Question

我在logcat中有错误

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference

尝试查看列表中的图片为此代码创建一个类我认为方法中的错误查看getView但我不知道它究竟在哪里我认为可能在这里的thumbNail定义

public class useradaptor extends BaseAdapter {


             private Activity activity;
             private LayoutInflater inflater;
             private List<user> userItems;

ImageLoader imageLoader = AppController.getInstance().getImageLoader();

public useradaptor(Activity activity, List<user> userItems) {
    this.activity = activity;
    this.userItems = userItems;
}

@Override
public int getCount() {
    return userItems.size();
}

@Override
public Object getItem(int location) {
    return userItems.get(location);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    user u = userItems.get(position);
    if (imageLoader == null)
        imageLoader = AppController.getInstance().getImageLoader();
    NetworkImageView thumbNail = (NetworkImageView) convertView.findViewById(R.id.imageview);
    thumbNail.setImageUrl(u.getPicture(), imageLoader);

    Cache cache = AppController.getInstance().getRequestQueue().getCache();
    Cache.Entry entry = cache.get(u.getPicture());
    if(entry != null){
        try {
            String data = new String(entry.data, "UTF-8");
            // handle data, like converting it to xml, json, bitmap etc.,
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
    }else{
        // cached response doesn't exists. Make a network call here
    }
    return convertView;
  }
}

Answer 1

如果convertView没有为您提供回收的行，则

null将为ListView。当convertView为null时，您需要通过某种方式创建列表行。通常情况下，您使用LayoutInflater，最好是通过getLayoutInflater()上的Activity调用{。}}。

尝试在空对象引用上调用虚方法'android.view.View android.view.View.findViewById（int）'

1 个答案: