How to change FastScrollerThumbDrawable of a ListView on Android 2.3

My goal is to replace the listview's default fastScrollThumbDrawable to a custom Drawable. I found this link and the style for Activity takes effect on Android4.0 and later versions.

But on Android2.3 the xml style method is unavailable. I tried the reflection method from this link .But this still unavailable.From the android source code 2.3.6 I find "mThumbDrawalbe" member variable exactly exists in FastScroller.java. And mFastScroller exists in Abslistview.java. So the "mThumberDrawable" really exists. But FastScroller is a package private class .Can't java reflection access package private class's member variable?

There are some references: Custom Listview Fast Scrollbar in android

AbsListView.java src: http://ift.tt/1yCWOhe

FastScroller.java src: http://ift.tt/1DzCnRw

Here's my method under android 2.3.

    private void setFastScrollerThumb(ListView view){
    if (android.os.Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
        try {
            java.lang.reflect.Field f = AbsListView.class.getDeclaredField("mFastScroller");
            f.setAccessible(true);
            Object fastScrollerObj= f.get(view);
            Class <?>  fastScrollerCls=f.getType();
            Field [] allFileds=fastScrollerCls.getDeclaredFields();

            for(Field item:allFileds){
                Log.i("ZYStudio", "item is:"+item.getName()+"|"+item.getType().getName());
            }
            //'allFields' result empty
            f=fastScrollerCls.getDeclaredField("mThumbDrawable");
            f.setAccessible(true);
            Drawable drawable = (Drawable) f.get(fastScrollerObj);
            drawable = getResources().getDrawable(R.drawable.novel_catagory_fastscroll_thumb);
            f.set(fastScrollerObj, drawable);
        } catch (Exception e) {
            e.printStackTrace();
            Log.i("ZYStudio", "fastscrollerThumb occured:"+e.getClass().getName());
        }
    }
}