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ItemDecoration详解以及用ItemDecoration实现按字母排序列表

来源:IT165收集  发布日期:2016-12-19 20:31:50

首先看看实现的效果

可以看出要实现上面效果,有三个步骤:

1.汉字转化为拼音,并且根据首字母排序

2.用ItemDecoration实现字母行的显示

3.自定义实现右侧的按字母导航栏

当然重点讲讲ItemDecoration的实现。都知道RecyclerView本身都没有分割线,需要分割线都是在item中画一条线或者使用ItemDecoration来实现分割线。在RecyclerView中我们可以给每一个item都添加ItemDecoration,所以可以自定义ItemDecoration来实现各种我们所需要的效果。

ItemDecoration

ItemDecoration是RecyclerView内部的一个抽象类,要实现这个抽象类自然需要实现内部的抽象方法,除了deprecated的方法只有下面三个方法:

1.void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state)

这个方法是用来指定每一个的item对应decoration的大小区域,主要实现方式就是设置outRect的left、top、right、bottom,如果一个item不需要decoration把outRect的上下左右设置为0即可。盗用网上一张图看看outRect具体什么意思

2.void onDraw(Canvas c, RecyclerView parent, State state)

onDraw方法看名字大家都应该很熟悉,这个方法自然是用来画具体的ItemDecoration的,绘制的内容是显示在itemView的下层。下层什么意思,待会来看看。

3.void onDrawOver(Canvas c, RecyclerView parent, State state)

也是一个绘制的方法,不过是绘制在itemView的上层

以上三个方法的调用顺序也就是按照上面的排列的顺序来调用的。

首先来看看用ItemDecoration实现的分割线DividerItemDecoration

 

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};

    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;

    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;


    private Drawable mDivider;

    private int mOrientation;

    public DividerItemDecoration(Context context, int orientation) {
        //获取系统的divider
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
        setOrientation(orientation);
    }

    public void setOrientation(int orientation) {
        if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
            throw new IllegalArgumentException("invalid orientation");
        }
        mOrientation = orientation;
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDraw(c, parent, state);
        if (mOrientation == VERTICAL_LIST) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }
    }

    //画竖直分割线
    public void drawVertical(Canvas c, RecyclerView parent) {
        //左边缘距离RecyclerView左边的距离
        final int left = parent.getPaddingLeft();
        //右边缘距离RecyclerView右边边的距离
        final int right = parent.getWidth() - parent.getPaddingRight();

        final int childCount = parent.getChildCount();

        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom;
            //去掉最后一条的分割线
            if (i == childCount - 1) {//bottom和top相等,即高度为0 不显示
                bottom = top;
            } else {
                bottom = top + mDivider.getIntrinsicHeight();
            }
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    //画水平分割线
    public void drawHorizontal(Canvas c, RecyclerView parent) {
        final int top = parent.getPaddingTop();
        final int bottom = parent.getHeight() - parent.getPaddingBottom();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int left = child.getRight() + params.rightMargin;
            final int right = left + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        if (mOrientation == VERTICAL_LIST) {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}
主要实现了getItemOffsets和onDraw方法,因为这两个方法已经能满足了,自然不需要全部方法实现。在getItemOffsets方法中判断是竖直方向还是水平方向的分割线,竖直方向只需要在outRect的bottom加上分割线的宽度即可,当然水平分割线在右边加上就OK。在onDraw方法中具体的画出分割线,不知道大家有没有想过这里的分割线高度和outRect中设置的高度有什么关系,那么下面修改一下代码实验一下。

 

在上面onDraw画竖直分割线的方法中,把分割线高度加上80px,即:

 

mDivider.setBounds(left, top, right, bottom+80);

 

效果没变化?意思是onDraw里面画的区域大小不会超过outRect设置的大小吗?记得之前说过,onDraw方法绘制的内容是在itemView的下层的,会不会是被itemView遮挡而没有显示出来呢,那么下面我们把itemView的背景色改为透明,看看效果

android:background="@android:color/transparent"

 

这次看到了不同了吧,正是我们所猜想的那样。也就证明了onDraw方法显示的内容实在itemView的下层,同时它绘制的内容并不是不会超过outRect指定的区域,而outRect指定的区域也是实际分配给ItemDecoration的区域,在这个区域绘制才不会影响itemView,所以onDraw绘制的内容我们应该要保持和outRect给定的区域是相同的。

