Question

我有一个ListView，每个项目都有一张图片。我从服务器下载图像。由于有两个以上的图像，加载变得非常慢，当您向下滚动时，您会看到上面的图像，并且必须等待很长时间才能更改为正确的图像。我已经尝试使用此帖子中的提示：http://lucasr.org/2012/04/05/performance-tips-for-androids-listview/ 但它仍然很慢。什么是改善这一点的最好和最简单的方法。以下是我BaseAdapter班级的代码：

public class GetAllEntrysListViewAdapter extends BaseAdapter {

private JSONArray dataArray;
private Activity activity;
private static LayoutInflater inflater = null;
public Cursor cursor;
private SQLiteDatabase dbase;
DbHelper dbh;
private Context context;
String pos;
Integer markerID;
public String objectID;



private static final String baseUrlForImage = "http://...";

public GetAllEntrysListViewAdapter(JSONArray jsonArray, Context context, Integer markerID) {
    this.dataArray = jsonArray;
    this.context= context;
    this.markerID = markerID;
    inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

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

    final ListCell cell;
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.get_all_entry_list_view_cell, null);

        cell = new ListCell();

        cell.likes = (TextView) convertView.findViewById(R.id.listViewLikes);
        cell.note = (TextView) convertView.findViewById(R.id.listViewNote);
        cell.img = (ImageView) convertView.findViewById(R.id.listViewImg);
        cell.likeImage = (ImageView) convertView.findViewById(R.id.heartImage);

        convertView.setTag(cell);

    }
    else {
        cell = (ListCell)convertView.getTag();
    }

    cell.position = position;

    try {
        JSONObject jsonObject = this.dataArray.getJSONObject(position);
        cell.likes.setText(jsonObject.getString("likes"));
        cell.note.setText(jsonObject.getString("note"));
        cell.entryID = jsonObject.getString("id");
        String img = jsonObject.getString("image");
        String urlForImageInServer = baseUrlForImage + img;

        new AsyncTask<String, Void, Bitmap>() {
            private int mPosition = position;
            private ListCell mCell = cell;
            @Override
            protected Bitmap doInBackground(String... params) {
                //download image
                String url = params[0];
                Bitmap icon = null;

                try {
                    InputStream in = new java.net.URL(url).openStream();
                    icon = BitmapFactory.decodeStream(in);
                } catch(MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

                return icon;
            }

            @Override
            protected void onPostExecute(Bitmap result) {
                if (cell.position == mPosition) {
                    cell.img.setImageBitmap(result);
                }
            }

        }.execute(urlForImageInServer);


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

}

public static class ListCell {
    private TextView likes;
    private TextView note;
    private ImageView img;
    public ImageView likeImage;
    public int position;
    public String entryID;
}

}

Answer 1

不要重新发明轮子。不要为AsyncTask的每个项目创建ListView。使用一些库，它将下载，缓存并帮助显示您的图像，如Picasso：

Picasso.with(context).load("file:///android_asset/DvpvklR.png").into(imageView2);

对于JSONObject的每个项目，将ListView拆分为单独的参数是多余的。创建POJO个对象的数组，但不只是JSONObject的数组。或者，如果您的ListView仅显示图片，则可以将String数组传递给适配器。

PS并尝试查找和阅读新文章。你提到了2012年的文章。

Answer 2

到目前为止，最受欢迎的SO帖子是@ Lazy load of images in ListView。它提到了毕加索以及其他包装。玩得开心......

Answer 3

你可以使用Volley Library它会让你放松并做一切

http://www.androidhive.info/2014/07/android-custom-listview-with-image-and-text-using-volley/

var users = Users.Instance;
users.addNewUser(1, "Vera");
users.countUsers();

Android ListView缓慢加载图片

3 个答案: