Android 碎片中使用碎片，用handler更新UI时报错?报错

class myrunn implements Runnable {
@Override
public void run() {
list = new ArrayList<String>();
for (int i = 0; i < 40; i++) {
list.add("新闻" + i);
}
handler2.obtainMessage(0x8).sendToTarget();


}
}


Handler handler2 = new Handler() {
public void handleMessage(android.os.Message msg) {
if (msg.what == 0x8) {
adapter = new HorizListViewAdapter(list, getActivity());
browser_horiz_list.setAdapter(adapter);
}


};
};

报错：Can't create handler inside thread that has not called Looper.prepare()