显示字母的ItemDecoration

现在来看看显示字母的ItemDecoration是怎么实现的。看上面的效果可以发现,最上面始终显示了一个ItemDecoration,上面说过onDrawOver方法绘制的内容是显示在最上层,所以用这个方法来绘制最上面再适合不过了。其他itemView显示字母的ItemDecoration也并不是采用onDraw方法绘制,而是用xml实现的,因为采用xml方式来实现可以更方便的来定制ItemDecoration的内容,也可以实现其中的点击事件。

在看ItemDecoration之前,先看看所用到的一个接口和RecyclerView的Adapter

 

public interface StickyHeaderAdapter<T extends RecyclerView.ViewHolder> {

    
    String getHeaderId(int position);

    
    T onCreateHeaderViewHolder(ViewGroup parent);

    
    void onBindHeaderViewHolder(T viewholder, int position);
}
这个接口里面有三个方法,第一个方法是获取headerId,因为在显示是不可能每一个item都要显示decoration,只有每种首字母第一个才显示,所用这里需要一个id来判断是否需要设置ItemDecoration。后面两个方法是仿照RecyclerView.Adapter的写的,因为我们采用ItemDecoration布局用xml实现,如果需要显示的ItemDecoration很多的话,每次都需要去用LayoutInflater去加载布局,显然不够优雅,所用用holder机制来实现复用。下面来看看我们的Adapter

 

 

/**
 * Created by lzy .
 * Date: 16/11/24
 */
public class MedicineAdapter extends RecyclerView.Adapter<MedicineAdapter.ViewHolder> implements
        StickyHeaderAdapter<MedicineAdapter.HeaderHolder> {
    private Context mContext;
    private List<MedicineBean> mDatas;
    private LayoutInflater mInflater;
    private int i;

    public MedicineAdapter(Context mContext, List<MedicineBean> mDatas) {
        this.mContext = mContext;
        this.mDatas = mDatas;
        mInflater = LayoutInflater.from(mContext);
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new ViewHolder(mInflater.inflate(R.layout.item_medicine, parent, false));
    }

    @Override
    public void onBindViewHolder(final ViewHolder holder, final int position) {
        final MedicineBean MedicineBean = mDatas.get(position);
        holder.tvName.setText(MedicineBean.getName());
    }

    @Override
    public int getItemCount() {
        return mDatas != null ? mDatas.size() : 0;
    }

    @Override
    public String getHeaderId(int position) {
        return mDatas.get(position).getLetter();
    }

    @Override//生成header的布局
    public HeaderHolder onCreateHeaderViewHolder(ViewGroup parent) {
        return new HeaderHolder(mInflater.inflate(R.layout.item_decoration, parent, false));
    }

    @Override//绑定header的数据
    public void onBindHeaderViewHolder(HeaderHolder viewholder, int position) {
        viewholder.header.setText(mDatas.get(position).getLetter());
    }

    /**
     * 根据分类的首字母获取其第一次出现该首字母的位置
     */
    public int getPositionForSection(String section) {
        for (int i = 0; i < mDatas.size(); i++) {
            String sortStr = mDatas.get(i).getLetter();
            if (sortStr.equals(section)) {
                return i;
            }
        }
        return -1;
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        TextView tvName;

        public ViewHolder(View itemView) {
            super(itemView);
            tvName = (TextView) itemView.findViewById(R.id.name);
        }
    }

    public static class HeaderHolder extends RecyclerView.ViewHolder {
        public TextView header;

        public HeaderHolder(View itemView) {
            super(itemView);
            header = (TextView) itemView;
        }
    }
}
可以看到这个Adapter实现了之前上面的接口,接口的实现方式和普通的Adapter的实现都类似在onCreateHeaderViewHolder中加载xml文件,在onBindHeaderViewHolder中加载数据,HeaderHolder也是一样的,headerId是采用的一个letter的,也就是每一条的首字母。下面看看ItemDecoration是怎么实现的。

 

getItemOffsets方法

首先看看第一个getItemOffsets方法的实现

 

