android 通过字符串来获取R下面资源的ID 值

try{
            Field field=R.drawable.class.getField("icon");
            int i= field.getInt(new R.drawable());
            Log.d("icon", i + "");
        }catch(Exception e){
            Log.e("icon",e.toString());
        }

Resources res=getResources();
        int i=res.getIdentifier("icon","drawable",getPackageName());