ListActivity 中的 BaseAdapter 未显示正确的项目

Question

我有一个 ListActivity，其中我试图在列表下显示一个 ImageView。我尝试通过创建自己的 BaseAdapter 并在 getView 方法中使用两种不同的方法来实现此目的，一种用于 List，一种用于 ImageView.我设法让 ImageView 按我想要的方式显示在列表下，但我遇到的问题是列表显示不正确。

由于某种原因，列表中的任何项目在用户向下滚动之前不会出现在屏幕上，都会填充错误的数据，如下所示：

----Top Screen------
|     Item 1       |
|     Item 2       |
|     Item 3       |
|     Item 4       |
----Bottom Screen---
|     Item 1       |   <--Items not on the screen show
|     Item 1       |   <--as item 1 once the user scrolls
|     Image View   |   

它应该是这样的：

----Top Screen------
|     Item 1       |
|     Item 2       |
|     Item 3       |
|     Item 4       |
----Bottom Screen---
|     Item 5       |
|     Item 6       |
|     Image View   |

我的自定义 BaseAdapter

    private class MyCustomAdapter extends BaseAdapter {
        private static final int TYPE_ITEM = 0;
        private static final int TYPE_SEPARATOR = 1;
        private static final int TYPE_MAX_COUNT = TYPE_SEPARATOR + 1;

        private ArrayList<HashMap<String,String>> mData = new ArrayList<HashMap<String,String>>();
        private LayoutInflater mInflater;    
        private TreeSet mSeparatorsSet = new TreeSet();

        public MyCustomAdapter() {
            mInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        public void addItem(final String header, final String message) {
            HashMap<String,String> item = new HashMap<String,String>();
            item.put(LINE_1, header);
            item.put(LINE_2, message);

            mData.add(item);
            notifyDataSetChanged();
        }

        public void addImageItem() {
            HashMap<String,String> item = new HashMap<String,String>();
            item.put(LINE_1, "");
            item.put(LINE_2, "");

            mData.add(item);
            mSeparatorsSet.add(mData.size() - 1);
            notifyDataSetChanged();
        }

        @Override
        public int getItemViewType(int position) {
            return mSeparatorsSet.contains(position) ? TYPE_SEPARATOR : TYPE_ITEM;
        }

        @Override
        public int getViewTypeCount() {
            return TYPE_MAX_COUNT;
        }

        public int getCount() {
            return mData.size();
        }

        public Object getItem(int position) {
            return mData.get(position);
        }

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

        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder vh = null;
            int type = getItemViewType(position);
            System.out.println("getView " + position + " " + convertView + " type = " + type);
            if (convertView == null) {
                vh = new ViewHolder();
                switch (type) {
                    case TYPE_ITEM:
                        convertView = mInflater.inflate(R.layout.instructions_two_row, null);
                        vh.header = (TextView) convertView.findViewById(R.id.instructions_header);
                        vh.message = (TextView) convertView.findViewById(R.id.instructions_message);
                        vh.header.setText((CharSequence) mData.get(position).get(LINE_1));
                        vh.message.setText((CharSequence) mData.get(position).get(LINE_2));
                        break;
                    case TYPE_SEPARATOR:
                        convertView = mInflater.inflate(R.layout.instructions_image, null);
                        vh.imageView = (ImageView) convertView.findViewById(R.id.instuct_image);
                        vh.imageView.setImageDrawable(getResources().getDrawable(R.drawable.instructions));
                        break;
                }
                convertView.setTag(vh);
            }
            else {
                vh = (ViewHolder) convertView.getTag();
            }           
            return convertView;
        }   
    }

    public static class ViewHolder {
        public TextView header;
        public TextView message;
        public ImageView imageView;
    }

感谢您的帮助帮助大家！

Answer 1

getView 在滚动时回收视图。如果convertView不为null，您仍然需要检查它的类型是否正确并为其设置正确的值。