 @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        //得到该item所在的位置
        int position = parent.getChildAdapterPosition(view);

        int headerHeight = 0;
        //在使用adapterPosition时最好的加上这个判断
        if (position != RecyclerView.NO_POSITION && hasHeader(position)) {
            //获取到ItemDecoration所需要的高度
            View header = getHeader(parent, position).itemView;
            headerHeight = header.getHeight();
        }
        outRect.set(0, headerHeight, 0, 0);
    }
很简单,就是判断如果这个item需要ItemDecoration就获取到header的高度,设置给outRect

 

判断是否需要header

判断是否需要header的方法,之前不是在Adapter里面写了getHeaderId的方法吗,这里就用到了,根据前两个headerId是否相同来判断是否需要设置ItemDecoration

 

private boolean hasHeader(int position) {
        if (position == 0) {//第一个位置必然有
            return true;
        }
        //判断和上一个的id不同则有header
        int previous = position - 1;
        return !mAdapter.getHeaderId(position).equals(mAdapter.getHeaderId(previous));
    }

获取Header的方法

 

private RecyclerView.ViewHolder getHeader(RecyclerView parent, int position) {
        //创建HeaderViewHolder
        MedicineAdapter.HeaderHolder holder = mAdapter.onCreateHeaderViewHolder(parent);
        final View header = holder.itemView;
        //绑定数据
        mAdapter.onBindHeaderViewHolder(holder, position);
        //测量View并且layout
        int widthSpec = View.MeasureSpec.makeMeasureSpec(parent.getWidth(), View.MeasureSpec.EXACTLY);
        int heightSpec = View.MeasureSpec.makeMeasureSpec(parent.getHeight(), View.MeasureSpec.UNSPECIFIED);
        //根据父View的MeasureSpec和子view自身的LayoutParams以及padding来获取子View的MeasureSpec
        int childWidth = ViewGroup.getChildMeasureSpec(widthSpec,
                parent.getPaddingLeft() + parent.getPaddingRight(), header.getLayoutParams().width);
        int childHeight = ViewGroup.getChildMeasureSpec(heightSpec,
                parent.getPaddingTop() + parent.getPaddingBottom(), header.getLayoutParams().height);
        //进行测量
        header.measure(childWidth, childHeight);
        //根据测量后的宽高放置位置
        header.layout(0, 0, header.getMeasuredWidth(), header.getMeasuredHeight());
        return holder;
    }
在这里面调用了之前Adapter实现接口里面的方法,创建了ViewHolder,绑定了数据。都知道自定义view需要实现onMeasure、onLayout、onDraw方法,所以在这里对它进行了测量和放置,而draw是在onDrawOver里面实现的。对这里熟悉的可以去看看相关的知识点。

 

onDrawOver方法

 

@Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        final int count = parent.getChildCount();

        for (int layoutPos = 0; layoutPos < count; layoutPos++) {
            final View child = parent.getChildAt(layoutPos);

            final int adapterPos = parent.getChildAdapterPosition(child);
            //只有在最上面一个item或者有header的item才绘制ItemDecoration
            if (adapterPos != RecyclerView.NO_POSITION && (layoutPos == 0 || hasHeader(adapterPos))) {
                View header = getHeader(parent, adapterPos).itemView;
                c.save();
                final int left = child.getLeft();
                final int top = getHeaderTop(parent, child, header, adapterPos, layoutPos);
                c.translate(left, top);
                header.setTranslationX(left);
                header.setTranslationY(top);
                header.draw(c);
                c.restore();
            }
        }
    }
这里就是一个循环,在需要Header的地方进行绘制,当然需要把画布移动到要绘制的位置,主要是确定它距离顶部的大小。

 

 

private int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos, int layoutPos) {
        int headerHeight = header.getHeight();
        int top = ((int) child.getY()) - headerHeight;
        if (layoutPos == 0) {//处理最上面两个ItemDecoration切换时
            final int count = parent.getChildCount();
            final String currentId = mAdapter.getHeaderId(adapterPos);
            for (int i = 1; i < count; i++) {
                int adapterPosHere = parent.getChildAdapterPosition(parent.getChildAt(i));
                if (adapterPosHere != RecyclerView.NO_POSITION) {
                    String nextId = mAdapter.getHeaderId(adapterPosHere);
                    if (!nextId.equals(currentId)) { //找到下一个不同类的view
                        final View next = parent.getChildAt(i);
                        //这里计算offset画个图会很清楚
                        final int offset = ((int) next.getY()) - (headerHeight + getHeader(parent, adapterPosHere).itemView.getHeight());
                        if (offset < 0) {//如果大于0的话,此时并没有切换
                            return offset;
                        } else {
                            break;
                        }
                    }
                }
            }
            //top不能小于0,否则最上面的ItemDecoration不会一直存在
            top = Math.max(0, top);
        }
        return top;
    }
这里的逻辑是这样的:

