radioButtons = new RadioButton[rgMain.getChildCount()];  //遍历RadioGroup
for (int i = 0; i < radioButtons.length; i++) {
    radioButtons[i] = (RadioButton) rgMain.getChildAt(i);
    radioButtons[i].setTag(i);　　　　　　　　　　　　　　　　//设置tag
    radioButtons[i].setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            if (b)
                //切换ViewPager页面
                showFragment((int) compoundButton.getTag());　　　　//获取tag
        }
    });
}