关于viewholder总是报Java.lang.NullPointerException。

很奇怪的问题，先保存下来在，找时间来想想问什么！viewholder总是报Java.lang.NullPointerException，如果在后面的if else选择加上判断holder！＝null的话就会导致list view缓存问题，会出现重复出现之前的item的问题。

<span style="font-weight: normal;">public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
holder = new ViewHolder();
convertView = inflater.inflate(R.layout.item_rank, null);
</span><pre name="code" class="java" style="font-size: 14px; font-weight: bold;"><span style="font-weight: normal;"><span style="white-space:pre">	</span>holder.rankingNo = (TextView) convertView.findViewById(R.id.rankingNo);
holder.photoLogo = (CircleImageView) convertView.findViewById(R.id.photoLogo);
holder.effortNo = (TextView) convertView.findViewById(R.id.effortNo);
holder.rankName = (TextView) convertView.findViewById(R.id.rankName);</span>

} else { holder = (ViewHolder) convertView.getTag(); } if (type.equals("popularity") && listPopularity != null &&holder!=null) { RankPopularityResult.Result.Member member = listPopularity.get(position); if (member.mbrType == 0) { ImageLoader.getInstance().displayImage(getImageUrl(member.photoId),
holder.photoLogo, options); } else if (member.mbrType == 1) { ImageLoader.getInstance().displayImage(member.wcPhotoPath, holder.photoLogo, options); } NumberFormat currencyFormat = NumberFormat.getCurrencyInstance(); //int转化为钱的类型 holder.rankingNo.setText(String.valueOf(member.ranking));
holder.rankName.setText(member.nickName); holder.effortNo.setText(currencyFormat.format(member.effort)); Log.i("member.nickName", String.valueOf(member.nickName)); } else if (type.equals("company") && listCompany != null&&
holder!=null) { Log.i("listCompany", String.valueOf(listCompany)); RankCompanyResult.Result.Member member = listCompany.get(position); ImageLoader.getInstance().displayImage(getImageUrl(member.sequareLogoPhoto),
holder.photoLogo, options); // Log.i("", String.valueOf()); NumberFormat currencyFormat = NumberFormat.getCurrencyInstance(); holder.rankingNo.setText(String.valueOf(member.ranking)); holder.rankName.setText(member.companyName); Log.i("member.companyName",
String.valueOf(member.companyName)); holder.effortNo.setText(currencyFormat.format(member.effort)); } // Log.i("", String.valueOf());//Java.lang.NullPointerException return convertView; } private class ViewHolder { private TextView rankingNo; private TextView
rankName; private TextView effortNo; private CircleImageView photoLogo; }

这是参考google出来的修改后的代码！

<pre name="code" class="java">public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
holder = new ViewHolder();
convertView = inflater.inflate(R.layout.item_rank, null);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}

holder.rankingNo = (TextView) convertView.findViewById(R.id.rankingNo);
holder.photoLogo = (CircleImageView) convertView.findViewById(R.id.photoLogo);
holder.effortNo = (TextView) convertView.findViewById(R.id.effortNo);
holder.rankName = (TextView) convertView.findViewById(R.id.rankName);
if (type.equals("popularity") && listPopularity != null ) {

RankPopularityResult.Result.Member member = listPopularity.get(position);

if (member.mbrType == 0) {
ImageLoader.getInstance().displayImage(getImageUrl(member.photoId), holder.photoLogo, options);
} else if (member.mbrType == 1) {
ImageLoader.getInstance().displayImage(member.wcPhotoPath, holder.photoLogo, options);
}
NumberFormat currencyFormat = NumberFormat.getCurrencyInstance();
holder.rankingNo.setText(String.valueOf(member.ranking));
holder.rankName.setText(member.nickName);
holder.effortNo.setText(currencyFormat.format(member.effort));
Log.i("member.nickName", String.valueOf(member.nickName));

} else if (type.equals("company") && listCompany != null ) {
Log.i("listCompany", String.valueOf(listCompany));
RankCompanyResult.Result.Member member = listCompany.get(position);
ImageLoader.getInstance().displayImage(getImageUrl(member.sequareLogoPhoto), holder.photoLogo, options);
// Log.i("", String.valueOf());
NumberFormat currencyFormat = NumberFormat.getCurrencyInstance();
holder.rankingNo.setText(String.valueOf(member.ranking));
holder.rankName.setText(member.companyName);
Log.i("member.companyName", String.valueOf(member.companyName));
holder.effortNo.setText(currencyFormat.format(member.effort));
}
// Log.i("", String.valueOf());
//Java.lang.NullPointerException
return convertView;
}

private class ViewHolder {
private TextView rankingNo;
private TextView rankName;
private TextView effortNo;
private CircleImageView photoLogo;

}