i]);}}
     db.end_transaction();
     }
 public void search(String url)
 {
     File file = new File(url);
     String [] liste;
     liste=file.list();
     String txt = new String("");
     for(int i=0;i<liste.length;i++)
     {
         File file1 =new File(url+"/"+liste[i]);
         if (file1.isDirectory()){search(url+"/"+liste[i]);}
         else if(liste[i].endsWith(".mp3"))
         {
         //HashMap<String, String> info = MP3HeaderInfo.getInfo(file.getAbsolutePath()+"/"+liste[i]);
 
         //db.insererUneChanson((liste[i]).substring(0,liste[i].length()-4),file.getAbsolutePath()+"/"+liste[i],info.get("Artist"),info.get("Album"),info.get("Year"));
 
         }
     }
 

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