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A question about ExpandableListViews on Android

Posted on 2011-03-08
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Last Modified: 2012-05-11
Hey,

       I'm trying to create an ExpandableListView, on the Android, I tried searching google for some tutorials... but didn't turn out with much success, the closest one I found was http://mylifewithandroid.blogspot.com/2008/05/expandable-lists.html but it wasn't much help.

What I'm trying to do, is create an ExpandableListView with only one parent, like:

--Parent
|->Child 1
|->Child 2
|->Child 3
|->etc

Is there a way to do this with ExpandableListView? Or am I looking at the wrong structure for this?

Appreciate any help on this!
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Comment
Question by:errang
  • 2
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4 Comments
 
LVL 17

Expert Comment

by:Dejan Pažin
ID: 35082860

Why is the link you posted no good? The picture in the link looks very much like your structure, so let us know why isnt it helpful.
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Author Comment

by:errang
ID: 35083269
Well, one reason is that the code snippet didnt work for me for some odd reason, and I looked up the constructors for the class so I could understand it better, but that didn't help much either.

I mainly don't get how the constructors for this are structured, in terms of linking the XML files in the right places.
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LVL 17

Accepted Solution

by:
Dejan Pažin earned 500 total points
ID: 35083992

Ok, here is a simpler example which I took from google site and adapetd to your needs a little - it shows the tree like you want it - with a single parent. This way you dont need any xml - besides the manifest of course, which runs the activity. The base code was taken from here:

http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/ExpandableList1.html


import android.app.ExpandableListActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.ContextMenu;
import android.view.Gravity;
import android.view.MenuItem;
import android.view.ContextMenu.ContextMenuInfo;
import android.widget.AbsListView;
import android.widget.BaseExpandableListAdapter;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.ExpandableListView.ExpandableListContextMenuInfo;


/**
 * Demonstrates expandable lists using a custom {@link ExpandableListAdapter}
 * from {@link BaseExpandableListAdapter}.
 */
public class MyActivity extends ExpandableListActivity {

    ExpandableListAdapter mAdapter;

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

        // Set up our adapter
        mAdapter = new MyExpandableListAdapter();
        setListAdapter(mAdapter);
        registerForContextMenu(getExpandableListView());
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
        menu.setHeaderTitle("Sample menu");
        menu.add(0, 0, 0, "test");
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        ExpandableListContextMenuInfo info = (ExpandableListContextMenuInfo) item.getMenuInfo();

        String title = ((TextView) info.targetView).getText().toString();

        int type = ExpandableListView.getPackedPositionType(info.packedPosition);
        if (type == ExpandableListView.PACKED_POSITION_TYPE_CHILD) {
            int groupPos = ExpandableListView.getPackedPositionGroup(info.packedPosition);
            int childPos = ExpandableListView.getPackedPositionChild(info.packedPosition);
            Toast.makeText(this, title + ": Child " + childPos + " clicked in group " + groupPos,
                    Toast.LENGTH_SHORT).show();
            return true;
        } else if (type == ExpandableListView.PACKED_POSITION_TYPE_GROUP) {
            int groupPos = ExpandableListView.getPackedPositionGroup(info.packedPosition);
            Toast.makeText(this, title + ": Group " + groupPos + " clicked", Toast.LENGTH_SHORT).show();
            return true;
        }

        return false;
    }

    /**
     * A simple adapter which maintains an ArrayList of photo resource Ids.
     * Each photo is displayed as an image. This adapter supports clearing the
     * list of photos and adding a new photo.
     *
     */
    public class MyExpandableListAdapter extends BaseExpandableListAdapter {
        // Sample data set.  children[i] contains the children (String[]) for groups[i].
        private String[] groups = { "Parent"};
        private String[][] children = {
                { "Child1", "Child2", "Child3", "etc..." }
        };

        public Object getChild(int groupPosition, int childPosition) {
            return children[groupPosition][childPosition];
        }

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

        public int getChildrenCount(int groupPosition) {
            return children[groupPosition].length;
        }

        public TextView getGenericView() {
            // Layout parameters for the ExpandableListView
            AbsListView.LayoutParams lp = new AbsListView.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT, 64);

            TextView textView = new TextView(MyActivity.this);
            textView.setLayoutParams(lp);
            // Center the text vertically
            textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
            // Set the text starting position
            textView.setPadding(36, 0, 0, 0);
            return textView;
        }

        public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
                View convertView, ViewGroup parent) {
            TextView textView = getGenericView();
            textView.setText(getChild(groupPosition, childPosition).toString());
            return textView;
        }

        public Object getGroup(int groupPosition) {
            return groups[groupPosition];
        }

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

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

        public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
                ViewGroup parent) {
            TextView textView = getGenericView();
            textView.setText(getGroup(groupPosition).toString());
            return textView;
        }

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

        public boolean hasStableIds() {
            return true;
        }

    }
}

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Author Closing Comment

by:errang
ID: 35090328
Ah, sweet, Thanks =)

Would'v been happy with just an explanation of how the Constructors worked though =)
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