/**
  * 设置radiobutton图片大小
  */
private void setRadioButtonDrawable() {
  RadioButton[] rbs = new RadioButton[3];
  rbs[0] = btnHome;
  rbs[1] = btnReport;
  rbs[2] = btnMy;
  for (RadioButton rb : rbs) {
    //挨着给每个RadioButton加入drawable限制边距以控制显示大小
    Drawable[] drawables = rb.getCompoundDrawables();
    //获取drawables
    Rect r = new Rect(0, 0, drawables[1].getMinimumWidth() * 2 / 3, drawables[1].getMinimumHeight() * 2 / 3);
    //定义一个Rect边界
    drawables[1].setBounds(r);
    //添加限制给控件
    rb.setCompoundDrawables(null, drawables[1], null, null);
  }
}