android - 具有不同项目布局的 ListView 的 ViewHolders

Question

我的 ListView 有两种不同类型的布局:一种有图像，另一种没有图像。我尝试做类似 this 的事情.我覆盖了 BaseAdapter 的 getView:

public View getView(int position, View convertView, ViewGroup parent) {
        Map<String, String> item = mData.get(position);
        if(item.get("image_location").equals("") == true){
            ViewHolderWithoutImage holder = new ViewHolderWithoutImage();
            if(convertView == null){
                convertView = mInflater.inflate(R.layout.row_without_image, null);
                holder.title = (TextView)convertView.findViewById(R.id.title);
                holder.firstParagraph = (TextView)convertView.findViewById(R.id.first_paragraph);
                convertView.setTag(holder);
            }else{
                holder = (ViewHolderWithoutImage)convertView.getTag();
            }
            holder.title.setText(mData.get(position).get("title").toString());
            holder.firstParagraph.setText(item.get("first_paragraph").toString());

        }else{
            ViewHolderWithImage holder = new ViewHolderWithImage();
            Bitmap bm = null;
            if(convertView == null){
                convertView = mInflater.inflate(R.layout.row_with_image, null);
                holder.title = (TextView)convertView.findViewById(R.id.title_image);
                holder.firstParagraph = (TextView)convertView.findViewById(R.id.first_paragraph_image);
                holder.image = (ImageView)convertView.findViewById(R.id.image);
                convertView.setTag(holder);
            }else{
                holder = (ViewHolderWithImage)convertView.getTag();
            }

            holder.title.setText(mData.get(position).get("title").toString());
            holder.firstParagraph.setText(item.get("first_paragraph").toString());
            String location = imageBaseUrl + item.get("image_location");
            bm = downloadImage(location);
            holder.image.setImageBitmap(bm);
        }
        return convertView;
    }

我的 ViewHolders 类:

static class ViewHolderWithImage {
        TextView title;
        TextView firstParagraph;
        ImageView image;
    }

    static class ViewHolderWithoutImage {
        TextView title;
        TextView firstParagraph;
    }

它在没有第二部分的情况下也能工作，但是当它进入时会崩溃

holder = (ViewHolderWithImage)convertView.getTag();

部分当 item.get("image_location").equals("") != true 出现 java.lang.reflect.InvocationTargetException 时。有什么办法可以解决这个问题吗？

Answer 1

我认为这是因为 convertView 的标签持有不同类型的 ViewHolder。尝试检查 convertView 类型:

if(item.get("image_location").equals("") == true){
    ...
    if(convertView == null || !(convertView.getTag() instanceof ViewHolderWithoutImage)){
    ...
}else{
    ...
    if(convertView == null || !(convertView.getTag() instanceof ViewHolderWithImage)){
        convertView = mInflater.inflate(R.layout.row_with_image, null);
        ...

附言最好使用系统方法来处理不同的布局(覆盖 getItemViewType())。 There is good article on this topic .