（五）展示界面数据

数据源处理完毕后，需要显示在界面上

首先引入了这个比较实用的recycleview库

它支持recycleview的多布局

compile 'cc.solart:turbo-recyclerview-helper:1.0.3-beta'

然后自定义了一个侧边栏控件，主要参照下面这个控件改动的

GitHub - Solartisan/WaveSideBar

首先在Xml文件中用一个帧布局包裹这个侧边栏控件和recycleview

接下来便是适配器

因为有两种不同的item类型，所以使用了多布局的适配器，具体如下：

/**
 * Created by Administrator on 2017/7/6 0006.
 * 音乐列表适配器
 */

public class MusicListAdapter extends BaseTurboAdapter<Song, BaseViewHolder> {


    //构造方法
    public MusicListAdapter(Context context, List<Song> data) {
        super(context, data);
    }


    @Override
    protected int getDefItemViewType(int position) {
        Song song = getItem(position);
        return song.type;
    }

    @Override
    protected BaseViewHolder onCreateDefViewHolder(ViewGroup parent, int viewType) {
        /**
         * 1代表歌曲
         * 0代表首字母
         */
        if (viewType == 1)
            return new SongHolder(inflateItemView(R.layout.item_song, parent));
        else
            return new PinnedHolder(inflateItemView(R.layout.item_pinned_header, parent));
    }


    @Override
    protected void convert(final BaseViewHolder holder, final Song item) {

        if (holder instanceof SongHolder) {
            ((SongHolder) holder).song_name.setText(item.song);
            ((SongHolder) holder).singer_name.setText(item.singer);
            /**
             *  接口回调第四步 在onBindViewHolder方法内，实现回调
             */
            if (mOnItemClickListener != null) {
                //为ItemView设置监听器
                ((SongHolder) holder).item_song.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        mOnItemClickListener.onItemClick((SongHolder) holder, holder.getLayoutPosition() - getHeaderViewsCount(),item);
                    }
                });
            }
        } else {
            String letter = item.pys.substring(0, 1);
            ((PinnedHolder) holder).song_tip.setText(letter);
        }
    }

    public int getLetterPosition(String letter) {
        for (int i = 0; i < getData().size(); i++) {
            if (getData().get(i).type == 0 && getData().get(i).pys.equals(letter)) {
                return i;
            }
        }
        return -1;
    }


    /**
     * 歌曲控件绑定
     */
    public class SongHolder extends BaseViewHolder {

        TextView song_name;
        TextView singer_name;
        RelativeLayout item_song;

        public SongHolder(View view) {
            super(view);
            song_name = findViewById(R.id.song_name);
            singer_name = findViewById(R.id.singer_name);
            item_song = findViewById(R.id.item_song);

        }
    }


    /**
     * 首字母控件绑定
     */
    class PinnedHolder extends BaseViewHolder {

        TextView song_tip;

        public PinnedHolder(View view) {
            super(view);
            song_tip = findViewById(R.id.song_tip);
        }
    }


    //接口回调第二步 新建私有变量用于保存用户设置的监听器及其set方法
    private OnItemClickListener mOnItemClickListener;

    /**
     * 接口回调第一步 新建内部接口，用来做点击监听
     */
    public interface OnItemClickListener {
        void onItemClick(SongHolder view, int position,Song item);
    }

    //接口回调第三步 设置set方法
    public void setOnItemClickListener(OnItemClickListener mOnItemClickListener) {
        this.mOnItemClickListener = mOnItemClickListener;
    }
}

适配器完成后，回到音乐列表界面

Recycleview设置LayoutManager为线性方向

同时自定义了一个分割线用来设置列表字母标题

分割线的registerTypePinnedHeader方法中第一个参数输入的是字母标题的type类型

自定义分割线如下：

/**
 * Created by Administrator on 2017/7/6 0006.
 * 自定义的recycleview分割线
 */

public class PinnedHeaderDecoration extends RecyclerView.ItemDecoration {
    private int mHeaderPosition;
    private int mPinnedHeaderTop;

    private boolean mIsAdapterDataChanged;

    private Rect mClipBounds;
    private View mPinnedHeaderView;
    private RecyclerView.Adapter mAdapter;

    private final SparseArray<PinnedHeaderCreator> mTypePinnedHeaderFactories = new SparseArray<>();
    private final RecyclerView.AdapterDataObserver mAdapterDataObserver = new RecyclerView.AdapterDataObserver() {
        @Override
        public void onChanged() {
            mIsAdapterDataChanged = true;
        }
    };

    public PinnedHeaderDecoration() {
        this.mHeaderPosition = -1;
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        createPinnedHeader(parent);

        if (mPinnedHeaderView != null) {
            int headerEndAt = mPinnedHeaderView.getTop() + mPinnedHeaderView.getHeight();
            View v = parent.findChildViewUnder(c.getWidth() / 2, headerEndAt + 1);

            if (isPinnedView(parent, v)) {
                mPinnedHeaderTop = v.getTop() - mPinnedHeaderView.getHeight();
            } else {
                mPinnedHeaderTop = 0;
            }

            mClipBounds = c.getClipBounds();
            mClipBounds.top = mPinnedHeaderTop + mPinnedHeaderView.getHeight();
            c.clipRect(mClipBounds);
        }
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if (mPinnedHeaderView != null) {
            c.save();

            mClipBounds.top = 0;
            c.clipRect(mClipBounds, Region.Op.UNION);
            c.translate(0, mPinnedHeaderTop);
            mPinnedHeaderView.draw(c);

            c.restore();
        }
    }

    private void createPinnedHeader(RecyclerView parent) {
        updatePinnedHeader(parent);

