Android Listview 从 url 加载 imageview

Question

我正在从 url 加载图像并将其输入到我的 ListView 中。问题是每次我滚动 ListView 时 ImageView 都会更改它的图像。

我使用的代码来自:How to load an ImageView by URL in Android?从 url 加载图像:

public class ImageLoadTask extends AsyncTask<Void, Void, Bitmap> {

    private String url;
    private ImageView imageView;

    public ImageLoadTask(String url, ImageView imageView) {
        this.url = url;
        this.imageView = imageView;
    }

    @Override
    protected Bitmap doInBackground(Void... params) {
        try {
            URL urlConnection = new URL(url);
            HttpURLConnection connection = (HttpURLConnection) urlConnection
                    .openConnection();
            connection.setDoInput(true);
            connection.connect();
            InputStream input = connection.getInputStream();
            Bitmap myBitmap = BitmapFactory.decodeStream(input);
            return myBitmap;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Bitmap result) {
        super.onPostExecute(result);
        imageView.setImageBitmap(result);
    }

}

在我的 ListAdapter 中，我使用此代码加载图像:

public View getView(int position, View convertView, ViewGroup parent){
    ViewHolderItem holder = new ViewHolderItem();
    if (convertView == null) {
     LayoutInflater inflater = (LayoutInflater) main.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.cell, null);

        holder.name = (TextView) convertView.findViewById(R.id.name);
        holder.thumb = (ImageView) convertView.findViewById(R.id.thumb);
        holder.duration = (TextView) convertView.findViewById(R.id.duration);
        //holder.code = (TextView) convertView.findViewById(R.id.code);
        convertView.setTag(holder);
    }
    else{
         holder = (ViewHolderItem) convertView.getTag();
    }


    holder.name.setText(this.main.countries.get(position).title);
    if (holder.thumb != null) {
        new DownloadImageTask(holder.thumb).execute(this.main.countries.get(position).thumb);
    }
    return convertView;
}

在我的主要 Activity 中:

   public void get_data(String data){
        try {
            JSONArray data_array=new JSONArray(data);
            for (int i = 0 ; i < data_array.length() ; i++){
                JSONObject obj=new JSONObject(data_array.get(i).toString());

                Countries add=new Countries();
                add.title = obj.getString("title");
                add.thumb = obj.getString("artwork_url");

                countries.add(add);
            }

            adapter.notifyDataSetChanged();

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

Answer 1

尝试使用Picasso library .使用起来非常简单，例如。

Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);

毕加索有自动内存和磁盘缓存。这在 ListView 中非常重要。

Where can I get the variable name context?

获取上下文:

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    Context context = parent.getContext();
    [...]
}