自定义 Adapter 的 getView() 中的空指针异常

Posted 2023-04-13

【中文标题】自定义 Adapter 的 getView() 中的空指针异常

【英文标题】：Null pointer exception in getView() of custom Adapter

【发布时间】：2012-08-01 06:58:06

【问题描述】：

我正在为我的 ListView 使用这个自定义适配器：

public class SideMenuAdapter extends BaseAdapter 

    private static final int TYPE_MAX_COUNT = 2;
    private static LayoutInflater inflater = null;
    private Activity activity;
    public static String[] values;
    ListView myList;

    public SideMenuAdapter(Activity a, String[] sa, ListView lv) 

        values = sa;
        activity = a;
        inflater = (LayoutInflater) activity
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        myList = lv;
    

    public int getCount() 

        return values.length;
    

    public Object getItem(int position) 

        return position;
    

    public long getItemId(int position) 

        return position;
    

    public static class ViewHolder 

        public TextView mainText;
        public TextView sideText;
    

    public View getView(int position, View convertView, ViewGroup parent) 

        ViewHolder holder = new ViewHolder();
        View vi = convertView;
        if (vi == null) 

            //here i am getting NullPointerException
            vi.setTag(holder);
         else 

            holder = (ViewHolder) vi.getTag();
        
        vi = inflater.inflate(R.layout.side_menu_list_item, null);
        holder.mainText = (TextView) vi.findViewById(R.id.mainText_sideMenu);
        holder.sideText = (TextView) vi.findViewById(R.id.sideText_sideMenu);
        holder.mainText.setText(values[position]);
        if(position == 2)

            holder.sideText.setText("3");
            holder.sideText.setBackgroundResource(R.drawable.orange);
        
        return convertView;
    
    @Override
    public int getViewTypeCount() 

        return TYPE_MAX_COUNT;
    

我正在以这种方式将适配器设置为我的列表视图：

    String menuItems[] = new String[]  "My Wants", "Profile", "Notifications",
            "Feedback", "Logout" ;
    listView1.setAdapter(new SideMenuAdapter(this, menuItems, listView1));

我哪里错了？？

【参考方案1】：

你应该在你的vi.setTag(holder);之前初始化vi

【讨论】：

到我用于 ListView 项目的布局？？

是的。这是使用自定义 BaseAdapter thinkandroid.wordpress.com/2010/01/13/custom-baseadapters

的示例

【参考方案2】：

试试这个，可能对你有帮助...

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

    ViewHolder holder = new ViewHolder();
    View vi = convertView;
    if (vi == null) 
        LayoutInflater inflater = ((Activity)activity).getLayoutInflater();
        vi = inflater.inflate(R.layout.side_menu_list_item, null);
        holder.mainText = (TextView) vi.findViewById(R.id.mainText_sideMenu);
        holder.sideText = (TextView) vi.findViewById(R.id.sideText_sideMenu);
        vi.setTag(holder);
     else 

        holder = (ViewHolder) vi.getTag();
    

    holder.mainText.setText(values[position]);
    if(position == 2)

        holder.sideText.setText("3");
        holder.sideText.setBackgroundResource(R.drawable.orange);
    
    return convertView;

【讨论】：

耶... :) 这对我有帮助：***.com/questions/12590342/…