Question

由于某些原因，我的自定义适配器只允许我随时在列表视图中显示1个图像，我不知道为什么会发生这种情况。每个列表项中应该有一个图像，但只有最后一个列表项有图像集，所以我假设我重新使用了一个我不应该使用的值。其余的列表项目设置正确。

public class CustomAdapter extends ArrayAdapter<Item> {

    private ArrayList<Item> itemList;
    private ViewHolder holder; 
    private Context context;

    public CustomAdapter(Context context, int textViewResourceId, ArrayList<Item> list) {
        super(context, textViewResourceId, list);
        this.itemList = new ArrayList<Item>();
        this.itemList.addAll(list);
        this.context = context;
    }

    private class ViewHolder {
        ImageView img;
        TextView name;
        CheckBox access;
    }

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

        if (convertView == null) {
            LayoutInflater vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = vi.inflate(R.layout.list_grid, null);

            holder = new ViewHolder();
            holder.name = (TextView) convertView.findViewById(R.id.name);
            holder.access = (CheckBox) convertView.findViewById(R.id.checkBox1);
            holder.img = (ImageView) convertView.findViewById(R.id.imageView1);

            convertView.setTag(holder);
        } 

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

        Item it = itemList.get(position);

        new UrlLookup().execute(it.getUrl());
        holder.name.setText(it.getName());
        holder.access.setChecked(it.isSelected());

        return convertView;
    }

    //Create an image from the url passed in from the server and display it on the image view   
    private class UrlLookup extends AsyncTask<String, Integer, String>{
        Bitmap bmp;

        @Override
        protected String doInBackground(String... params){  
            try {
                URL u = new URL(params[0]);
                bmp = BitmapFactory.decodeStream(u.openConnection().getInputStream());
            } catch (Exception e) { e.printStackTrace(); }

            return "Done!";
        }

        @Override
        protected void onPostExecute(String result){
            super.onPostExecute(result);    
            holder.img.setImageBitmap(bmp);
        }
    }
}

Answer 1

您忘记了每次视图可见时您的持有人都会更改的事实。所以通常只有最后一个项目有图像。

AsyncTask的完成时间比getView方法要长很多。

您应该将ImageView传递给AsyncTask：

new UrlLookup().execute(it.getUrl(), holder.img);

调用AsyncTask

private class UrlLookup extends AsyncTask<Object, Integer, String>{
    Bitmap bmp;
    ImageView view;

    @Override
    protected String doInBackground(Object... params){ 
        view = (ImageView) params[1]; 
        try {
            URL u = new URL((String)params[0]);
            bmp = BitmapFactory.decodeStream(u.openConnection().getInputStream());
        } catch (Exception e) { e.printStackTrace(); }

        return "Done!";
    }

    @Override
    protected void onPostExecute(String result){
        super.onPostExecute(result);    
        view.setImageBitmap(bmp);
    }
}

现在，您将在每个AsyncTask中获得每行ImageView的引用。

我想向你们指出，Koush有一个出色的项目来做你想要的事情： UrlImageViewHelper

ListView的自定义适配器（仅显示1个ImageView）

1 个答案: