在列表视图中从SQL Server获取图像

Question

我正在尝试在SQL Server数据库中获取图像和文本，并在列表视图或网格视图中显示它们。但是，我只得到文本，没有显示图像。程序确实找到了路径，但是无法显示图像。影像的存储方式类似于/foldername/a.png。我尝试过

Picasso.with(context).load("/foldername/"parkingList.get(position).getImg()).into(viewHolder.imageView); 

但不起作用。如何获取图像？

public class MainActivity extends AppCompatActivity {

private ArrayList<ClassListItems> itemArrayList;  //List items Array
private MyAppAdapter myAppAdapter; //Array Adapter
private GridView gridView; // GridView
private boolean success = false; // boolean
private ConnectionClass connectionClass; //Connection Class Variable
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    gridView = (GridView) findViewById(R.id.gridView); //GridView Declaration
    connectionClass = new ConnectionClass(); // Connection Class Initialization
    itemArrayList = new ArrayList<ClassListItems>(); // Arraylist Initialization

    // Calling Async Task
    SyncData orderData = new SyncData();
    orderData.execute("");
}

// Async Task has three overrided methods,
private class SyncData extends AsyncTask<String, String, String>
{
    String msg = "Internet/DB_Credentials/Windows_FireWall_TurnOn Error, See Android Monitor in the bottom For details!";
    ProgressDialog progress;

    @Override
    protected void onPreExecute() //Starts the progress dailog
    {
        progress = ProgressDialog.show(MainActivity.this, "Synchronising",
                "GridView Loading! Please Wait...", true);
    }

    @Override
    protected String doInBackground(String... strings)  // Connect to the database, write query and add items to array list
    {
        try
        {
            Connection conn = connectionClass.CONN(); //Connection Object
            if (conn == null)
            {
                success = false;
            }
            else {
                // Change below query according to your own database.
                String query = "SELECT name,photo FROM MainTable";
                Statement stmt = conn.createStatement();
                ResultSet rs = stmt.executeQuery(query);
                if (rs != null) // if resultset not null, I add items to itemArraylist using class created
                {
                    while (rs.next())
                    {
                        try {
                            itemArrayList.add(new ClassListItems(rs.getString("name"),rs.getString("photo")));
                        } catch (Exception ex) {
                            ex.printStackTrace();
                        }
                    }
                    msg = "Found";
                    success = true;
                } else {
                    msg = "No Data found!";
                    success = false;
                }
            }
        } catch (Exception e)
        {
            e.printStackTrace();
            Writer writer = new StringWriter();
            e.printStackTrace(new PrintWriter(writer));
            msg = writer.toString();
            success = false;
        }
        return msg;
    }

    @Override
    protected void onPostExecute(String msg) // disimissing progress dialoge, showing error and setting up my GridView
    {
        progress.dismiss();
        Toast.makeText(MainActivity.this, msg + "", Toast.LENGTH_LONG).show();
        if (success == false)
        {
        }
        else {
            try {
                myAppAdapter = new MyAppAdapter(itemArrayList, MainActivity.this);
                gridView.setChoiceMode(GridView.CHOICE_MODE_MULTIPLE);
                gridView.setAdapter(myAppAdapter);
            } catch (Exception ex)
            {

            }

        }
    }
}

public class MyAppAdapter extends BaseAdapter         //has a class viewholder which holds
{
    public class ViewHolder
    {
        TextView textName;
        ImageView imageView;
    }

    public List<ClassListItems> parkingList;

    public Context context;
    ArrayList<ClassListItems> arraylist;

    private MyAppAdapter(List<ClassListItems> apps, Context context)
    {
        this.parkingList = apps;
        this.context = context;
        arraylist = new ArrayList<ClassListItems>();
        arraylist.addAll(parkingList);
    }

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

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

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

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) // inflating the layout and initializing widgets
    {

        View rowView = convertView;
        ViewHolder viewHolder= null;
        if (rowView == null)
        {
            LayoutInflater inflater = getLayoutInflater();
            rowView = inflater.inflate(R.layout.list_content, parent, false);
            viewHolder = new ViewHolder();
            viewHolder.textName = (TextView) rowView.findViewById(R.id.textName);
            viewHolder.imageView = (ImageView) rowView.findViewById(R.id.imageView);
            rowView.setTag(viewHolder);
        }
        else
        {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        // here setting up names and images
        viewHolder.textName.setText(parkingList.get(position).getName()+"");
        Picasso.with(context).load(parkingList.get(position).getImg()).into(viewHolder.imageView);

        return rowView;
    }
}

}