如何在Android上实现Material Design展开/折叠列表？

Question

我希望实现这种风格的材料清单.我该如何在Android上执行此操作？我应该看什么课？是否有任何现有的库可以轻松实现这一点？

Answer 1

是的,您可以使用库SectionedRecyclerViewAdapter轻松实现它.有一个完整的工作示例在这里.

基本上你创建一个section类:

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();
            }
        });
    }
}

然后使用您的部分设置RecyclerView:

// 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);

Answer 2

我使用这个库实现了这样一个列表：
expandable-recycler-view

有一个相关的博客，但它引用的是旧版本：
Expand a RecyclerView in Four Steps

它基本上是一个适配器，您可以在其中提供包含子元素的父元素列表。您还必须为父母和孩子指定两个持有者。有关更多详细信息，请参阅图书馆的页面。

class MyChild {
  // add data
}
class MyParentListItem implements ParentListItem {
  private final List<MyChild> mChildren;

  MyParentListItem(List<MyChild> children) {
    mChildren = children;
    // add other data
  }

  @Override
  public List<MyChild> getChildItemList() {
    return mChildren;
  }

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

class MyParentViewHolder extends ParentViewHolder {
  MyParentViewHolder(View itemView) {
    super(itemView);
    // get other views with itemView.findViewById(..);
  }
}

class MyChildViewHolder extends ChildViewHolder {
  MyParentViewHolder(View itemView) {
    super(itemView);
    // get other views with itemView.findViewById(..);
  }
}

public class MyExpandableAdapter extends ExpandableRecyclerAdapter<MyParentViewHolder, MyChildViewHolder> {
  private final LayoutInflater mInflater;
  public MyExpandableAdapter(List<MyParentListItem> parentItemList, Context context) {
    super(parentItemList);
    mInflater = LayoutInflater.from(context);
  }

  @Override
  public MyParentViewHolder onCreateParentViewHolder(ViewGroup parentViewGroup) {
    final View itemView = mInflater.inflate(R.layout.parent_layout, parentViewGroup, false);
    return new MyParentViewHolder(itemView);
  }

  @Override
  public MyChildViewHolder onCreateChildViewHolder(ViewGroup childViewGroup) {
    final View itemView = mInflater.inflate(R.layout.child_layout, childViewGroup, false);
    return new MyChildViewHolder(itemView);
  }

  // bind data to holders in the onBind methods
}