Thursday, 26 December 2013

Expandable List View simple example

1. Create a new project in the Eclipse IDE from File ⇒ Android Application Project and fill all required details. I left my main activity name as MainActivity.java
2. In order to create an expandable list view, we need three xml layout files. First one is for main listview, 2nd one for list view group item and 3rd one is for list view child item. Open your activity_main.xmland add ExpandableListView element.
activity_main.xml
<?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"
    android:orientation="vertical"
    android:background="#f4f4f4" >
 
            <ExpandableListView
                android:id="@+id/lvExp"
                android:layout_height="match_parent"
                android:layout_width="match_parent"/>  
 
</LinearLayout>
3. Create another xml layout for list view group header. I created an xml file named list_group.xmland pasted following code.
list_group.xml
<?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="wrap_content"
    android:orientation="vertical"
    android:padding="8dp"
    android:background="#000000">
 
 
    <TextView
        android:id="@+id/lblListHeader"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="?android:attr/expandableListPreferredItemPaddingLeft"
        android:textSize="17dp"
        android:textColor="#f9f93d" />
 
</LinearLayout>
4.Create one more xml file named list_item.xml for child list item. This will contain simple TextView element.
list_item.xml
<?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="55dip"
    android:orientation="vertical" >
 
    <TextView
        android:id="@+id/lblListItem"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textSize="17dip"
        android:paddingTop="5dp"
        android:paddingBottom="5dp"
        android:paddingLeft="?android:attr/expandableListPreferredChildPaddingLeft" />
 
</LinearLayout>
5. I am using a custom adapter class to create list view. Create a new class file calledExpandableListAdapter.java and extend this from BaseExpandableListAdapter. This class provides required methods to render listview.
getGroupView() – Returns view for the list group header
getChildView() – Returns view for list child item
ExpandableListAdapter.java
package info.androidhive.expandablelistview;
 
import java.util.HashMap;
import java.util.List;
 
import android.content.Context;
import android.graphics.Typeface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;
 
public class ExpandableListAdapter extends BaseExpandableListAdapter {
 
    private Context _context;
    private List<String> _listDataHeader; // header titles
    // child data in format of header title, child title
    private HashMap<String, List<String>> _listDataChild;
 
    public ExpandableListAdapter(Context context, List<String> listDataHeader,
            HashMap<String, List<String>> listChildData) {
        this._context = context;
        this._listDataHeader = listDataHeader;
        this._listDataChild = listChildData;
    }
 
    @Override
    public Object getChild(int groupPosition, int childPosititon) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .get(childPosititon);
    }
 
    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }
 
    @Override
    public View getChildView(int groupPosition, final int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {
 
        final String childText = (String) getChild(groupPosition, childPosition);
 
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.list_item, null);
        }
 
        TextView txtListChild = (TextView) convertView
                .findViewById(R.id.lblListItem);
 
        txtListChild.setText(childText);
        return convertView;
    }
 
    @Override
    public int getChildrenCount(int groupPosition) {
        return this._listDataChild.get(this._listDataHeader.get(groupPosition))
                .size();
    }
 
    @Override
    public Object getGroup(int groupPosition) {
        return this._listDataHeader.get(groupPosition);
    }
 
    @Override
    public int getGroupCount() {
        return this._listDataHeader.size();
    }
 
    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }
 
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded,
            View convertView, ViewGroup parent) {
        String headerTitle = (String) getGroup(groupPosition);
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this._context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.list_group, null);
        }
 
