Android imageadapter可以设置为空？

Question

我有一个来自asynchtask的代码：

Configuration configuration = getResources().getConfiguration();
int screenWidthDp = configuration.screenWidthDp;
GridView grid_foto=new GridView(context);
grid_foto.setNumColumns(3);
LinearLayout.LayoutParams parametri = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT);
grid_foto.setLayoutParams(parametri);
grid_foto.setAdapter(new ImageAdapter(context, album_foto, screenWidthDp));
grid_foto.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
        anteprima.setVisibility(View.VISIBLE);
        findViewById(R.id.loading_2).setVisibility(View.VISIBLE);
        new DownloadImageTask(anteprima_img).execute(id_foto[position]);
    }
});
grid_linear.addView(grid_foto);

此代码在活动开始时调用，并在用户添加图像时调用。问题是imageadapter不断增长，而不是仅在传递图像时才满。 例如：活动开始时适配器中有image_1，image_2，image_3：当用户添加照片时...而不是image_1，image_2，image_3，image_4适配器是image_1，image_2，image_3，image_1，image_2 ，image_3，image_4 !!!!

为什么这个东西？我怎么强行清理适配器？

ImageAdapter：

public class ImageAdapter extends BaseAdapter implements ListAdapter {
    private Context context;
    int width=0;
    public ImageAdapter(Context context, String[] album_foto,int larghezza) {
        super();
        this.context = context;
        width=larghezza;
        GridViewConfig.addImageUrls(album_foto);
    }
    @Override
    public int getCount() {
        return GridViewConfig.getResim_list().size();
    }
    @Override
    public Object getItem(int position) {
        return GridViewConfig.getResim_list().get(position);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if(convertView==null){
            imageView=new ImageView(context);
            imageView.setLayoutParams(new GridView.LayoutParams(width/3,width/3));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(2,2,2,2);
        }else{
            imageView=(ImageView)convertView;
        }
        new DownloadImageTask(imageView).execute(GridViewConfig.getResim_list().get(position));
        return imageView;
    }
    private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
        ImageView bmImage;
        public DownloadImageTask(ImageView bmImage) {
            this.bmImage = bmImage;
        }
        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }
        protected void onPostExecute(Bitmap result) {
            bmImage.setImageBitmap(result);
        }
    }
}