android ViewHolder 空指针异常

来源：互联网发布：windows音频设备隔离编辑：程序博客网时间：2024/05/03 13:47

android ViewHolder 空指针异常的时候，需要检测一下几个地方
1.首先确认是否是显示空指针的地方少加了一个convertView引用导致了空指针异常。

1）出错前代码：

public View getView(int position, View convertView, ViewGroup parent) {
      ViewHolder holder = null;
       if(holder == null) {
             holder = new ViewHolder();
             if(convertView == null) {
                    convertView = mInflater.inflate(R.layout.inbox_listitem, null);
                   System.out.println("convertView----------------->"+convertView);
            }

holder.image = (ImageView)findViewById(R.id.connecter_image);

holder.nametxt = (TextView)findViewById(R.id.connecter_name);

            holder.messagetxt = (TextView)findViewById(R.id.connect_message);
            System.out.println("holder.image----->"+holder.image);//此处出现空指针
           System.out.println("holder.nametxt ---->"+holder.nametxt);//此处出现空指针
            System.out.println("holder.messagetxt ---->"+holder.messagetxt);//此处出现空指针
            convertView.setTag(holder);

     }else {
            holder = (ViewHolder) convertView.getTag();
     }

     System.out.println("position------------------->" +position);
     System.out.println("mSmsPic.get(position)------------->" +mSmsPic.get(position));
     System.out.println("mContactsName.get(position)------------->" +mContactsName.get(position));
     System.out.println("mContactsmessage.get(position)------------->" +mContactsmessage.get(position));

     holder.image.setImageBitmap(mSmsPic.get(position));
     holder.nametxt.setText(mContactsName.get(position));
     holder.messagetxt.setText(mContactsmessage.get(position));
     return convertView;
}

少添加了一个convertView。

2）更改后代码：
public View getView(int position, View convertView, ViewGroup parent) {
      ViewHolder holder = null;
      if(holder == null) {
           holder = new ViewHolder();
           if(convertView == null) {
                 convertView = mInflater.inflate(R.layout.inbox_listitem, null);
                 System.out.println("convertView----------------->"+convertView);
           }

           holder.image= (ImageView)convertView.findViewById(R.id.connecter_image);
           holder.nametxt =(TextView）convertView.findViewById(R.id.connecter_name);
           holder.messagetxt = (TextView) convertView.findViewById(R.id.connect_message);

          System.out.println("holder.image----->"+holder.image);
          System.out.println("holder.nametxt ---->"+holder.nametxt);
          System.out.println("holder.messagetxt ---->"+holder.messagetxt);
          convertView.setTag(holder);
    }else {
        holder = (ViewHolder) convertView.getTag();
   }

   System.out.println("position------------------->" +position);
   System.out.println("mSmsPic.get(position)------------->" +mSmsPic.get(position));
   System.out.println("mContactsName.get(position)------------->" +mContactsName.get(position));
   System.out.println("mContactsmessage.get(position)------------->" +mContactsmessage.get(position));

    holder.image.setImageBitmap(mSmsPic.get(position));
    holder.nametxt.setText(mContactsName.get(position));
    holder.messagetxt.setText(mContactsmessage.get(position));
    return convertView;
}

2. 检测layout.inbox_listitem.xml 引用的组件ID名称是否和声明的一致，确保R.id.connecter_name在xml文件中一定存在。
convertView.findViewById(R.id.connecter_name); 是否应用到别的xml文件，导致允许的时候边缘通过，实际调用的时候出现空指针异常。

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