android 2.1에서의 getRotation() API 함수 에러...

[android 2.1]
WindowManager wm=(WindowManager)getSystemService(Context.WINDOW_SERVICE);
  Display display =wm.getDefaultDisplay();
  
  android.view.ViewGroup.LayoutParams lp = backButton.getLayoutParams();
  
  if(display.getWidth() > display.getHeight()){
   lp.width = 199;
   backButton.setLayoutParams(lp);
   
  }else{
   lp.width = 120;
   backButton.setLayoutParams(lp);
  }