 

1.当此view不是最上面的显示的时候,header距离顶部直接就是此view距离顶部距离减去header的高度即可
2.当此view是最上面的view的时候,首先用for循环找到它下一个和它headerId不同的第一个view,利用找到的这个view和它本身来计算出它的header距离顶部的距离,当这个距离大于0时,代表此view的header还全部显示出来,这时直接用上面的方式获取这个距离,当这个距离小于0时就是我们所希望的。


OK完成,下面贴出ItemDecoration的所以代码

 

/**
 * Created by lzy on 2016/11/23.
 */
public class StickyItemDecoration extends RecyclerView.ItemDecoration {
    private static final String TAG = "lzy";
    private MedicineAdapter mAdapter;

    public StickyItemDecoration(MedicineAdapter mAdapter) {
        super();
        this.mAdapter = mAdapter;
    }

    //最后调用 绘制顶部固定的header
    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        final int count = parent.getChildCount();

        for (int layoutPos = 0; layoutPos < count; layoutPos++) {
            final View child = parent.getChildAt(layoutPos);

            final int adapterPos = parent.getChildAdapterPosition(child);
            //只有在最上面一个item或者有header的item才绘制ItemDecoration
            if (adapterPos != RecyclerView.NO_POSITION && (layoutPos == 0 || hasHeader(adapterPos))) {
                View header = getHeader(parent, adapterPos).itemView;
                c.save();
                final int left = child.getLeft();
                final int top = getHeaderTop(parent, child, header, adapterPos, layoutPos);
                c.translate(left, top);
                header.setTranslationX(left);
                header.setTranslationY(top);
                header.draw(c);
                c.restore();
            }
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        //得到该item所在的位置
        int position = parent.getChildAdapterPosition(view);

        int headerHeight = 0;
        //在使用adapterPosition时最好的加上这个判断
        if (position != RecyclerView.NO_POSITION && hasHeader(position)) {
            //获取到ItemDecoration所需要的高度
            View header = getHeader(parent, position).itemView;
            headerHeight = header.getHeight();
        }
        outRect.set(0, headerHeight, 0, 0);
    }

    /**
     * 判断是否有header
     *
     * @param position
     * @return
     */
    private boolean hasHeader(int position) {
        if (position == 0) {//第一个位置必然有
            return true;
        }
        //判断和上一个的id不同则有header
        int previous = position - 1;
        return !mAdapter.getHeaderId(position).equals(mAdapter.getHeaderId(previous));
    }

    /**
     * 获得自定义的Header
     *
     * @param parent
     * @param position
     * @return
     */
    private RecyclerView.ViewHolder getHeader(RecyclerView parent, int position) {
        //创建HeaderViewHolder
        MedicineAdapter.HeaderHolder holder = mAdapter.onCreateHeaderViewHolder(parent);
        final View header = holder.itemView;
        //绑定数据
        mAdapter.onBindHeaderViewHolder(holder, position);
        //测量View并且layout
        int widthSpec = View.MeasureSpec.makeMeasureSpec(parent.getWidth(), View.MeasureSpec.EXACTLY);
        int heightSpec = View.MeasureSpec.makeMeasureSpec(parent.getHeight(), View.MeasureSpec.UNSPECIFIED);
        //根据父View的MeasureSpec和子view自身的LayoutParams以及padding来获取子View的MeasureSpec
        int childWidth = ViewGroup.getChildMeasureSpec(widthSpec,
                parent.getPaddingLeft() + parent.getPaddingRight(), header.getLayoutParams().width);
        int childHeight = ViewGroup.getChildMeasureSpec(heightSpec,
                parent.getPaddingTop() + parent.getPaddingBottom(), header.getLayoutParams().height);
        //进行测量
        header.measure(childWidth, childHeight);
        //根据测量后的宽高放置位置
        header.layout(0, 0, header.getMeasuredWidth(), header.getMeasuredHeight());
        return holder;
    }

    /**
     * 计算距离顶部的高度
     *
     * @param parent
     * @param child
     * @param header
     * @param adapterPos
     * @param layoutPos
     * @return
     */
    private int getHeaderTop(RecyclerView parent, View child, View header, int adapterPos, int layoutPos) {
        int headerHeight = header.getHeight();
       int top = ((int) child.getY()) - headerHeight;
        if (layoutPos == 0) {//处理最上面两个ItemDecoration切换时
            final int count = parent.getChildCount();
            final String currentId = mAdapter.getHeaderId(adapterPos);
            for (int i = 1; i < count; i++) {
                int adapterPosHere = parent.getChildAdapterPosition(parent.getChildAt(i));
                if (adapterPosHere != RecyclerView.NO_POSITION) {
                    String nextId = mAdapter.getHeaderId(adapterPosHere);
                    //找到下一个不同类的view
                    if (!nextId.equals(currentId)) {
                        final View next = parent.getChildAt(i);
                        //这里计算offset画个图会很清楚
                        final int offset = ((int) next.getY()) - (headerHeight + getHeader(parent, adapterPosHere).itemView.getHeight());
                        if (offset < 0) {//如果大于0的话,此时并没有切换
                            return offset;
                        } else {
                            break;
                        }
                    }
                }
            }
            //top不能小于0,否则最上面的ItemDecoration不会一直存在
            top = Math.max(0, top);
        }
        return top;
    }
}

汉字转拼音

通过一个三方的类库pinyin4j来实现,这里就是调用方法PinyinHelper.toHanyuPinyinStringArray获取一个汉字的拼音,然后得到第一个英文字母并转化为大写

 

 private List<MedicineBean> filledData(String[] data) {
        List<MedicineBean> mSortList = new ArrayList<MedicineBean>();

        for (int i = 0; i < data.length; i++) {
            MedicineBean medicineBean = new MedicineBean();
            medicineBean.setName(data[i]);
            //汉字转换成拼音
            String[] pinyin = PinyinHelper.toHanyuPinyinStringArray(data[i].toCharArray()[0]);
            String sortString = pinyin[0].substring(0, 1).toUpperCase();
            // 正则表达式,判断首字母是否是英文字母
            if (sortString.matches("[A-Z]")) {
                medicineBean.setLetter(sortString.toUpperCase());
            } else {
                medicineBean.setLetter("#");
            }

            mSortList.add(medicineBean);
        }
        return mSortList;

    }


右边的字母导航栏

 

public class SideBar extends View {
    // 触摸事件
    private OnTouchingLetterChangedListener onTouchingLetterChangedListener;
    // 26个字母
    public static String[] b = {"A", "B", "C", "D", "E", "F", "G", "H", "I",
            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
            "W", "X", "Y", "Z", "#"};
    private int choose = -1;// 选中
    private Paint paint = new Paint();

    private TextView mTextDialog;

    public void setTextView(TextView mTextDialog) {
        this.mTextDialog = mTextDialog;
    }

    public SideBar(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public SideBar(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public SideBar(Context context) {
        super(context);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // 获取焦点改变背景颜色.
        int height = getHeight();// 获取对应高度
        int width = getWidth(); // 获取对应宽度
        int singleHeight = height / b.length;// 获取每一个字母的高度

        for (int i = 0; i < b.length; i++) {
            paint.setColor(Color.rgb(33, 65, 98));
            // paint.setColor(Color.WHITE);
            paint.setTypeface(Typeface.DEFAULT_BOLD);
            paint.setAntiAlias(true);
            paint.setTextSize(20);
            // 选中的状态
            if (i == choose) {
                paint.setColor(Color.parseColor("#3399ff"));
                paint.setFakeBoldText(true);
            }
            // x坐标等于中间-字符串宽度的一半.
            float xPos = width / 2 - paint.measureText(b[i]) / 2;
            float yPos = singleHeight * i + singleHeight;
            canvas.drawText(b[i], xPos, yPos, paint);
            paint.reset();// 重置画笔
        }

    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        final int action = event.getAction();
        final float y = event.getY();// 点击y坐标
        final int oldChoose = choose;
        final OnTouchingLetterChangedListener listener = onTouchingLetterChangedListener;
        final int c = (int) (y / getHeight() * b.length);// 点击y坐标所占总高度的比例*b数组的长度就等于点击b中的个数.

