安卓layout margin 代码变更

ViewGroup.MarginLayoutParams layoutParams=(ViewGroup.MarginLayoutParams)surfacev.getLayoutParams();
layoutParams.width=tw;
layoutParams.height=th;
layoutParams.leftMargin=left;
layoutParams.topMargin=top;

handler.post(new Runnable() {
   @Override
   public void run() {
       surfacev.setLayoutParams(layoutParams);
       surfacev.requestLayout();  //这个找了半天才知道。原来这个要写！！！
   }
});