Implementing Expandable Recycler View in Android Application

Expandable Recycler view is alternative of ExpandableListView. There are many times when ExapandableListView don’t perform as per the requirement. It fails in the coordinator layout as well as have layout height issue.

Thus we are creating a simple Expandable Recycle view using bignerdranch’s expandablerecyclerview library.

Dependency used in this blog:

compile ‘com.bignerdranch.android:expandablerecyclerview:2.1.1’

1. Custom Parent and Child Classed used to represent the relationship

SubcategoryParentListItem is our parent class that is used to store the data relevant to parent.

    class SubcategoryParentListItem implements ParentListItem {
        private String mTitle;
        private List<SubcategoryChildListItem> mChildItemList;

        public SubcategoryParentListItem() {
            mTitle = "SubcategoryParentListItem";
        }

        @Override
        public List<SubcategoryChildListItem> getChildItemList() {
            return mChildItemList;
        }

        public void setChildItemList(List<SubcategoryChildListItem> list) {
            mChildItemList = list;
        }

        @Override
        public boolean isInitiallyExpanded() {
            return false;
        }
    }

class SubcategoryParentListItem implements ParentListItem {

private String mTitle;

private List<SubcategoryChildListItem> mChildItemList;

public SubcategoryParentListItem() {

mTitle = "SubcategoryParentListItem";

}

@Override

public List<SubcategoryChildListItem> getChildItemList() {

return mChildItemList;

}

public void setChildItemList(List<SubcategoryChildListItem> list) {

mChildItemList = list;

}

@Override

public boolean isInitiallyExpanded() {

return false;

}

SubcategoryChildListItem is our simple child class used to display the content in each child of parent

    public class SubcategoryChildListItem {

        private final String mTitle;

        public SubcategoryChildListItem() {
            mTitle = "SubcategoryChildListItem";
        }

    }

public class SubcategoryChildListItem {

private final String mTitle;

public SubcategoryChildListItem() {

mTitle = "SubcategoryChildListItem";

}

2. Preparing data for Expandable Recycler View

Creating List of parent item to be displayed in a view.

  List<SubcategoryParentListItem> subcategoryParentListItems = new ArrayList<>();
        for (int i = 0; i < 5; i++) {
            SubcategoryParentListItem eachParentItem = new SubcategoryParentListItem();
            subcategoryParentListItems.add(eachParentItem);
        }

List<SubcategoryParentListItem> subcategoryParentListItems = new ArrayList<>();

for (int i = 0; i < 5; i++) {

SubcategoryParentListItem eachParentItem = new SubcategoryParentListItem();

subcategoryParentListItems.add(eachParentItem);

}

Creating a list of child item and setting this list to a particular parent.

subcategoryParentListItem.setChildItemList(childItemList); // set the list of child item for a parent item.

  List<ParentListItem> parentListItems = new ArrayList<>();
        for (SubcategoryParentListItem subcategoryParentListItem : subcategoryParentListItems) {
            List<SubcategoryChildListItem> childItemList = new ArrayList<>();
            for (int i = 0; i < 5; i++) {
                childItemList.add(new SubcategoryChildListItem());
            }
            subcategoryParentListItem.setChildItemList(childItemList);
            parentListItems.add(subcategoryParentListItem);
        }

List<ParentListItem> parentListItems = new ArrayList<>();

for (SubcategoryParentListItem subcategoryParentListItem : subcategoryParentListItems) {

List<SubcategoryChildListItem> childItemList = new ArrayList<>();

for (int i = 0; i < 5; i++) {

childItemList.add(new SubcategoryChildListItem());

}

subcategoryParentListItem.setChildItemList(childItemList);

parentListItems.add(subcategoryParentListItem);

}

3. Setting adapter to a Recycler View to make it EXPANDABLE

 recyclerView.setAdapter(new SubCategoryExpandableRecyclerAdapter(mContext, parentListItems));

1	recyclerView.setAdapter(new SubCategoryExpandableRecyclerAdapter(mContext, parentListItems));

4. Implementing Custom adapter to support expansion of views.

Unlike traditional Recycler view in which we have a single view holder and thus single onCreateViewHolder and onBindViewHolder,
We have two different sets of onCreateViewHolder and onBindViewHolder.

      class SubCategoryExpandableRecyclerAdapter extends ExpandableRecyclerAdapter<SubCategoryExpandableRecyclerAdapter.MyParentViewHolder, SubCategoryExpandableRecyclerAdapter.MyChildViewHolder> {
        private LayoutInflater mInflater;

        public SubCategoryExpandableRecyclerAdapter(Context context, List<ParentListItem> itemList) {
            super(itemList);
            mInflater = LayoutInflater.from(context);
        }

        @Override
        public MyParentViewHolder onCreateParentViewHolder(ViewGroup viewGroup) {
            View view = mInflater.inflate(R.layout.item_subcategory_fragment_elv_group, viewGroup, false);
            return new MyParentViewHolder(view);
        }

        @Override
        public MyChildViewHolder onCreateChildViewHolder(ViewGroup viewGroup) {
            View view = mInflater.inflate(R.layout.item_subcategory_fragment_elv_child, viewGroup, false);
            return new MyChildViewHolder(view);
        }

        @Override
        public void onBindParentViewHolder(MyParentViewHolder parentViewHolder, int position, ParentListItem parentListItem) {
            SubcategoryParentListItem subcategoryParentListItem = (SubcategoryParentListItem) parentListItem;
            parentViewHolder.lblListHeader.setText(subcategoryParentListItem.mTitle);

        }

        @Override
        public void onBindChildViewHolder(MyChildViewHolder childViewHolder, int position, Object childListItem) {
            SubcategoryChildListItem subcategoryChildListItem = (SubcategoryChildListItem) childListItem;
            childViewHolder.txtListChild.setText(subcategoryChildListItem.mTitle);

        }

        public class MyParentViewHolder extends ParentViewHolder {

            public TextView lblListHeader;

            public MyParentViewHolder(View itemView) {
                super(itemView);
                lblListHeader = (TextView) itemView.findViewById(R.id.lblListHeader);
            }
        }


        public class MyChildViewHolder extends ChildViewHolder {

            public TextView txtListChild;

            public MyChildViewHolder(View itemView) {
                super(itemView);

                txtListChild = (TextView) itemView.findViewById(R.id.lblListItem);
            }
        }
    }

class SubCategoryExpandableRecyclerAdapter extends ExpandableRecyclerAdapter<SubCategoryExpandableRecyclerAdapter.MyParentViewHolder, SubCategoryExpandableRecyclerAdapter.MyChildViewHolder> {

private LayoutInflater mInflater;

public SubCategoryExpandableRecyclerAdapter(Context context, List<ParentListItem> itemList) {

super(itemList);

mInflater = LayoutInflater.from(context);

}

@Override

public MyParentViewHolder onCreateParentViewHolder(ViewGroup viewGroup) {

View view = mInflater.inflate(R.layout.item_subcategory_fragment_elv_group, viewGroup, false);

return new MyParentViewHolder(view);

}

@Override

public MyChildViewHolder onCreateChildViewHolder(ViewGroup viewGroup) {

View view = mInflater.inflate(R.layout.item_subcategory_fragment_elv_child, viewGroup, false);

return new MyChildViewHolder(view);

}

@Override

public void onBindParentViewHolder(MyParentViewHolder parentViewHolder, int position, ParentListItem parentListItem) {

SubcategoryParentListItem subcategoryParentListItem = (SubcategoryParentListItem) parentListItem;

parentViewHolder.lblListHeader.setText(subcategoryParentListItem.mTitle);

}

@Override

public void onBindChildViewHolder(MyChildViewHolder childViewHolder, int position, Object childListItem) {

SubcategoryChildListItem subcategoryChildListItem = (SubcategoryChildListItem) childListItem;

childViewHolder.txtListChild.setText(subcategoryChildListItem.mTitle);

}

public class MyParentViewHolder extends ParentViewHolder {

public TextView lblListHeader;

public MyParentViewHolder(View itemView) {

super(itemView);

lblListHeader = (TextView) itemView.findViewById(R.id.lblListHeader);

}

public class MyChildViewHolder extends ChildViewHolder {

public TextView txtListChild;

public MyChildViewHolder(View itemView) {

super(itemView);

txtListChild = (TextView) itemView.findViewById(R.id.lblListItem);

}

That’s all folks. Stay updated !

