Question

我正在尝试创建这样的自定义列表视图：http://i.stack.imgur.com/l8ZOc.png

目前我设法创建了它，但是存在问题。例如，当有8个项目时，它会加载前4个项目，然后在向下滚动时加载重新加载的项目。向下滚动时，它工作正常。

然而，当从底部向上滚动时，在列表的中间，它立即移动到顶部，跳过2-3-4。项目。然后你可以再次正常向下滚动，但是当向上滚动时，它会立即进入列表的顶部。

我如何防止这种情况发生？

这是我的代码：

public class MyActivity extends Activity implements AdapterView.OnItemClickListener {

    String headers[];
    String image_urls[];

    List<MyMenuItem> menuItems;
    ListView mylistview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);

        menuItems = new ArrayList<MyMenuItem>();
        headers = getResources().getStringArray(R.array.header_names);
        image_urls = getResources().getStringArray(R.array.image_urls);


        for (int i = 0; i < headers.length; i++) {
            MyMenuItem item = new MyMenuItem(headers[i], image_urls[i]);
            menuItems.add(item);
        }

        mylistview = (ListView) findViewById(R.id.list);
        MenuAdapter adapter = new MenuAdapter(this, menuItems);
        mylistview.setAdapter(adapter);
        mylistview.setOnItemClickListener(this);
    }
}

public class MyMenuItem {

    private String item_header;
    private String item_image_url;

    public MyMenuItem(String item_header, String item_image_url){
        this.item_header=item_header;
        this.item_image_url=item_image_url;
    }

    public String getItem_header(){
        return item_header;
    }

    public void setItem_header(String item_header){
        this.item_header=item_header;
    }

    public String getItem_image_url(){
        return item_image_url;
    }

    public void setItem_image_url(String item_image_url){
        this.item_image_url=item_image_url;
    }


}

public class MenuAdapter extends BaseAdapter{

    Context context;
    List<MyMenuItem> menuItems;

    MenuAdapter(Context context, List<MyMenuItem> menuItems) {
        this.context = context;
        this.menuItems = menuItems;
    }

    @Override
    public int getCount() {
        return menuItems.size();
    }

    @Override
    public Object getItem(int position) {
        return menuItems.get(position);
    }

    @Override
    public long getItemId(int position) {
        return menuItems.indexOf(getItem(position));
    }

    private class ViewHolder {
        ImageView ivMenu;
        TextView tvMenuHeader;
    }



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

        ViewHolder holder = null;

        LayoutInflater mInflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.menu_item, null);
            holder = new ViewHolder();

            holder.tvMenuHeader = (TextView) convertView.findViewById(R.id.tvMenuHeader);
            holder.ivMenu = (ImageView) convertView.findViewById(R.id.ivMenuItem);

            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        MyMenuItem row_pos = menuItems.get(position);

        Picasso.with(context)
                .load(row_pos.getItem_image_url())
             //   .placeholder(R.drawable.empty)
             //   .error(R.drawable.error)
                .into(holder.ivMenu);

        holder.tvMenuHeader.setText(row_pos.getItem_header());

        Log.e("Test", "headers:" + row_pos.getItem_header());
        return convertView;
    }

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    tools:context=".MyActivity">


        <ListView
            android:id="@+id/list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            />



</RelativeLayout>

Answer 1

使用延迟加载机制加载图像数据。有一个很好的例子here

向上滚动时，我的自定义列表视图会立即滚动回第一个元素。如何防止这种情况并使滚动顺利进行

1 个答案: