ExpandableRecyclerView

Make an expandable list view by RecyclerView with support for multiple view types in Android.

Download

ExpandableRecyclerView:

compile 'com.thoughtbot:expandablerecyclerview:1.3'

Usage

Let's say you are a Father and you have to build an app to show a list of your child members Parents with a list of their children Childs.

First, define your custom ExpandableGroup class:

public class Parent extends ExpandableGroup<Artist> {

  public Parent(String title, List<Child> items) {
    super(title, items);
  }
}

Next up, let's create the ChildViewHolder and ParentViewHolder. These are both wrappers around regular ol' RecyclerView.ViewHolders so implement any view inflation and binding methods you may need.

public class ParentViewHolder extends GroupViewHolder

  private TextView parent_name;

  public ParentViewHolder(View itemView) {
    super(itemView);
    parent_name = itemView.findViewById(R.id.parent_name);
  }

  public void setParentName(ExpandableGroup group) {
    parent_name.setText(group.parentName());
  }
}

public class childViewHolder extends ChildViewHolder {

  private TextView child_name;

  public childViewHolder(View itemView) {
    super(itemView);
    child_name = itemView.findViewById(R.id.child_name);
  }

  public void onBind(Child child) {
    child_name.setText(child.getChildName());
  }
}

Now we are ready for the juicy part - let's make our ExpandableRecyclerViewAdapter

By including your ParentViewHolder and ChildViewHolder in the definition of the class, you'll see that the onCreateGroupViewHolder and onCreateChildViewHolder methods return the correct type 👍

public class ParentAdapter extends ExpandableRecyclerViewAdapter<ParentViewHolder, ChildViewHolder> {

  public ParentAdapter(List<? extends ExpandableGroup> groups) {
    super(groups);
  }

  @Override
  public ParentViewHolder onCreateGroupViewHolder(ViewGroup parent, int viewType) {
    View view = inflater.inflate(R.layout.list_item_parent, parent, false);
    return new ParentViewHolder(view);
  }

  @Override
  public ChildViewHolder onCreateChildViewHolder(ViewGroup parent, int viewType) {
    View view = inflater.inflate(R.layout.list_item_child, parent, false);
    return new ChildViewHolder(view);
  }

  @Override
  public void onBindChildViewHolder(ChildViewHolder holder, int flatPosition, ExpandableGroup group,
      int childIndex) {
    final Child child = ((Child) group).getItems().get(childIndex);
    holder.setchildName(child.getChildName());
  }

  @Override
  public void onBindGroupViewHolder(ParentViewHolder holder, int flatPosition,
      ExpandableGroup group) {
    holder.setParentName(group);
  }
}

Lastly let's you'll need either an Activity or Fragment to host your adapter. Once you've got that up and running, all that's left if to instantiate your fancy new ParentAdapter with a List<Parent>

public class ParentActivity extends Activity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {

    ...

    List<Parent> parents = getParents();
    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
    LinearLayoutManager layoutManager = new LinearLayoutManager(this);

    //instantiate your adapter with the list of genres
    ParentAdapter adapter = new ParentAdapter(genres);
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setAdapter(adapter);

    ...

  }
}

Saving And Restoring Expand / Collapse State

If you want to save the expand and collapse state of your adapter, you have to explicitly call through to the adapters onSaveInstanceState() and onRestoreInstanceState()in the calling Activity

public class ParentActivity extends Activity {

  ...

  @Override
  protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    adapter.onSaveInstanceState(outState);
  }

  @Override
  protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    adapter.onRestoreInstanceState(savedInstanceState);
  }
}

Adding Custom Expand / Collapse Animations

If you want to add a custom Drawable that animates based on a groups state, override the expand() and collapse() methods in your ParentpViewHolder:

public class ParentpViewHolder extends GroupViewHolder {

  ...

  @Override
  public void expand() {
    animateExpand();
  }

  @Override
  public void collapse() {
    animateCollapse();
  }
}

Listening to Expand/Collapse events

If you want register an ExpandCollapseListener outside of the adapter, you can simply call setOnGroupExpandCollapseListener on the ExpandableRecyclerViewAdapter

  adapter.setOnGroupExpandCollapseListener(new GroupExpandCollapseListener() {
    @Override
    public void onGroupExpanded(ExpandableGroup group) {

    }

    @Override
    public void onGroupCollapsed(ExpandableGroup group) {

    }
  });

Authors

• Haider Ali

Contact Me

if you have any query or want to discuss some thing realted to project or anything else please feel free to contact me.

Gmail: ihaiderali.arif@gmail.com
Skype: haider7577 
Linked in: https://www.linkedin.com/in/haider-ali-203ab7126/