REFERENCE:
https://github.com/bignerdranch/expandable-recycler-view

Shubham Agarwal 14 December 2016

. . .

Discuss on Helpdesk

10 comments

smwaura Jun 29, 2016 at 7:11 am

How do u implement search on this Expandable Recyclerview?

Shudy Jul 4, 2016 at 9:05 am

How can be implmented “onclickListener” on child , to get all the information and pass, to another activity?

Thanks in advance

Shubham Agarwal Jul 12, 2016 at 6:52 am
You can add OnClickListener in the SubCategoryExpandableRecyclerAdapter. This is because we are binding the views using this adapter. If you want to provide listener on Child then you do this in onBindChildViewHolder() method.

childViewHolder.txtListChild.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// your logic here
}
});

Reply

InstanttPS Xceleratics Jul 11, 2016 at 7:20 am

Kindly add notify datasetchanged too….

Shubham Agarwal Nov 9, 2016 at 6:45 am

First of all i don’t think that’s a navigation view. I think that’s a fragment rather than navigation view. But if you are planning to add expandable adapter in REcycler view check out this post https://mobikul.com/create-custom-navigation-view-recycler-view/ or https://mobikul.com/implementation-mikepenzmaterialdrawer-library-navigation-view/

Gaurav meghanathi Nov 9, 2016 at 7:02 am
i also created just simple recyclerview on fragment and i want to implement expnadable recyclerview like snapdeal and yahoo some navigation item to expand not each and every item to expand. and thanks to the help.

Reply
- Shubham Agarwal Nov 9, 2016 at 7:08 am
  Yes you can make a recycler view expandable. Just use a simple Recycler view with expandable recycler adapter provided by the adapter. Expandable recycler adapter allows you to set whether to expand the item or not. All depends on child items corresponding to parent item. If it is null, it will not update automatically.
  
  Reply

sagar Dec 1, 2016 at 5:52 am

i m successfully add click listener to sub child. but how to expand those sub child, any idea, plz give some suggestion. thank you

Shubham Agarwal Dec 26, 2016 at 1:31 pm
Child are automatically expanded if child item list is neither null and nor empty.

Reply

4face Jan 9, 2017 at 7:57 pm

Hello, where is my error?

private List getGroups(){
List reminderList = RealmReminders.getReminderList(mActivity, 0);
List todayReminder = new ArrayList();
List tomorrowReminder = new ArrayList();
List otherDayReminder = new ArrayList();

for (MyReminder thisReminder : reminderList){
if (thisReminder.getRemindDay() == mThisDay) todayReminder.add(thisReminder);
else if (thisReminder.getRemindDay() == mThisDay+1) tomorrowReminder.add(thisReminder);
else if (thisReminder.getRemindDay() > mThisDay+1) otherDayReminder.add(thisReminder);
}

List list = new ArrayList();
ReminderGroup today, tomorrow, otherDay;
if (todayReminder.size() != 0) {
today = new ReminderGroup(“Today”, todayReminder);
list.add(today);
}
if (tomorrowReminder.size() != 0) {
tomorrow = new ReminderGroup(“Tomorrow”, tomorrowReminder);
list.add(tomorrow);
}
if (otherDayReminder.size() != 0) {
otherDay = new ReminderGroup(“Next”, otherDayReminder);
list.add(otherDay);
}
return list;
}

@Override
public void onBindParentViewHolder(MyParentViewHolder parentViewHolder, int position, ParentListItem parentListItem) {
ReminderGroup reminderGroup = (ReminderGroup) parentListItem;
parentViewHolder.day.setText(reminderGroup.getDay());
}

@Override
public void onBindChildViewHolder(MyChildViewHolder childViewHolder, int position, Object childListItem) {
MyReminder reminder = (MyReminder) childListItem;
etc
}

java.lang.IllegalStateException: Null object added at com.bignerdranch.expandablerecyclerview.Adapter.ExpandableRecyclerAdapter.getItemViewType(ExpandableRecyclerAdapter.java:223)

Implementing Expandable Recycler View in Android Application

1. Custom Parent and Child Classed used to represent the relationship

2. Preparing data for Expandable Recycler View

3. Setting adapter to a Recycler View to make it EXPANDABLE

4. Implementing Custom adapter to support expansion of views.

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