将项目加载到微调器时，空指针异常

2 回答

• 0

  首先创建助手实例 .
  帮助器在 helper.getCategories(); 处于null是问题所在 .

  回复于 2024-04-20T12:18:01+08:00
• 0

  您必须实现Array适配器（扩展到ArrayAdapter） . 并覆盖getDropDownView .

  这是为了样品 .

  public class CategorySpinnerAdapter extends ArrayAdapter<Category> {
  
      List<Category> list = new ArrayList<>();
  
      private Context context;
  
      public CategorySpinnerAdapter(Context context, int resource, Category[] categories) {
          super(context, resource, categories);
  
          this.context = context;
      }
  
      @Override
      public View getDropDownView(int position, View convertView, ViewGroup parent) {
          return getMyView(position, convertView, parent);
      }
  
      @Override
      public View getView(int position, View convertView, ViewGroup parent) {
  
          return getMyView(position, convertView, parent);
      }
  
  
      private View getMyView(int position, View convertView, ViewGroup parent){
          CSViewHolder viewHolder;
          if(convertView == null){
              convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.category_spinner_row, parent, false);
              viewHolder = new CSViewHolder(convertView);
              convertView.setTag(viewHolder);
          }else{
              viewHolder = (CSViewHolder)convertView.getTag();
          }
  
          viewHolder.fill(list.get(position));
  
          return convertView;
      }
  
      /**
       * Load channel list
       * @param cursor
       */
      public void setList(Cursor cursor){
          list.clear();
          Log.i(getClass().getName(), String.valueOf(cursor));
          for(cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
  
              // The Cursor is now set to the right position
              Category category = new Category();
  
              category.setTitle(CursorUtil.getStringColumnFromCursor(cursor, GoftagramContract.CategoryEntry.COLUMN_TITLE));
              category.setId(CursorUtil.getStringColumnFromCursor(cursor, GoftagramContract.CategoryEntry.COLUMN_SERVER_ID));
              list.add(category);
          }
      }
  
  
  
  
      @Override
      public int getCount() {
          return list.size();
      }
  
      @Override
      public Category getItem(int position) {
          return list.get(position);
      }
  
      class CSViewHolder{
          private TextView titleView;
          private ImageView thumbnailView;
  
          public CSViewHolder(View itemView){
  
              titleView = (TextView)itemView.findViewById(R.id.category_spinner_row_title);
              thumbnailView = (ImageView)itemView.findViewById(R.id.category_spinner_row_image);
  
          }
  
          public void fill(Category category){
              titleView.setText(category.getTitle());
  
              if(!TextUtils.isEmpty(category.getThumbnail())){
                  Glide.with(context)
                          .load(category.getThumbnail())
                          .into(thumbnailView);
              }else{
                  thumbnailView.setImageResource(R.drawable.ic_discuss);
              }
  
          }
      }
  }
  

  用于使用适配器

  categorySpinnerAdapter = new CategorySpinnerAdapter(this, R.layout.category_spinner_row, new Category[]{});
  

  回复于 2024-04-20T12:18:01+08:00