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);
}
}
}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);
}/**
* 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;
}
}
}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);
}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;
}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();
}
}
}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;
}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座标等于中间-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座标
final int oldChoose = choose;
final OnTouchingLetterChangedListener listener = onTouchingLetterChangedListener;
final int c = (int) (y / getHeight() * b.length);// 点击y座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);
}
}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