先看张效果图
device-2018-06-20-095811.gif
列表是用RecyclerView，demo中RecyclerView都是封装好的，小编是直接拿过来用的，至于怎么封装RecyclerView，绘制RecyclerView的分割线等等，有个半年经验左右应该是会封装的，至于不会，那就研究下我的代码是怎么封装的。哈哈！
具体思路：
1、对汉字进行A_Z排序 2、绘制字母A-Z索引LetterSideBarView 3、触摸响应手指的touch事件，需要考虑View的事件分发 4、绘制RecyclerView的分割线
LetterSideBarView
public class LetterSideBarView extends View {private Context mContext;//画笔private Paint mPaint;private String[] mLetters = {"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"};//手指当前触摸的字母private String mTouchLetter;//手指是否触摸private boolean mCurrentIsTouch;// 设置触摸监听private SideBarTouchListener mTouchListener;public LetterSideBarView(Context context) { this(context, null);
}public LetterSideBarView(Context context, @Nullable AttributeSet attrs) { this(context, attrs, 0);
}public LetterSideBarView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); this.mContext = context;
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setTextSize(DensityUtil.sp2px(this.getContext(), 14));
mPaint.setColor(Color.BLACK);
}@Overrideprotected void onDraw(Canvas canvas) { super.onDraw(canvas); //每一个字母的高度
float singleHeight = ( float ) getHeight() / mLetters.length; //不断循环把绘制字母
for (int i = 0; i < mLetters.length; i++) {
String letter = mLetters[i]; //获取字体的宽度
Rect rect = new Rect();
mPaint.getTextBounds(letter, 0, letter.length(), rect); float measureTextWidth = rect.width(); //获取内容的宽度
int contentWidth = getWidth() - getPaddingLeft() - getPaddingRight(); float x = getPaddingLeft() + (contentWidth - measureTextWidth) / 2; //计算基线位置
Paint.FontMetrics fontMetrics = mPaint.getFontMetrics(); float baseLine = singleHeight / 2 + (singleHeight * i) +
(fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom; //画字母，后面onTouch的时候需要处理高亮
if (mLetters[i].equals(mTouchLetter) && mCurrentIsTouch) {
mPaint.setTextSize(DensityUtil.sp2px(mContext, 18));
mPaint.setColor(Color.RED);
canvas.drawText(letter, x, baseLine, mPaint);
} else {
mPaint.setTextSize(DensityUtil.sp2px(mContext, 14));
mPaint.setColor(Color.BLACK);
canvas.drawText(letter, x, baseLine, mPaint);
}
}
}@Overridepublic boolean onTouchEvent(MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: case MotionEvent.ACTION_MOVE: //计算出当前触摸的字母，获取当前的位置
float currentMoveY = ( int ) event.getY(); int itemHeight = (getHeight() - getPaddingTop() - getPaddingBottom()) / mLetters.length; //当前的位置=currentMoveY/字母的高度
int currentPosition = ( int ) currentMoveY / itemHeight; if (currentPosition < 0) {
currentPosition = 0;
} if (currentPosition > mLetters.length - 1) {
currentPosition = mLetters.length - 1;
}
mTouchLetter = mLetters[currentPosition];
mCurrentIsTouch = true; if (mTouchListener != null) {
mTouchListener.onTouch(mTouchLetter, true);
} break; case MotionEvent.ACTION_UP:
mCurrentIsTouch = false; if (mTouchListener != null) {
mTouchListener.onTouch(mTouchLetter, false);
} break;
}
invalidate(); return true;
}public void setOnSideBarTouchListener(SideBarTouchListener touchListener) { this.mTouchListener = touchListener;
}计算出每个字母的基线baseLine，怎么计算呢？
5437668-8051a93a8a68dd67.png
top line: 文字可绘制区域最顶部的线；
ascent line: 系统推荐的，文字可绘制区域顶部的线；
baseline: 文字绘制的基线（在四线格上书写英文字母时的第三条线）；
descent line: 系统推荐的，文字可绘制区域底部的线；
bottom line: 文字可绘制区域最底部的线。
baseline是基线，baseline以上是负值，baseline以下是正值，因此ascent和top都是负值，descent和bottom都是正值。
//计算基线位置 Paint.FontMetrics fontMetrics = mPaint.getFontMetrics(); float baseLine = singleHeight / 2 + (singleHeight * i) +(fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
说下View的事件分发，需要执行ACTION_MOVE事件，ACTION_DOWN事件需要返回true消费这个事件，才能往下执行ACTION_MOVE事件。
MainActivity
public class MainActivity extends AppCompatActivity {private RecyclerView mRv;private LetterSideBarView mLetterSideBarView;private TextView mIndexTv;private List<Person> mList;private Handler mHandler = new Handler();private boolean isScale = false;@Overrideprotected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRv = findViewById(R.id.rv);
mLetterSideBarView = findViewById(R.id.letterSideBarView);
mIndexTv = findViewById(R.id.indexTv);
initRv();
mLetterSideBarView.setOnSideBarTouchListener(new SideBarTouchListener() { @Override
public void onTouch(String letter, boolean isTouch) { for (int i = 0; i < mList.size(); i++) { if (letter.equals(mList.get(i).getPinyin().charAt(0) + "")) {
mRv.scrollToPosition(i); break;
}
}
showCurrentIndex(letter);
}
});
}private void showCurrentIndex(String letter) {
mIndexTv.setText(letter); if (!isScale) {
isScale = true;
ViewCompat.animate(mIndexTv)
.scaleX(1f)
.setInterpolator(new OvershootInterpolator())
.setDuration(380)
.start();
ViewCompat.animate(mIndexTv)
.scaleY(1f)
.setInterpolator(new OvershootInterpolator())
.setDuration(380)
.start();
}
mHandler.removeCallbacksAndMessages(null); // 延时隐藏
mHandler.postDelayed(new Runnable() { @Override
public void run() {
ViewCompat.animate(mIndexTv)
.scaleX(0f)
.setDuration(380)
.start();
ViewCompat.animate(mIndexTv)
.scaleY(0f)
.setDuration(380)
.start();
isScale = false;
}
}, 380);
}private void initRv() {
mList = new ArrayList<>(); for (int i = 0; i < DataUtil.testData3.length; i++) {
Person person = new Person(DataUtil.testData3[i]);
mList.add(person);
} //排序
Collections.sort(mList);
PersonAdapter adapter = new PersonAdapter(this, mList, R.layout.person_recycler_item);
mRv.setAdapter(adapter);
mRv.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
//添加分割线
mRv.addItemDecoration(new DefaultItemDecoration(this, R.drawable.default_item));
}private class PersonAdapter extends CommonRecycleAdapter<Person> { public PersonAdapter(Context context, List<Person> mData, int layoutId) { super(context, mData, layoutId);
} @Override
protected void convert(CommonViewHolder holder, Person person, int position) {
String currentWord = person.getPinyin().charAt(0) + ""; if (position > 0) {
String lastWord = mList.get(position - 1).getPinyin().charAt(0) + ""; //拿当前的首字母和上一个首字母比较,与首字母相同，需要隐藏当前item的索引
holder.setVisibility(R.id.indexTv, currentWord.equals(lastWord) ? View.GONE : View.VISIBLE);
} else {
holder.setVisibility(R.id.indexTv, View.VISIBLE);
}
holder.setText(R.id.indexTv, currentWord);
holder.setText(R.id.userNameTv, person.getName());
}
}
}MainActivity大家看代码吧，都是些基础代码。主要是这个：拿当前的首字母和上一个首字母比较,与首字母相同，需要隐藏当前item上面索引。