android TranslateAnimation动画焦点跟随问题

给一个activity设置移动动画，移动后，焦点并没有跟随，实现焦点跟随的效果，可以这样设置：

 mainlayout = (RelativeLayout) findViewById(R.id.main_activity);
 final Animation animation = new TranslateAnimation(0, -100, 0, 0);
  animation.setDuration(50);

  animation.setAnimationListener(new AnimationListener() {

   @Override
   public void onAnimationStart(Animation animation) {
    // TODO Auto-generated method stub

   }

   @Override
   public void onAnimationRepeat(Animation animation) {
    // TODO Auto-generated method stub

   }
   // 这里就是实现焦点跟随
   @Override
   public void onAnimationEnd(Animation animation) {
    mainlayout.clearAnimation();
    FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(getWh().x, getWh().y);
    lp.setMargins(-100, 0, getWh().x + 100, getWh().y);//getwh()自定义的一个获取宽和高的方法
    mainlayout.setLayoutParams(lp);
   }