原因出在adapter的getView方法中

原先的寫法：

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		View view = null;
		ViewHolder holder = null;
		if(convertView == null) {
			holder = new ViewHolder();
			LayoutInflater inflater = getLayoutInflater();
			view = inflater.inflate(R.layout.list_cell, null);
			holder.tvTitle = (TextView) view.findViewById(R.id.tv_title);
			holder.tvDetail = (TextView) view.findViewById(R.id.tv_content);
			holder.tvComment = (TextView) view.findViewById(R.id.tv_comment);
		} else {
			view = convertView;
		}
		
		holder.tvTitle.setText(newsList.get(position).getTitle());
		holder.tvDetail.setText(newsList.get(position).getDetail());
		holder.tvComment.setText(newsList.get(position).getComment() + "跟帖");
			
		return view;
		}
 

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			ViewHolder holder = null;
			if(convertView == null) {
				holder = new ViewHolder();
				LayoutInflater inflater = getLayoutInflater();
				convertView = inflater.inflate(R.layout.list_cell, null);
				holder.tvTitle = (TextView) convertView.findViewById(R.id.tv_title);
				holder.tvDetail = (TextView) convertView.findViewById(R.id.tv_content);
				holder.tvComment = (TextView) convertView.findViewById(R.id.tv_comment);
				convertView.setTag(holder);
			} else {
				holder = (ViewHolder) convertView.getTag();
			}
			
			holder.tvTitle.setText(newsList.get(position).getTitle());
			holder.tvDetail.setText(newsList.get(position).getDetail());
			holder.tvComment.setText(newsList.get(position).getComment() + "跟帖");
			
			return convertView;
		}