How can I implement a Material Design Expand/Collapse List on Android?

Question

I am looking to implement a material list of this style. How can I do this on Android? What classes should I look at? Are there any existing libraries that could make implementing this easy?

Answer 1

Yes, you can easily implement it with the library SectionedRecyclerViewAdapter. There is a full working example here.

Basically you create a section class:

class MySection extends StatelessSection {      String title;     List<String> list;     boolean expanded = true; // true if you want it to be displayed expanded initially      public MySection(String title, List<String> list) {         // call constructor with layout resources for this Section header, footer and items          super(R.layout.section_header, R.layout.section_item);          this.title = title;         this.list = list;     }      @Override     public int getContentItemsTotal() {         return expanded? list.size() : 0;     }      @Override     public RecyclerView.ViewHolder getItemViewHolder(View view) {         // return a custom instance of ViewHolder for the items of this section         return new MyItemViewHolder(view);     }      @Override     public void onBindItemViewHolder(RecyclerView.ViewHolder holder, int position) {         MyItemViewHolder itemHolder = (MyItemViewHolder) holder;          // bind your view here         itemHolder.tvItem.setText(list.get(position));     }      @Override     public RecyclerView.ViewHolder getHeaderViewHolder(View view) {         return new SimpleHeaderViewHolder(view);     }      @Override     public void onBindHeaderViewHolder(RecyclerView.ViewHolder holder) {         MyHeaderViewHolder headerHolder = (MyHeaderViewHolder) holder;          // bind your header view here         headerHolder.tvItem.setText(title);          // handles the click on the header to toggle the expanded variable         headerHolder.rootView.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 expanded = !expanded;                 headerHolder.imgArrow.setImageResource(                         expanded ? R.drawable.ic_keyboard_arrow_up_black_18dp : R.drawable.ic_keyboard_arrow_down_black_18dp                 );                 sectionAdapter.notifyDataSetChanged();             }         });     } } 

Then you set up the RecyclerView with your sections:

// Create an instance of SectionedRecyclerViewAdapter  SectionedRecyclerViewAdapter sectionAdapter = new SectionedRecyclerViewAdapter();  // Create your sections with the list of data for each topic MySection topic1Section = new MySection("Attractions", attractionsList); MySection topic2Section = new MySection("Dining", diningList);  // Add your Sections to the adapter sectionAdapter.addSection(topic1Section); sectionAdapter.addSection(topic2Section);  // Set up your RecyclerView with the SectionedRecyclerViewAdapter RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview); recyclerView.setLayoutManager(new LinearLayoutManager(getContext())); recyclerView.setAdapter(sectionAdapter);