It may not seem like an ExpandableListAdapter

Question

I am trying to write a simple example that retrieves external data over a network and fills ExpandableListViewthrough ExpandableListAdapter. I tried a couple of examples and pretty much lost. I am familiar with working with the class ArrayAdapter, but it seems that ExpandableListAdapterWAY is different. Here is my current application code that does not display anything:

MyExpandableListAdapter

public class MyExpandableListAdapter extends BaseExpandableListAdapter {

    public static class GroupHolder {
        TextView title;
    }

    public static class ChildHolder {
        TextView title;
        ImageView icon;
    }


    // groups.getChildren() returns the children
    private List<Group> groups;

    private Context context;

    private LayoutInflater inflater;

    public MyExpandableListAdapter(Context context, List<Group> groups) {
        this.context = context;
        this.groups = groups;
        this.inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public boolean hasStableIds() {
        return true;
    }

    public Object getGroup(int groupPosition) {
        return groups.get(groupPosition);
    }

    public int getGroupCount() {
        return groups.size();
    }

    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    public View getGroupView(int groupPosition, boolean isExpanded,
            View convertView, ViewGroup parent) {
        GroupHolder holder;

        if (convertView != null) {
            holder = (GroupHolder)convertView.getTag();
        } else {
            convertView = inflater.inflate(R.layout.group_item, parent, false);

            holder = new GroupHolder();
            holder.title = (TextView) convertView.findViewById(R.id.group_item_title);

            convertView.setTag(holder);
        }

        holder.title.setText(this.groups.get(groupPosition).getName());

        return convertView;
    }

    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }

    public Object getChild(int groupPosition, int childPosition) {
        return groups.get(groupPosition).getChildren().get(childPosition);
    }

    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    public int getChildrenCount(int groupPosition) {
        return groups.get(groupPosition).getChildren().size();
    }

    public View getChildView(int groupPosition, int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {
        ChildHolder holder;

        if (convertView != null) {
            holder = (ChildHolder) convertView.getTag();
        } else {
            convertView = inflater.inflate(R.layout.child_item, parent, false);

            holder = new ChildHolder();
            holder.title = (TextView) convertView.findViewById(R.id.child_item_title);
            holder.icon = (ImageView) convertView.findViewById(R.id.child_item_icon);

            convertView.setTag(holder);
        }

        holder.title.setText(groups.get(groupPosition).getChildren().get(childPosition).getName());
//      TODO add in image loading.

        return convertView;
    }
}

MyExpandableListActivity:

public class MyExpandableListActivity extends ExpandableListActivity {

    private List<Group> groups;

    private ExpandableListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.group_list);

        this.groups = new ArrayList<Group>();
        Group group = new Group("$1", "Colors");
        Child child = new Child("$2", "Red");
        groups.getChildren().add(child);

        this.adapter = new MyExpandableListAdapter(this, groups);

        setListAdapter(this.adapter);
    }
}

R.layout.group_list:

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

    <ExpandableListView android:id="@+id/android:list"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"/>

    <TextView android:id="@+id/android:empty"
            android:text="EMPTY! DOOM!"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"/>
</LinearLayout>

R.layout.group_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="match_parent">

    <TextView android:id="@+id/group_item_title"/>
</LinearLayout>

R.layout.child_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="match_parent"
        android:orientation="horizontal">

    <ImageView android:id="@+id/child_item_icon"
            android:layout_width="48px" android:layout_height="48px"/>

    <TextView android:id="@+id/child_item_title"/>
</LinearLayout>

Of course, I see "EMPTY !!"! not the list item that I added in my activity. What am I doing wrong?

In addition, it seems that I SimpleExpandableListAdapterhave to make everything simple, but I can’t completely understand how it works or how to use it. Can someone help me figure this out?

Answer 1

: ExpandableListAdapter

Answer 2

, "fill_parent" . , . , simlar group_list. , .

Answer 3

LinearLayout group_list.xml?

, ExpandableListActivity.

, getView(), , .