Question

I am trying to modify the sample code below. It currently populates a View that contains an imageview and a textview. I have added an additional textview to my XML layout and am trying to figure out how to replace the simple array with a hash map or even a multidimensional array to populate not just the imageview and the first textview but also the second one.

I would appreciate sample code that shows the entire process. Thanks!

public class DynamicDemo extends ListActivity { 
  TextView selection; 
  private static final String[] items={"lorem", "ipsum", "dolor", 
          "sit", "amet"}
  @Override 
  public void onCreate(Bundle icicle) { 
    super.onCreate(icicle); 
    setContentView(R.layout.main); 
    setListAdapter(new IconicAdapter()); 
    selection=(TextView)findViewById(R.id.selection); 
  } 

  public void onListItemClick(ListView parent, View v, 
                             int position, long id) { 
   selection.setText(items[position]); 
  } 

  class IconicAdapter extends ArrayAdapter<String> { 
    IconicAdapter() { 
      super(DynamicDemo.this, R.layout.row, R.id.label, items); 
    } 

    public View getView(int position, View convertView, 
                       ViewGroup parent) { 
      View row=super.getView(position, convertView, parent); 
      ImageView icon=(ImageView)row.findViewById(R.id.icon); 

      if (items[position].length()>4) { 
        icon.setImageResource(R.drawable.delete); 
      } 
      else { 
        icon.setImageResource(R.drawable.ok); 
      } 

      return(row); 
    } 
  }
} 

Answer 1

The easiest thing to do is use an ArrayAdapter<MyDataObject> where

 public class MyDataObject {
      public String string1;
      public String string2;
      // any other useful attributes

 }

And then you would change items to a MyDataObject[] items stored in your class, and instead of doing super.getView(index) you’d do items[index] (which would yield a MyDataObject) and use that data instead.

Also, importantly: you should use the convertView. And possibly the ViewHolder pattern.

Edit: At OP’s request, a little more elaboration. Note that this uses the convertView pattern but not the ViewHolder pattern (you should be able to adopt that fairly easily).

In your Adapter, you’d change getView() as follows:

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

  ViewGroup row;
  if(convertView == null){
      // create your view here.
      row = getLayoutInflater().inflate(R.layout.row);   
  } else {
      row = convertView;
  }

  // note:  when you implement ViewHolder, the ViewHolder will
  // hold this reference so that you don't need to look it up every time.
  ImageView icon=(ImageView)row.findViewById(R.id.icon); 

  // here you're employing the "items" array that you were using 
  // before, except now it contains MyDataObjects.  pick out the 
  // string (or other data you want to check) from the resulting MyDataObject, 
  // and see if it's longer than 4 characters.

  MyDataObject objectAtThisPosition = items[position];

  if (objectAtThisPosition.string1.length()>4) { 
    icon.setImageResource(R.drawable.delete); 
  } 
  else { 
    icon.setImageResource(R.drawable.ok); 
  } 

  // Do whatever else you want to with objectAtThisPosition.

  return(row); 
} 

That’s it for the easy way, and quite similar to what you have.

Some more detail; if you don’t care, skip it. 🙂

I know that Adapters can seem magical, so in the interest of showing how ListView adapters work, here’s an example using a List instead of an Array, so we can remove any magic that ArrayAdapter does with the array behind the scenes. I use a List because they can be more versatile for whatever you’re trying to accomplish (ArrayList or LinkedList or what-have-you).

To use a List you’d have the following in your Activity:

 private List<MyDataObject> myList = new ArrayList<MyDataObject>();

And instead of items[position] you’d use

 MyDataObject objectAtThisPosition = myList.get(position);

If you want to change your data set dynamically, you should probably use this approach (keeping myList at the Activity level) instead of using an Array and an ArrayAdapter. That would mean you’d need to change from extending ArrayAdapter<String> to just extending BaseAdapter<MyDataObject> (most of the methods in BaseAdapter are trivial to implement) since our data size, for example, would be determined by our list, and not the ArrayAdapter‘s array.

I know that’s kind of a fire hose, but let me know if you have any questions!