Question

I have an application that fetches announcements stored as xml files on a server and loads the title and author of each announcement into a ListView item. What I also need to store with each item is the ID of each announcement but I don’t actually need to display it. I thought about maybe storing the ID in the hash map I use to fill the list and then find the associated ID with the title clicked but I think it would be unsafe to use since two announcements could have the same title (and author and date). I also thought about adding an invisible TextView to each item to store the ID but that was causing layout problems. Lastly, I searched around and found setTag() and getTag() which I think would be perfect for what I want to do but I’m not really sure how to use them with SimpleAdapter (I’m relatively new to this…). If the TextView idea is what I need to do (though I doubt it), here is the layout I’m using for each item:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <TextView
      android:id="@android:id/text1"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:layout_marginLeft="6dip"
      android:textAppearance="?android:attr/textAppearanceMedium"/>
    <LinearLayout 
        android:orientation="horizontal"
        android:id="@+id/items"
        android:weightSum="100"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
        <TextView
          android:id="@android:id/text2"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginLeft="6dip"
          android:textAppearance="?android:attr/textAppearanceSmall"
          android:layout_weight="85"/>
        <LinearLayout 
            android:orientation="vertical"
            android:id="@+id/itemCB"
            android:layout_weight="15"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center">
            <CheckBox
                android:id="@+id/cbSelected"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

And I’m using the following adapter to fill the list:

for(int i = 0; i < ann.length; i++)
{
    map = new HashMap<String, String>();
    map.put("line1", ann[i].getTitle());
    map.put("line2", "Posted by: " + ann[i].getAuthor() + "\n" + ann[i].date.toLongString());
    list.add(map);
}
String[] from = { "line1", "line2"};

int[] to = { android.R.id.text1, android.R.id.text2};

SimpleAdapter adapter = new SimpleAdapter(this, list, R.layout.twoline_checkbox_id_listitem, from, to);
setListAdapter(adapter);

Thank you for any help!

Answer 1

Theoretically you could do either approaches and it will probably work without problems. In the long run however, I would say you’ll be better of with a simple entity object and a custom adapter. More specifically, from the looks of it, I would opt for an ArrayAdapter, and you already seem to be using some sort of simple entity object for the array ann.

There are tons of examples that can show you how to extend ArrayAdapter. The most important part however is the getView() method, which in it’s most basic form could look somewhat like this:

public View getView(int position, View convertView, ViewGroup parent) {
    View row;
    if (null == convertView) {
        row = mInflater.inflate(R.layout.list_item, null);
    } else {
        row = convertView;
    }

    MyObject item = (MyObject) getItem(position);

    TextView tv = (TextView) row.findViewById(android.R.id.xxx);
    tv.setText(item.getTitle);

    // same for other fields/views; e.g. author, date etc

    return row;
}

In stead of creating a SimpleAdapter, now create an instance of your CustomAdapter, pass it your array (or list) of entity objects, and set the whole as adapter to your list:

MyObject[] objects = ...
setListAdapter(new ArrayAdapter<string>(this, R.layout.list_item, objects));

Since you’re now dealing with the objects directly, in stead of first creating a bunch of strings representation out of the different fields, you can also easily access the ‘id’ of every item. Even better, you can add a whole lot of different fields without worrying how it will look like in the list, since the visual representation is determined by what you set (and don’t set) in the getView() method of your adapter.