Question

我正在使用listview作为列表项

的TextView
ImageView（显示附件图标）

我正在使用扩展ArrayAdapter并使用ViewHolder的自定义适配器，并且在自定义适配器中，如果存在附件，我会检查条件。如果为true，我会ImageView可见。一切正常，但滚动时ImageView消失了。

public class NoticeListAdapter  extends ArrayAdapter<String>{

    private final Activity context;
    private  List<String> img_url = new ArrayList<String>();
    private  List<String>  heading = new ArrayList<String>();
    private  List<Long>  createdDate = new ArrayList<Long>();
    private  List<String>  documentCategoryId = new ArrayList<String>();
    Date date = new Date();

    public NoticeListAdapter(Activity context, List<String> img_url, List<String> heading, List<Long> createdDate, List<String> documentCategoryId) {
        super(context, R.layout.attendance_list_item, heading);
        // TODO Auto-generated constructor stub
        this.context=context;
        this.img_url = img_url;
        this.heading = heading;
        this.createdDate = createdDate;
        this.documentCategoryId = documentCategoryId;
    }

    public static class ViewHolder {
        ImageView profilePicture;
        ImageView attachmentIcon;
        TextView txtemployeeName;
        TextView txtbulletinDate;
    }

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

        ViewHolder viewHolder;
        if(view == null){
            viewHolder = new ViewHolder();
            LayoutInflater inflater = LayoutInflater.from(getContext());
            view = inflater.inflate(R.layout.notice_list_item, parent, false);
            viewHolder.profilePicture = (ImageView) view.findViewById(R.id.profilePic);
            viewHolder.txtemployeeName = (TextView) view.findViewById(R.id.employeeName);
            viewHolder.txtbulletinDate = (TextView) view.findViewById(R.id.bulletinDate);
            viewHolder.attachmentIcon = (ImageView) view.findViewById(R.id.attachmentIcon);
            view.setTag(viewHolder);
        }else{
            viewHolder = (ViewHolder)view.getTag();
        }


        String description = heading.get(position);
        description = description.length()>40?description.substring(0,40)+"...":description;

        SharedPreferences pref = getContext().getSharedPreferences("authDetails", Context.MODE_PRIVATE);
        ImageLoader imageLoader = new ImageLoader(getContext());
        imageLoader.DisplayImage(pref.getString("base_url", "")+img_url.get(position), viewHolder.profilePicture);

        viewHolder.txtemployeeName.setText(description);
        viewHolder.txtbulletinDate.setText(DateUtils.getRelativeTimeSpanString(createdDate.get(position),  date.getTime(),  DateUtils.MINUTE_IN_MILLIS, DateUtils.FORMAT_ABBREV_RELATIVE));

        if(documentCategoryId.get(position).equalsIgnoreCase("0"))
            viewHolder.attachmentIcon.setVisibility(View.GONE);
        return view;
    }

}

Answer 1

只需更改您的密码：

if(documentCategoryId.get(position).equalsIgnoreCase("0"))
        viewHolder.attachmentIcon.setVisibility(View.GONE);

是：

if(documentCategoryId.get(position).equalsIgnoreCase("0"))
        viewHolder.attachmentIcon.setVisibility(View.GONE);
else
        viewHolder.attachmentIcon.setVisibility(View.VISIBLE);

Answer 2

此问题来自您的自定义ImageLoader实施。

粘贴你的代码，有一些错误没有显示图像。

或者，您可以从URL下载图片，并将其设置为profilePicture ImageView的来源，如下所示：

URL url = new URL(img_url.get(position));
Bitmap bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
viewHolder.profilePicture.setImageBitmap(bmp);

Answer 3

您的代码中存在ViewHolder实现问题。您不将持有者结果设置为非空视图。而且，不要检索最近创建的持有者。

尝试改变：

 view.setTag(viewHolder);
 }else{
 viewHolder = (ViewHolder)view.getTag();
 }

到这个

 view.setTag(viewHolder);
 }
 viewHolder = (ViewHolder)view.getTag();

和return view;之前：

view.setTag(viewHolder);

试试这个，固定代码：

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

    ViewHolder viewHolder;
    if(view == null){
        viewHolder = new ViewHolder();
        LayoutInflater inflater = LayoutInflater.from(getContext());
        view = inflater.inflate(R.layout.notice_list_item, parent, false);
        viewHolder.profilePicture = (ImageView) view.findViewById(R.id.profilePic);
        viewHolder.txtemployeeName = (TextView) view.findViewById(R.id.employeeName);
        viewHolder.txtbulletinDate = (TextView) view.findViewById(R.id.bulletinDate);
        viewHolder.attachmentIcon = (ImageView) view.findViewById(R.id.attachmentIcon);
        view.setTag(viewHolder);
    }
    viewHolder = (ViewHolder)view.getTag();

    String description = heading.get(position);
    description = description.length()>40?description.substring(0,40)+"...":description;

    SharedPreferences pref = getContext().getSharedPreferences("authDetails", Context.MODE_PRIVATE);
    ImageLoader imageLoader = new ImageLoader(getContext());
    imageLoader.DisplayImage(pref.getString("base_url", "")+img_url.get(position), viewHolder.profilePicture);

    viewHolder.txtemployeeName.setText(description);
    viewHolder.txtbulletinDate.setText(DateUtils.getRelativeTimeSpanString(createdDate.get(position),  date.getTime(),  DateUtils.MINUTE_IN_MILLIS, DateUtils.FORMAT_ABBREV_RELATIVE));

    if(documentCategoryId.get(position).equalsIgnoreCase("0"))
        viewHolder.attachmentIcon.setVisibility(View.GONE);
    view.setTag(viewHolder);
    return view;
}

如何在滚动时保持ListView项的状态？

3 个答案: