如何使用LinearLayoutManager实现可扩展项目(随Android L一起推出)

Question

RecyclerView已经与Android L一起推出,是AppCompat v7库的一部分.然后我决定用这个全新的应用更新我的应用程序RecyclerView来取代我ListView的.为此,当设置一个LayoutManagerfor RecyclerView,我正在使用LinearLayoutManager,它工作正常.

这是艰难的事情:当我想改变我ExpandableListView的时候RecyclerView.由于谷歌没有创建" ExpandableLayoutManager",这是非常棘手的,我无法做到这一点.

该文件提到了儿童,但它似乎是RecyclerView儿童自己的根本观点.

有人有解决方法或一些线索吗？或至少一些信息,比如从哪里开始,以便我可以实现自己的LayoutManager.

Answer 1

该库可帮助您将项目分组为“部分”，然后您可以实现本示例中下面的展开/折叠功能。

首先创建您的部分类：

class MySection extends StatelessSection {

    String header;
    List<String> list;
    boolean expanded = true;

    public MySection(String header, List<String> list) {
        // call constructor with layout resources for this Section header and items 
        super(R.layout.section_header, R.layout.section_item);
        this.myHeader = header;
        this.myList = list;
    }

    @Override
    public int getContentItemsTotal() {
        return expanded? list.size() : 0;
    }

    @Override
    public RecyclerView.ViewHolder getHeaderViewHolder(View view) {
        return new HeaderViewHolder(view);
    }

    @Override
    public void onBindHeaderViewHolder(RecyclerView.ViewHolder holder) {
        final HeaderViewHolder headerHolder = (HeaderViewHolder) holder;

        headerHolder.tvTitle.setText(title);

        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();
            }
        });
    }

    @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));
    }
}

然后创建您的部分的实例并设置您的适配器：

// Create an instance of SectionedRecyclerViewAdapter 
SectionedRecyclerViewAdapter sectionAdapter = new SectionedRecyclerViewAdapter();

// Add your Sections
sectionAdapter.addSection(new MySection("Section 1", Arrays.asList(new String[] {"Item 1", "Item 2", "Item 3", "Item 4" })));
sectionAdapter.addSection(new MySection("Section 2", Arrays.asList(new String[] {"Item 1", "Item 2" })));

// Set up your RecyclerView with the SectionedRecyclerViewAdapter
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(sectionAdapter);