        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager == null || layoutManager.getChildCount() <= 0) {
            return;
        }
        int firstVisiblePosition = ((RecyclerView.LayoutParams) layoutManager.getChildAt(0).getLayoutParams()).getViewAdapterPosition();
        int headerPosition = findPinnedHeaderPosition(parent, firstVisiblePosition);

        if (headerPosition >= 0 && mHeaderPosition != headerPosition) {
            mHeaderPosition = headerPosition;
            int viewType = mAdapter.getItemViewType(headerPosition);

            RecyclerView.ViewHolder pinnedViewHolder = mAdapter.createViewHolder(parent, viewType);
            mAdapter.bindViewHolder(pinnedViewHolder, headerPosition);
            mPinnedHeaderView = pinnedViewHolder.itemView;

            // read layout parameters
            ViewGroup.LayoutParams layoutParams = mPinnedHeaderView.getLayoutParams();
            if (layoutParams == null) {
                layoutParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
                mPinnedHeaderView.setLayoutParams(layoutParams);
            }

            int heightMode = View.MeasureSpec.getMode(layoutParams.height);
            int heightSize = View.MeasureSpec.getSize(layoutParams.height);

            if (heightMode == View.MeasureSpec.UNSPECIFIED) {
                heightMode = View.MeasureSpec.EXACTLY;
            }

            int maxHeight = parent.getHeight() - parent.getPaddingTop() - parent.getPaddingBottom();
            if (heightSize > maxHeight) {
                heightSize = maxHeight;
            }

            // measure & layout
            int ws = View.MeasureSpec.makeMeasureSpec(parent.getWidth() - parent.getPaddingLeft() - parent.getPaddingRight(), View.MeasureSpec.EXACTLY);
            int hs = View.MeasureSpec.makeMeasureSpec(heightSize, heightMode);
            mPinnedHeaderView.measure(ws, hs);
            mPinnedHeaderView.layout(0, 0, mPinnedHeaderView.getMeasuredWidth(), mPinnedHeaderView.getMeasuredHeight());
        }
    }

    private int findPinnedHeaderPosition(RecyclerView parent, int fromPosition) {
        if (fromPosition > mAdapter.getItemCount() || fromPosition < 0) {
            return -1;
        }

        for (int position = fromPosition; position >= 0; position--) {
            final int viewType = mAdapter.getItemViewType(position);
            if (isPinnedViewType(parent, position, viewType)) {
                return position;
            }
        }

        return -1;
    }

    private boolean isPinnedViewType(RecyclerView parent, int adapterPosition, int viewType) {
        PinnedHeaderCreator pinnedHeaderCreator =  mTypePinnedHeaderFactories.get(viewType);

        return pinnedHeaderCreator != null && pinnedHeaderCreator.create(parent, adapterPosition);
    }

    private boolean isPinnedView(RecyclerView parent, View v) {
        int position = parent.getChildAdapterPosition(v);
        if (position == RecyclerView.NO_POSITION) {
            return false;
        }

        return isPinnedViewType(parent, position, mAdapter.getItemViewType(position));
    }

    private void updatePinnedHeader(RecyclerView parent) {
        RecyclerView.Adapter adapter = parent.getAdapter();
        if (mAdapter != adapter || mIsAdapterDataChanged) {
            resetPinnedHeader();
            if (mAdapter != null) {
                mAdapter.unregisterAdapterDataObserver(mAdapterDataObserver);
            }

            mAdapter = adapter;
            if (mAdapter != null) {
                mAdapter.registerAdapterDataObserver(mAdapterDataObserver);
            }
        }
    }

    private void resetPinnedHeader() {
        mHeaderPosition = -1;
        mPinnedHeaderView = null;
    }

    public void registerTypePinnedHeader(int itemType, PinnedHeaderCreator pinnedHeaderCreator) {
        mTypePinnedHeaderFactories.put(itemType, pinnedHeaderCreator);
    }

    public interface PinnedHeaderCreator {
        boolean create(RecyclerView parent, int adapterPosition);
    }
}

侧边滑动栏调用下列方法即可实现定位

mSideBarView.setOnTouchLetterChangeListener(new WaveSideBarView.OnTouchLetterChangeListener() {

    @Override

    public void onLetterChange(String letter) {

        int pos = adapter.getLetterPosition(letter);

        if (pos != -1) {

            recycler_music.scrollToPosition(pos);

            mLayoutManager.scrollToPositionWithOffset(pos, 0);

        }

    }

})