Question

I’ve to make an application that shows information about a F1 race. In order to display this information I’ve used a ListView with several SimpleAdapters that show different data sets (one position, name, time; another each sector time…).

adaptadorPortrait1 = new SimpleAdapter(
    getApplicationContext(),
    lista_adaptador,
    R.layout.portrait1,
    new String[] {"pos", "short_name", "time_total", "time_pred"},
    new int[] {R.id.pos, R.id.name, R.id.time,R.id.prev});
adaptadorPortrait2 = new SimpleAdapter(
    getApplicationContext(),
    lista_adaptador,
    R.layout.portrait2,
    new String[] {"pos", "short_name", "sect1","sect1","sect3"},
    new int[] {R.id.pos, R.id.name, R.id.psect, R.id.ssect, R.id.tsect});
 [...]

When some events such as slice a finger over the screen or to rotate the mobile, occur, I change the list adapter.

Now I want to add a header to the list to indicate what is each column and I need that this header changes at the same time that adapter does. I have tried to use the ´addHeaderView´ method but the app fails and it throws an IllegalStateException with the message “Cannot add header view to list — setAdapter has already been called.”

Any ideas?

PS: Please excuse my bad English.

Answer 1

ListViews support multiple types of views within a single Adapter.

If you override the adapter.getItemTypeCount and adapter.getItemType(int position) methods, you can add headers in-line with the rest of your views. So, the first item within each of your adapters would be your “header” type of view (maybe a simple TextView) and the rest could be your list entries.

You’d just have to make sure that getItemType returns a different number depending on whether the position (which for a header would be 0) is a header or not.

public static final int TYPE_HEADER = 0;
public static final int TYPE_CONTENT = 1;

public int getItemTypeCount(){
     return 2;
}

public int getItemType(int position){
    if(position == 0){
        return TYPE_HEADER;
    } else {
        return TYPE_CONTENT;
    }
}

public View getView(int position, View convertView, ViewGroup parent){
    // make sure that from here, you return the right kind of view based on getItemType(position)
    // you are guaranteed that if a convertView is passed to you (convertView != null)
    // that the convertView is of the appropriate type.

    int type = getItemType(position);
    if(type == TYPE_HEADER){
        // create (or reuse) and return a header view
    } else {
        // create (or reuse) and return a content view
    }

    return myView;

}