当在列表中向上滚动时，ArrayAdapter抛出异常

Question

我使用一个自定义适配器来创建一个列表，通常它工作得很好，但是每当我向下滚动一点并向上滚动时，一旦标题应该显示/加载(我猜是后者)，它就会崩溃。它按预期工作，我可以在列表中滚动，只要我喜欢，但是一旦我回到列表的顶部，就会抛出一个IllegalStateException。LogCat输出如下行:

ERROR/ArrayAdapter(287):你必须为TextView提供一个资源ID

我使用的列表适配器的代码:

public class SeparatedListAdapter extends BaseAdapter implements ObservableAdapter{
    public final Map<String, Adapter> sections = new LinkedHashMap<String, Adapter>();
    public final ArrayAdapter<String> headers;
    public final static int TYPE_SECTION_HEADER = 0;
    public SeparatedListAdapter(Context context, int resId) {
        super();
        headers = new ArrayAdapter<String>(context, resId);
    }
    public void addSection(String section, Adapter adapter) {
        this.headers.add(section);
        this.sections.put(section, adapter);
        adapter.registerDataSetObserver(mDataSetObserver);
    }
    public void removeObserver() {
        for (Map.Entry<String, Adapter> it : sections.entrySet()) {
            if (it.getValue() instanceof ObservableAdapter) {
                ObservableAdapter adapter = (ObservableAdapter)it.getValue();
                adapter.removeObserver();
            }
        }
    }
    public void clear() {
        headers.clear();
        sections.clear();
        notifyDataSetInvalidated();
    }
    @Override
    public Object getItem(int position) {
        for (Object section : this.sections.keySet()) {
            Adapter adapter = sections.get(section);
            int size = adapter.getCount() + 1;
            if (position == 0) return section;
            if (position < size) return adapter.getItem(position - 1);
            position -= size;
        }
        return null;
    }
    @Override
    public int getCount() {
        int total = 0;
        for (Adapter adapter : this.sections.values())
            total += adapter.getCount() + 1;
        return total;
    }
    @Override
    public int getViewTypeCount() {
        int total = 1;
        for (Adapter adapter : this.sections.values())
            total += adapter.getViewTypeCount();
        return total;
    }
    @Override
    public int getItemViewType(int position) {
        int type = 1;
        for (Object section : this.sections.keySet()) {
            Adapter adapter = sections.get(section);
            int size = adapter.getCount() + 1;
            if (position == 0) return TYPE_SECTION_HEADER;
            if (position < size) return type + adapter.getItemViewType(position - 1);
            position -= size;
            type += adapter.getViewTypeCount();
        }
        return -1;
    }

    @Override
    public boolean areAllItemsEnabled() {
        return false;
    }
    @Override
    public boolean isEnabled(int position) {
        return (getItemViewType(position) != TYPE_SECTION_HEADER);
    }
    @Override
    public boolean isEmpty() {
        return getCount() == 0;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        int sectionnum = 0;
        for (Object section : this.sections.keySet()) {
            Adapter adapter = sections.get(section);
            int size = adapter.getCount() + 1;
            if (position == 0) return headers.getView(sectionnum, convertView, parent);
            if (position < size) return adapter.getView(position - 1, convertView, parent);
            position -= size;
            sectionnum++;
        }
        return null;
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public boolean hasStableIds() {
        return false;
    }    
    private DataSetObserver mDataSetObserver = new DataSetObserver() {
        @Override
        public void onChanged() {
            notifyDataSetChanged();   
        }
    };
}

我很迷茫，如果有人有什么建议，我将不胜感激。

Answer 1

使用以下类型的代码

if (position == 0) return ...;
if (position < size) return ...;
position -= size;

当size>= 2时，存在position变为负而不被设置为0的危险。