通过java反射改变listview fastscroll图片

try {
Field f = AbsListView.class.getDeclaredField("mFastScroller");
f.setAccessible(true);
Object o=f.get(getListView());
f=f.getType().getDeclaredField("mThumbDrawable");
f.setAccessible(true);
Drawable drawable=(Drawable) f.get(o);
drawable=getResources().getDrawable(R.drawable.icon);
f.set(o,drawable);
Toast.makeText(this, f.getType().getName(), 1000).show();
} catch (Exception e) {
throw new RuntimeException(e);
}