        TextView lblListHeader = (TextView) convertView
                .findViewById(R.id.lblListHeader);
        lblListHeader.setTypeface(null, Typeface.BOLD);
        lblListHeader.setText(headerTitle);
 
        return convertView;
    }
 
    @Override
    public boolean hasStableIds() {
        return false;
    }
 
    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
}
6. Once you are done with customer adapter, open your MainActivity.java and do the following changes. In the following I created required data needed for list view and passed it to custom adapter.
MainActivity.java
package info.androidhive.expandablelistview;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.ExpandableListView.OnGroupClickListener;
import android.widget.ExpandableListView.OnGroupCollapseListener;
import android.widget.ExpandableListView.OnGroupExpandListener;
import android.widget.Toast;
 
public class MainActivity extends Activity {
 
    ExpandableListAdapter listAdapter;
    ExpandableListView expListView;
    List<String> listDataHeader;
    HashMap<String, List<String>> listDataChild;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        // get the listview
        expListView = (ExpandableListView) findViewById(R.id.lvExp);
 
        // preparing list data
        prepareListData();
 
        listAdapter = new ExpandableListAdapter(this, listDataHeader, listDataChild);
 
        // setting list adapter
        expListView.setAdapter(listAdapter);
    }
 
    /*
     * Preparing the list data
     */
    private void prepareListData() {
        listDataHeader = new ArrayList<String>();
        listDataChild = new HashMap<String, List<String>>();
 
        // Adding child data
        listDataHeader.add("Top 250");
        listDataHeader.add("Now Showing");
        listDataHeader.add("Coming Soon..");
 
        // Adding child data
        List<String> top250 = new ArrayList<String>();
        top250.add("The Shawshank Redemption");
        top250.add("The Godfather");
        top250.add("The Godfather: Part II");
        top250.add("Pulp Fiction");
        top250.add("The Good, the Bad and the Ugly");
        top250.add("The Dark Knight");
        top250.add("12 Angry Men");
 
        List<String> nowShowing = new ArrayList<String>();
        nowShowing.add("The Conjuring");
        nowShowing.add("Despicable Me 2");
        nowShowing.add("Turbo");
        nowShowing.add("Grown Ups 2");
        nowShowing.add("Red 2");
        nowShowing.add("The Wolverine");
 
        List<String> comingSoon = new ArrayList<String>();
        comingSoon.add("2 Guns");
        comingSoon.add("The Smurfs 2");
        comingSoon.add("The Spectacular Now");
        comingSoon.add("The Canyons");
        comingSoon.add("Europa Report");
 
        listDataChild.put(listDataHeader.get(0), top250); // Header, Child data
        listDataChild.put(listDataHeader.get(1), nowShowing);
        listDataChild.put(listDataHeader.get(2), comingSoon);
    }
}


Run your project, you should see following output. (Note: The list view group indicators might change depending upon your android version)
android expandable list view

ListView child item click listener

Detecting the child item click can be done by implementing setOnChildClickListener listener on listview.
// Listview on child click listener
        expListView.setOnChildClickListener(new OnChildClickListener() {
 
            @Override
            public boolean onChildClick(ExpandableListView parent, View v,
                    int groupPosition, int childPosition, long id) {
                Toast.makeText(
                        getApplicationContext(),
                        listDataHeader.get(groupPosition)
                                + " : "
                                + listDataChild.get(
                                        listDataHeader.get(groupPosition)).get(
                                        childPosition), Toast.LENGTH_SHORT)
                        .show();
                return false;
            }
        });

Listening when group is expanded

You may want to execute some lines of code when the listview group is expanded. For this you can usesetOnGroupExpandListener which triggers an event when listview group expanded.
// Listview Group expanded listener
expListView.setOnGroupExpandListener(new OnGroupExpandListener() {
 
    @Override
    public void onGroupExpand(int groupPosition) {
        Toast.makeText(getApplicationContext(),
                listDataHeader.get(groupPosition) + " Expanded",
                Toast.LENGTH_SHORT).show();
    }
});

Listening when group is collapsed

Implementing setOnGroupCollapseListener will trigger an event when listview group is collapsed.
// Listview Group collasped listener
expListView.setOnGroupCollapseListener(new OnGroupCollapseListener() {
 
    @Override
    public void onGroupCollapse(int groupPosition) {
        Toast.makeText(getApplicationContext(),
                listDataHeader.get(groupPosition) + " Collapsed",
                Toast.LENGTH_SHORT).show();
 
    }
});

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