Question

我通过Picasso Library在我的自定义适配器中加载图像，然后在我的ListFragment中显示它。当我尝试滚动时，一些图像会改变顺序（我认为重复使用单元格有问题）。

异步下载图片的最佳位置是什么？我在带有viewholder的自定义适配器中执行此操作。

public class PostsAdapter extends BaseAdapter {
private static final String TAG = "tag.example.tag";
private static final String URL_PREFIX = "http://someapi.com/v1/api/";
private Context mContext;
private ArrayList<Post> mData;
private static LayoutInflater inflater = null;

public PostsAdapter(Context context, ArrayList<Post> data) {
  mContext = context;
  mData = data;
  inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE)
}

@Override
public boolean isEnabled(int position) {
  return true;
}

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

@Override
public Object getItem(int i) {
  return i;
}

@Override
public long getItemId(int i) {
  return i;
}

@Override
public View getView(int i, View view, ViewGroup viewGroup) {
  View v = view;
  ViewHolder holder = null;
  if(view == null)
    v = inflater.inflate(R.layout.post_listviewrow, null);

  holder = new ViewHolder();

  holder.imageView = (ImageView) v.findViewById(R.id.imageView);

  Post post = (Post) mData.get(i);
  // Download image with Picasso
  holder.imageView.setTag(post.getPictureUrl());
  Picasso.with(mContext).load(URL_PREFIX + post.getPictureUrl()).into(holder.imageView);
  return v;
}

  static class ViewHolder {
    TextView titleTextView;
    ImageView imageView;
  }
}

Answer 1

解：将getView方法更改为此类

@Override
public View getView(int i, View view, ViewGroup viewGroup) {

    final ViewHolder holder;

    if(view == null) {
        view = inflater.inflate(R.layout.post_listviewrow, null);
        holder = new ViewHolder();
        holder.imageView = (ImageView) view.findViewById(R.id.imageView);
        holder.titleTextView = (TextView) view.findViewById(R.id.textview);
        holder.progressBar = (ProgressBar) view.findViewById(R.id.progressBar);


        view.setTag(holder);
    } else {
        holder = (ViewHolder) view.getTag();
    }
        // Get position
        Post post = (Post) mData.get(i);

        holder.titleTextView.setText(post.getTitle());
        Picasso picasso = Picasso.with(mContext);
        picasso.setIndicatorsEnabled(true);
        holder.progressBar.setVisibility(View.VISIBLE);
        picasso.load(URL_PREFIX + post.getPictureUrl())
                .placeholder(R.drawable.placeholder)
                .fit()
                .centerCrop()
                .into(holder.imageView, new Callback() {
                    @Override
                    public void onSuccess() {
                        holder.progressBar.setVisibility(View.GONE);
                    }
                    @Override
                    public void onError() {}
        });

    return view;
}
static class ViewHolder {

    TextView titleTextView;
    ImageView imageView;
    ProgressBar progressBar;

}

无论如何，您认为适配器是放置下载任务的正确位置吗？

listview更改顺序

1 个答案: