前言

最近碰到了RecyclerView展開折疊的需求。
在CSDN上看到了一種寫法是在RecyclerView的Item布局外面嵌套了一層LinearLayout。
但是這樣子做有一個(gè)不好的地方是需要取消RecyclerView的重用機(jī)制。
后來又在同事的建議下嘗試了只使用一層RecyclerView來實(shí)現(xiàn)展開折疊的實(shí)現(xiàn)方式。
本文會(huì)把兩種寫法都記錄下來，大家可以直接去看第二種實(shí)現(xiàn)方式。
畢竟從性能等方面來考慮，只用一層RecyclerView無疑是最優(yōu)解。

（于2017.11.26更新，提供了單層RecyclerView實(shí)現(xiàn)點(diǎn)擊展開/折疊的帶數(shù)據(jù)加載、移除的寫法。）
（于2017.12.26更新，修改github指向地址。增加首發(fā)說明。）

本文由作者三汪首發(fā)于簡(jiǎn)書。
本文demo已上傳Github→戳這里

效果展示

一、嵌套實(shí)現(xiàn)

1.要點(diǎn)說明

• 要記得在onCreateViewHolder()中取消Recycler的重用機(jī)制viewHolder.setIsRecyclable(false); 否則會(huì)出現(xiàn)重復(fù)添加子布局和在未點(diǎn)擊展開時(shí)展開子布局的情況。
• 代碼中使用了item外嵌套的LinearLayout的setTag()、getTag()來判斷當(dāng)前點(diǎn)擊要觸發(fā)的動(dòng)作是展開還是折疊。當(dāng)item離開當(dāng)前屏幕時(shí)就會(huì)被銷毀，因此Tag的值也就不存在了。

2.代碼展示(僅展示主要代碼)

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = (RecyclerView) findViewById(R.id.recycler_main);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        MainRecyclerViewAdapter recyclerAdapter = new MainRecyclerViewAdapter();
        recyclerView.setAdapter(recyclerAdapter);

        button = (Button) findViewById(R.id.button_main);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,TwoActivity.class);
                startActivity(intent);
            }
        });
    }
}

MainRecyclerViewAdapter.java

public class MainRecyclerViewAdapter extends RecyclerView.Adapter<MainRecyclerViewAdapter.MainRecyclerViewHolder> {


    @Override
    public MainRecyclerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View item = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler,parent,false);
        MainRecyclerViewHolder viewHolder = new MainRecyclerViewHolder(item);
        viewHolder.setIsRecyclable(false);//取消viewHolder的重用機(jī)制。沒有這句話子布局subView會(huì)被重復(fù)添加。

        return viewHolder;
    }

    @Override
    public void onBindViewHolder(MainRecyclerViewHolder holder, int position) {

    }

    @Override
    public int getItemCount() {
        return 20;
    }


    protected class MainRecyclerViewHolder extends RecyclerView.ViewHolder {

        private TextView textTime, textPrice;

        public MainRecyclerViewHolder(View itemView) {
            super(itemView);
            textTime = itemView.findViewById(R.id.text_first_time);
            textPrice = itemView.findViewById(R.id.text_first_price);
            //item點(diǎn)擊事件監(jiān)聽
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    int flag = 1;//用于判斷當(dāng)前是展開還是收縮狀態(tài)
                    //獲取外層linearlayout布局
                    LinearLayout linearLayout = view.findViewById(R.id.main_tree_root_layout);
                    //new一個(gè)RecyclerView來當(dāng)展開的子布局。
                    RecyclerView subView = new RecyclerView(view.getContext());
                    SubViewAdapter adapter = new SubViewAdapter();
                    subView.setLayoutManager(new LinearLayoutManager(view.getContext()));
                    subView.setAdapter(adapter);
                    //當(dāng)flag不為空的時(shí)候,獲取flag的值。
                    if (linearLayout.getTag() != null) {
                        flag = (int) linearLayout.getTag();
                    }
                    //當(dāng)flag為1時(shí)，添加子布局。否則，移除子布局。
                    if (flag == 1) {
                        linearLayout.addView(subView);
                        subView.setTag(101);
                        linearLayout.setTag(2);
                    } else {
                        linearLayout.removeView(view.findViewWithTag(101));
                        linearLayout.setTag(1);
                    }
                }
            });
        }
    }

    //subView的adapter
    private class SubViewAdapter extends RecyclerView.Adapter{

        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            return new SubViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler_detail,parent,false));
        }

        @Override
        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

        }

        @Override
        public int getItemCount() {
            return 5;
        }

        private class SubViewHolder extends RecyclerView.ViewHolder{
            private SubViewHolder(View itemView){
                super(itemView);
            }
        }
    }
}

二、單層RecyclerView實(shí)現(xiàn)

1.要點(diǎn)說明

• 當(dāng)前寫法采用了兩個(gè)SparseArray來分別保存第一級(jí)布局和第二級(jí)布局的數(shù)據(jù)對(duì)象。
• 第一級(jí)布局的數(shù)據(jù)對(duì)象中增加了isExpand字段來標(biāo)志當(dāng)前布局是否被點(diǎn)擊展開過，以及增加了addedSubNum字段來儲(chǔ)存點(diǎn)擊展開后新增的item個(gè)數(shù)。
• 點(diǎn)擊折疊移除數(shù)據(jù)時(shí)，由于SparseArray的特性，必須使用一個(gè)新的SparseArray來作為中轉(zhuǎn)，暫時(shí)保存需要修改key的數(shù)據(jù)。等remove動(dòng)作做完以后再重新put回原來的SparseArray。

2.代碼展示(僅展示主要代碼)

TheFirstBean.java

/**
 * 第一層布局?jǐn)?shù)據(jù)bean
 * Created by 2dog on 2017/11/26.
 */

public class TheFirstBean {
    private boolean isExpand = false;
    private int addedSubNum;

    public TheFirstBean() {
    }

    public void setExpand(boolean expand) {

        isExpand = expand;
    }

    public void setAddedSubNum(int addedSubNum) {
        this.addedSubNum = addedSubNum;
    }

    public boolean isExpand() {
    
        return isExpand;
    }

    public int getAddedSubNum() {
        return addedSubNum;
    }
}

TwoActivity.java

public class TwoActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_two);
        //數(shù)據(jù)初始化
        List<TheFirstBean> list = new ArrayList<>();
        for (int i = 0; i<20;i++){
            list.add(new TheFirstBean());
        }
        //設(shè)置RecyclerView
        recyclerView = (RecyclerView) findViewById(R.id.recycler_two);
        recyclerView.setAdapter(new TwoRecyclerViewAdapter(list));
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
    }

}

TwoRecyclerViewAdapter .java

/**
 * 使用一層recyclerView實(shí)現(xiàn)點(diǎn)擊展開二層布局效果
 * Created by wolfgy on 2017/10/16.
 */

public class TwoRecyclerViewAdapter  extends RecyclerView.Adapter {

    private SparseArray<TheFirstBean> firstBeanSparseArray = new SparseArray<>();//存儲(chǔ)每日流水?dāng)?shù)據(jù)
    private SparseArray<TheSecondBean> secondBeanSparseArray = new SparseArray<>();//存儲(chǔ)每條流水?dāng)?shù)據(jù)
    private static final int TYPE_FIRST = 0;//第一層布局
    private static final int TYPE_SECOND = 1;//第二層布局

    public TwoRecyclerViewAdapter(List<TheFirstBean> list) {
        for (int i=0;i<list.size();i++){
            firstBeanSparseArray.put(i,list.get(i));
        }
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //根據(jù)ViewType實(shí)例化布局
        switch (viewType){
            case TYPE_FIRST:
                return new FirstViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler,parent,false));
            case TYPE_SECOND:
                return new FirstViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler_detail,parent,false));
        }
        return new FirstViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler,parent,false));
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

    }

    @Override
    public int getItemCount() {
        return firstBeanSparseArray.size()+secondBeanSparseArray.size();
    }

    @Override
    public int getItemViewType(int position) {
        if (secondBeanSparseArray.get(position) != null){
            return TYPE_SECOND;
        }
        return TYPE_FIRST;
    }

    private class FirstViewHolder extends RecyclerView.ViewHolder{

        public FirstViewHolder(final View itemView) {
            super(itemView);
            //item點(diǎn)擊事件監(jiān)聽
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (firstBeanSparseArray.get(getLayoutPosition()).isExpand()){
                        //設(shè)置第二級(jí)布局是否展開的flag
                        firstBeanSparseArray.get(getLayoutPosition()).setExpand(false);
                        //獲取要移除的第二級(jí)布局個(gè)數(shù)
                        int addedSubNum = firstBeanSparseArray.get(getLayoutPosition()).getAddedSubNum();
                        //移除第二級(jí)布局
                        removeItems(getLayoutPosition(),addedSubNum);
                        notifyItemRangeRemoved(getLayoutPosition()+1,addedSubNum);
                    }else{
                        //設(shè)置第二級(jí)布局是否展開的flag
                        firstBeanSparseArray.get(getLayoutPosition()).setExpand(true);
                        //加載數(shù)據(jù)并獲取載入的第二級(jí)布局個(gè)數(shù)
                        List<TheSecondBean> list = new ArrayList<>();
                        for (int i =0;i<5;i++){
                            list.add(new TheSecondBean());
                        }
                        int addedSubNum = setEachFlows(getLayoutPosition(),list);
                        //添加第二級(jí)布局
                        firstBeanSparseArray.get(getLayoutPosition()).setAddedSubNum(addedSubNum);
                        notifyItemRangeInserted(getLayoutPosition()+1,addedSubNum);
                    }

                }
            });
        }
    }

    private class SecondViewHolder extends RecyclerView.ViewHolder{

        public SecondViewHolder(View itemView) {
            super(itemView);
        }
    }


    /**
     * 點(diǎn)擊展開時(shí)加載相應(yīng)數(shù)據(jù)
     * @param parentPosition
     * @param list
     * @return
     */
    public int setEachFlows(int parentPosition , List<TheSecondBean> list) {

        //更新position大于當(dāng)前點(diǎn)擊的position的第一級(jí)布局的item的position
        for (int i = getItemCount()-1 ; i > parentPosition ; i-- ){
            int index = firstBeanSparseArray.indexOfKey(i);
            if (index<0){
                continue;
            }
            TheFirstBean dailyFlow = firstBeanSparseArray.valueAt(index);
            firstBeanSparseArray.removeAt(index);
            firstBeanSparseArray.put(list.size()+i,dailyFlow);
        }
        //更新position大于當(dāng)前點(diǎn)擊的position的第二級(jí)布局的item的position
        for (int i = getItemCount()-1 ; i > parentPosition ; i-- ){
            int index = secondBeanSparseArray.indexOfKey(i);
            if (index<0){
                continue;
            }
            TheSecondBean eachFlow = secondBeanSparseArray.valueAt(index);
            secondBeanSparseArray.removeAt(index);
            secondBeanSparseArray.append(list.size()+i,eachFlow);
        }
        //把獲取到的數(shù)據(jù)根據(jù)相應(yīng)的position放入SparseArray中。
        for (int i = 0 ;i < list.size() ; i++ ){
            secondBeanSparseArray.put(parentPosition+i+1,list.get(i));
        }
        return list.size();
    }

    /**
     * 點(diǎn)擊折疊時(shí)移除相應(yīng)數(shù)據(jù)
     * @param clickPosition
     * @param addedSubNum
     */
    private void removeItems(int clickPosition,int addedSubNum){
        //更新position大于當(dāng)前點(diǎn)擊的position的第一級(jí)布局item的position
        SparseArray<TheFirstBean> temp = new SparseArray();
        for (int i = getItemCount()-1 ; i > clickPosition+addedSubNum ; i-- ){
            int index = firstBeanSparseArray.indexOfKey(i);
            if (index<0){
                continue;
            }
            TheFirstBean dailyFlow = firstBeanSparseArray.valueAt(index);
            firstBeanSparseArray.removeAt(index);
            temp.put(i-addedSubNum,dailyFlow);
        }
        for (int i=0;i<temp.size();i++ ){

            int key = temp.keyAt(i);
            firstBeanSparseArray.put(key,temp.get(key));
        }
        //更新position大于當(dāng)前點(diǎn)擊的position的第二級(jí)布局item的position
        SparseArray<TheSecondBean> temp2 = new SparseArray();
        for (int i = getItemCount()-1 ; i > clickPosition+addedSubNum ; i-- ){
            int index = secondBeanSparseArray.indexOfKey(i);
            if (index<0){
                continue;
            }
            TheSecondBean eachFlow = secondBeanSparseArray.valueAt(index);
            secondBeanSparseArray.removeAt(index);
            temp2.put(i-addedSubNum,eachFlow);
        }
        for (int i = 1; i <= addedSubNum; i++) {
            //移除被折疊的第二級(jí)布局?jǐn)?shù)據(jù)
            secondBeanSparseArray.remove(clickPosition+i);
        }
        for (int i=0;i<temp2.size();i++ ){

            int key = temp2.keyAt(i);
            secondBeanSparseArray.put(key,temp2.get(key));
        }
    }

}

以上。
希望我的文章對(duì)你能有所幫助。
我不能保證文中所有說法的百分百正確，但我能保證它們都是我的理解和感悟以及拒絕復(fù)制黏貼。
有什么意見、見解或疑惑，歡迎留言討論。