ExpandableLists in Android, I want to allow only one parent list to expand at a time

Question

I want to make only one item in the parent list expand at a time, my code for the onCreate is currently the following. (It works as I want, But the method to allow only one parent open at a time doesnt work)

public void onCreate(Bundle savedInstanceState) {
        try{
             super.onCreate(savedInstanceState);
             setContentView(R.layout.main);

        final SimpleExpandableListAdapter expListAdapter =
            new SimpleExpandableListAdapter(
                        //FOR LEVEL 1 SCREEN
                    this,
                    createGroupList(),              // METHOD TO CREATE PARENTLIST Creating group List.
                    R.layout.group_row,             // REF TO XML FILENAME.         
                    new String[] { "Group Item" },  // STRING ARRAY HOLDING ONE KEY THAT REF'S ALL PARENT LIST ITEMS.
                    new int[] { R.id.row_name },    // REF TO I.D. OF PARENT XML. ID of each group item.-Data under the key goes into this TextView.                    
                    createChildList(),              // METHOD TO CREATE CHILD LST. childData describes second-level entries.
                    R.layout.child_row,             // XMLFILE NAME FOR CHILD LIST.Layout for sub-level entries(second level).
                    new String[] {"Sub Item"},      // KEY FOR CHILD ITEMS IN HASHMAP. Keys in childData maps to display.
                    new int[] { R.id.grp_child}     // XML ID FOR TEXTVIEW. Data under the keys above go into these TextViews.
                );
            setListAdapter( expListAdapter );       // setting the adapter in the list.

        //**THIS IS WHAT I DONT KNOW HOW TO CODE:**


            list = (ExpandableListView) findViewById(R.id.row_name);
            list.setAdapter( expListAdapter);
            list.setGroupIndicator(null);


            list.setOnGroupExpandListener(new OnGroupExpandListener() {

                public void onGroupExpand(int groupPosition) {
                    int len = expListAdapter.getGroupCount();
                    for (int i = 0; i < len; i++) {
                        if (i != groupPosition) {
                            list.collapseGroup(i);
                        }
                    }
                }
            });

        }catch(Exception e){

            System.out.println("Errrr +++ " + e.getMessage());
        }
    }

I understand the above code, However, I dont use expandableListViews, Im refferncing my program to my .xml files with the layouts of the expandablelist. And so I dont know how to apply the above to my program...

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
 <ExpandableListView android:id="@+id/list"
               android:layout_width="fill_parent" 
               android:layout_height="fill_parent"
               android:background="@drawable/bkg"/>

     <TextView android:id="@+id/android:empty"
               android:layout_width="fill_parent" 
               android:layout_height="fill_parent"
               android:text="No items"/>
</LinearLayout>

The method that I dont know how to apply is the following:

                    list = (ExpandableListView) findViewById(R.id.row_name);
            list.setAdapter( expListAdapter);
            list.setGroupIndicator(null);

            list.setOnGroupExpandListener(new OnGroupExpandListener() {
                    public void onGroupExpand(int groupPosition) {
                    int len = expListAdapter.getGroupCount();
                    for (int i = 0; i < len; i++) {
                        if (i != groupPosition) {
                            list.collapseGroup(i);
                        }
                    }
                }
            });

1) how do I refference the 'list' to my expandablelist activity?

list is defined in the class as private ExpandableListView list;

I do not have any errors right now, But the method does not work.

Any help is greatly appreciated!

Answer 1

// Declare variable 
private static int prev = -1;
// and OnGroupExpandListener implement


 mExpandableList.setOnGroupExpandListener(new OnGroupExpandListener() {

            @Override
            public void onGroupExpand(int groupPosition) {

                if(prev!=-1)
                {

                    mExpandableList.collapseGroup(prev);    

                }
                prev=groupPosition;
            }
        });

---

Updating with updated solution

mExpandableList.setOnGroupExpandListener(new OnGroupExpandListener() {
    // Keep track of previous expanded parent
    int previousGroup = -1;

    @Override
    public void onGroupExpand(int groupPosition) {
        // Collapse previous parent if expanded.
        if ((previousGroup != -1) && (groupPosition != previousGroup)) {
            mExpandableList.collapseGroup(previousGroup);
        }
        previousGroup = groupPosition;
    }
});