特殊的listview适配器，滚动时类更改的图像

Question

我的应用程序是红色的，但只有listview有一个小问题，我向下滚动图像更改，是不对的。我认为问题在于功能。首先我设置一个标志，然后我加载数据。

my adapter:

public class BinderData_bioscoop extends BaseAdapter {
LayoutInflater inflater;
List<HashMap<String,String>> BioscopenLijst;
ViewHolder holder;
public BinderData_bioscoop() {}

public BinderData_bioscoop(Activity act, List<HashMap<String,String>> map) {
    this.BioscopenLijst = map;
    inflater = (LayoutInflater) act.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

public int getCount() {
    return BioscopenLijst.size();
}

public Object getItem(int arg0) {
    return null;
}

public long getItemId(int position) {
    return 0;
}

public View getView(int position, View convertView, ViewGroup parent) {
    View vi=convertView;
    if(convertView==null){
        vi = inflater.inflate(R.layout.list_row_bioscoop, null);
        holder = new ViewHolder();
        holder.naam = (TextView)vi.findViewById(R.id.naam); // naam
        holder.poster =(ImageView)vi.findViewById(R.id.poster); // logo
        vi.setTag(holder);
    } else{
        holder = (ViewHolder)vi.getTag();
    }

    // Invoegen van variabels
    holder.naam.setText(BioscopenLijst.get(position).get("naam")); // naam
    holder.poster.setTag(BioscopenLijst.get(position).get("logo")); //logo
    new GetPoster().execute(holder.poster);
    return vi;
}

static class ViewHolder{
    TextView naam;
    ImageView poster;
}
}

班级“getposter”

public class GetPoster extends AsyncTask<ImageView, Void, Bitmap> {
ImageView imageView = null; //imagevieuw waar de foto moet komen
Bitmap return_var_DIB;

@Override
protected Bitmap doInBackground(ImageView... imageViews) { //doen in de achtergrond
    this.imageView = imageViews[0];
    BitmapFactory.Options options;

    String poster_key = imageViews[0].getTag().toString();
    if(poster_key.equals("")) {
        /*=== niet's doen vanwege geen key ===*/
        return_var_DIB = null;
    } else {
        /* === uitvoeren van code wanneer er een key is ===*/
        poster_key = poster_key + ".jpg"; //exstentie aan de key toevoegen
        //app map zoeken
        File sdCard = Environment.getExternalStorageDirectory(); // Ophalen van de SD kaart locatie
        /*
        File android_directory = new File(sdCard.getAbsolutePath() + "/android"); //Aanmaken van de map
        android_directory.mkdirs(); // map aanmaken
        File android_data_directory = new File(sdCard.getAbsolutePath() + "/android/data"); //Aanmaken van de map
        android_data_directory.mkdirs(); // map aanmaken
        File mc_directory = new File(sdCard.getAbsolutePath() + "/android/data/be.me.app"); //Aanmaken van de map
        mc_directory.mkdirs(); // map aanmaken
        */
        File directory = new File(sdCard.getAbsolutePath() + "/android/data/be.app.me/case"); //Aanmaken van de map
        directory.mkdirs(); // map aanmaken
        String poster_pad = sdCard + "/android/data/be.me.app/case/" + poster_key;
        File poster = new File(directory, poster_key); // aanmaken
        if (poster.exists()) {
            //output poster
            return_var_DIB = BitmapFactory.decodeFile(poster_pad); //file to bitmap
        } else {
            //Downloaden
            return_var_DIB = download_Image((String) poster_key, (File) poster, (String) poster_pad);
        }

    }
    return return_var_DIB;
}

@Override
protected void onPostExecute(Bitmap result) { //als alles klaar is
    if(result != null) {
        imageView.setImageBitmap(result);
        imageView.setTag("");
    }
}
private Bitmap download_Image(String key, File poster, String poster_pad) { //foto downloaden
    Bitmap poster_bmp = null;
    //
    try {
        URL url = new URL("http://www.app.de/data/foto_adapter.php?key=" + key);
        URLConnection connection = url.openConnection();
        connection.connect();

        InputStream input = new BufferedInputStream(url.openStream()); // het bestand downloaden
        OutputStream output = new FileOutputStream(poster); // opslaan van het bestand
        OutputStreamWriter osw = new OutputStreamWriter(output); //van het bestand

        byte data[] = new byte[1024];
        //total = 0;
        int count;
        while ((count = input.read(data)) != -1) {
            //total += count;
            // Publish the progress
            //publishProgress((int) (total * 100 / fileLength)); // updaten progress bar
            output.write(data, 0, count);
        }
        poster_bmp = BitmapFactory.decodeFile(poster_pad);

        osw.flush(); // legen van de output
        osw.close(); // sluiten an de output
        input.close(); // (lege) input sluiten
    } catch (Exception e) {
        // Error Log
        Log.e("Error", e.getMessage());
        e.printStackTrace();
    }
    //
    return poster_bmp;
}
}