        switch (action) {
            case MotionEvent.ACTION_UP:
                setBackgroundDrawable(new ColorDrawable(0x00000000));
                choose = -1;//
                invalidate();
                if (mTextDialog != null) {
                    mTextDialog.setVisibility(View.INVISIBLE);
                }
                break;
            default:
                setBackgroundColor(Color.parseColor("#808080"));
                if (oldChoose != c) {
                    if (c >= 0 && c < b.length) {
                        if (listener != null) {
                            listener.onTouchingLetterChanged(b[c]);
                        }
                        if (mTextDialog != null) {
                            mTextDialog.setText(b[c]);
                            mTextDialog.setVisibility(View.VISIBLE);
                        }
                        choose = c;
                        invalidate();
                    }
                }

                break;
        }
        return true;
    }

    /**
     * 向外公开的方法
     *
     * @param onTouchingLetterChangedListener
     */
    public void setOnTouchingLetterChangedListener(
            OnTouchingLetterChangedListener onTouchingLetterChangedListener) {
        this.onTouchingLetterChangedListener = onTouchingLetterChangedListener;
    }

    /**
     * 接口
     *
     * @author coder
     */
    public interface OnTouchingLetterChangedListener {
        void onTouchingLetterChanged(String s);
    }

}
这是在网上找的一个类,相信大家都能看懂,就不多说了,最后贴出MainActivity

 

 

public class MainActivity extends AppCompatActivity {
    private String[] mData = {"阿魏八味丸", "阿昔洛韦眼膏", "艾司洛尔", "安吖啶注射液", "阿达帕林", "参茸追风酒", "草乌", "石斛夜光丸",
            "骨质增生片", "乌鸡白凤丸", "人参益母丸", "补脾益肠丸", "丹参片", "小金丸", "妇宁康", "糖脉康", "菲伯瑞", "乙肝解毒片", "脑血栓片"};
    private static final String TAG = "lzy";
    private RecyclerView mRecyclerView;
    private SideBar sideBar;
    private StickyItemDecoration mDecoration;
    private PinyinComparator pinyinComparator;
    private MedicineAdapter medicineAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRecyclerView = (RecyclerView) findViewById(R.id.rv);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        //按照字母排序
        pinyinComparator = new PinyinComparator();

        List<MedicineBean> data = filledData(mData);
        Collections.sort(data, pinyinComparator);

        medicineAdapter = new MedicineAdapter(this, data);
        mRecyclerView.setAdapter(medicineAdapter);
        mDecoration = new StickyItemDecoration(medicineAdapter);
        mRecyclerView.addItemDecoration(mDecoration);
        //添加分割线
        mRecyclerView.addItemDecoration(new DividerItemDecoration(MainActivity.this, DividerItemDecoration.VERTICAL_LIST));

        sideBar = (SideBar) findViewById(R.id.sideBar);
        sideBar.setTextView((TextView) findViewById(R.id.dialog));
        //设置右侧触摸监听
        sideBar.setOnTouchingLetterChangedListener(new SideBar.OnTouchingLetterChangedListener() {

            @Override
            public void onTouchingLetterChanged(String s) {
                //该字母首次出现的位置
                int position = medicineAdapter.getPositionForSection(s);
                if (position != -1) {
                    mRecyclerView.scrollToPosition(position);
                }

            }
        });

    }

    /**
     * 填充数据
     *
     * @param data
     * @return
     */
    private List<MedicineBean> filledData(String[] data) {
        List<MedicineBean> mSortList = new ArrayList<MedicineBean>();

        for (int i = 0; i < data.length; i++) {
            MedicineBean medicineBean = new MedicineBean();
            medicineBean.setName(data[i]);
            //汉字转换成拼音
            String[] pinyin = PinyinHelper.toHanyuPinyinStringArray(data[i].toCharArray()[0]);
            String sortString = pinyin[0].substring(0, 1).toUpperCase();
            // 正则表达式,判断首字母是否是英文字母
            if (sortString.matches("[A-Z]")) {
                medicineBean.setLetter(sortString.toUpperCase());
            } else {
                medicineBean.setLetter("#");
            }

            mSortList.add(medicineBean);
        }
        return mSortList;

    }
}

最后贴出源码的下载地址:http://download.csdn.net/detail/lylodyf/9695270

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Tag标签: 字母  
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