How To Save And Restore The State Of An Expandablelistview In Android?

Is it possible to save and restore the state (which items are collapsed and which not) of an ExpandableListView in Android? If it is possible, how can I do that? Can I access the

Solution 1:

I iterate through the groups and save the state of them all:

int numberOfGroups = MyExpandableListViewAdapter.getGroupCount();
boolean[] groupExpandedArray = newboolean[numberOfGroups];
  for (int i=0;i<numberOfGroups;i++)
    groupExpandedArray[i] = MyExpandableListView.isGroupExpanded(i);

Then for restore the state:

for (int i=0;i<groupExpandedArray.length;i++)
  if (groupExpandedArray[i] == true)
    MyExpandableListView.expandGroup(i);

I don't understand what you mean by how to access the ListView in onPause() / onResume(), it should be accessible from there if you store the ListView object as a member of the activity class.

Solution 2:

Improving Floaf's answer: declare

publicstaticint firstVisiblePosition=0;

on Pause

int numberOfGroups = MyExpandableListViewAdapter.getGroupCount();
boolean[] groupExpandedArray = newboolean[numberOfGroups];
for (int i=0;i<numberOfGroups;i++){
    groupExpandedArray[i] = MyExpandableListView.isGroupExpanded(i);
}
firstVisiblePosition = MyExpandableListView.getFirstVisiblePosition();

onResume

for (int i=0;i<groupExpandedArray.length;i++){
  if (groupExpandedArray[i] == true)
      MyExpandableListView.expandGroup(i);
}
MyExpandableListView.setSelection(firstVisiblePosition );

This will not only restore each group's state but it will also scroll to the childView that was viewed when activity paused.

Solution 3:

a simpler way could be, if you're using setOnGroupClickListner and setOnChildClickListener just keep the last selected ChildPosition and GroupPositin integer and later on check it and respond properly,

if (childPosition > 0) {
    mExpandableList.expandGroup(groupPositin);
}
mExpandableList.setItemChecked(groupPositin + childPosition , true);

you just need to remember set childPosition to 0 in your setOnGroupListener method.

Solution 4:

I came across this very same question and found a better answer. I have a fragment and use the onSaveInstanceState and onViewStateRestored to save and restore the ExpandableListView.

Here I save the state of the list

@OverridepublicvoidonSaveInstanceState( @NonNull Bundle outState )
{
    super.onSaveInstanceState( outState );

    ExpandableListViewexpandable= getView() != null ? getView().findViewById( R.id.expandable ) : null;
    if( expandable != null )
    {
        intgroupsCount= expandable.getExpandableListAdapter()
                                    .getGroupCount();
        boolean[] groupExpandedArray = newboolean[groupsCount];
        for( inti=0; i < groupsCount; i += 1 )
        {
            groupExpandedArray[i] = expandable.isGroupExpanded( i );
        }
        outState.putBooleanArray( "groupExpandedArray", groupExpandedArray );
        outState.putInt( "firstVisiblePosition", expandable.getFirstVisiblePosition() );
    }
}

And here I restore it when it is needed

@OverridepublicvoidonViewStateRestored( @Nullable Bundle savedInstanceState )
{
    super.onViewStateRestored( savedInstanceState );
    if( savedInstanceState != null )
    {
        boolean[]          groupExpandedArray   = savedInstanceState.getBooleanArray( "groupExpandedArray" );
        intfirstVisiblePosition= savedInstanceState.getInt( "firstVisiblePosition", -1 );
        ExpandableListViewexpandable= getView() instanceof ViewGroup ? getView().findViewById( R.id.expandable ) : null;
        if( expandable != null && groupExpandedArray != null )
        {
            for( inti=0; i < groupExpandedArray.length; i++ )
            {
                if( groupExpandedArray[i] )
                    expandable.expandGroup( i );
            }
            if( firstVisiblePosition >= 0 )
                expandable.setSelection( firstVisiblePosition );
        }
    }
}