空指针异常的原因

1，在hashmap中取不存在的键所对应的值

        TextView textTitle = (TextView)findViewById(R.id.post_name);

        textTitle.setText("公告");

        TextView postDetails = (TextView)findViewById(R.id.post_details);

        postDetails.setText(hashMap.get("newslist_title").toString());

        TextView postTime = (TextView)findViewById(R.id.post_time);

        postTime.setText(hashMap.get("newslist_time").toString());

        //postInflate = getLayoutInflater();