通讯录的旁边有A-Z

1.定义一个类，继承View，三个有参构造方法，以及onDraw方法，用接口回调的方法设置点击事件。写一个dispatchTouchEvent方法，判断如果松开就隐藏，按下则显示。

2.在activity_main中定义Textview控件和自定义的类，并设置id,在MainActivity中找到控件，。

代码:

MainActivity:
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;
import android.widget.TextView;
import java.util.Collections;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private ListView mListview;
    private AddressAdapter adapter;
    private List<Address> addressList;
    private SlideBar mSlideBar;
    private TextView mTextletter;

    @Override
    protected voidonCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mListview = (ListView) findViewById(R.id.mListView);
        mSlideBar = (SlideBar) findViewById(R.id.sb_right);
        mTextletter = (TextView) findViewById(R.id.txt_letter);
        mSlideBar.setText(mTextletter);

        addressList = Address.getAddress();
        Collections.sort(addressList,newSort.AddressCompartor());
        adapter = new AddressAdapter(this,addressList);
        adapter.setIndex();
        mListview.setAdapter(adapter);

        mSlideBar.setListener(newSlideBar.OnTouchDownListener() {
            @Override
            public voidonTouch(String letter) {
                int index = adapter.getIndex(letter);
                if (index != -1) {
                    // listview设置当前的位置
                    mListview.setSelection(index);
                }
            }
        });
    }
}

address:
import java.util.ArrayList;
import java.util.List;

public class Address {
    private int id;
    private String name;

    public int getId() {
        return id;
    }

    public void setId(intid) {
        this.id= id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name= name;
    }
    public static List<Address> getAddress() {
        List<String> list = getAllMember();
        List<Address> addresses = new ArrayList<>();
        for (inti = 0; i < list.size(); i++) {
            Address address = new Address();
            address.setId(i);
            address.setName(list.get(i));
            addresses.add(address);
        }
        return addresses;
    }
    public static List<String> getAllMember() {
        List<String> addresses = new ArrayList<>();
        addresses.add("bdvs");
        addresses.add("马你不");
        addresses.add("王九");
        addresses.add("李广");
        addresses.add("李飞");
        addresses.add("张伟");
        addresses.add("马田");
        addresses.add("商具体");
        addresses.add("韩可以");
        addresses.add("张交易");
        addresses.add("韩吗");
        addresses.add("张近一");
        addresses.add("李进度");
        addresses.add("1512薛美女");
        addresses.add("杨今天");
        addresses.add("行核对");
        addresses.add("郭按时");
        addresses.add("郭方式");
        addresses.add("李百度");
        addresses.add("王过的");
        addresses.add("段更多");
        addresses.add("李和他");
        addresses.add("张舒服");
        addresses.add("刘方式");
        addresses.add("靳广东人");
        addresses.add("徐是");
        addresses.add("李黄飞");
        addresses.add("崔广办");
        addresses.add("宋答复");
        addresses.add("廉干部");
        addresses.add("张水电");
        addresses.add("绳可以");
        addresses.add("陈监狱");
        addresses.add("黄回调");
        addresses.add("李后台");
        addresses.add("王菊花");
        addresses.add("丛好热");
        addresses.add("刘三个");
        addresses.add("庞黄飞");
        addresses.add("杨嗨翻天");
        addresses.add("尹听过");
        return addresses;
    }
}

PinyinUtils:

import net.sourceforge.pinyin4j.PinyinHelper;
import net.sourceforge.pinyin4j.format.HanyuPinyinCaseType;
import net.sourceforge.pinyin4j.format.HanyuPinyinOutputFormat;
import net.sourceforge.pinyin4j.format.HanyuPinyinToneType;
import net.sourceforge.pinyin4j.format.HanyuPinyinVCharType;
import net.sourceforge.pinyin4j.format.exception.BadHanyuPinyinOutputFormatCombination;
public classPinyinUtils {

/** * 返回首字母，大写 */  public static String getFirstLetter(String str) {    if (TextUtils.isEmpty(str)) {        return "";    }    // 得到一个字符串的拼音的大写    String pinyinStr = getPinyin(str).toUpperCase();    // 取拼音字符串的第一个字母    char firstCahr = pinyinStr.charAt(0);    // 不是A-Z字母    if (firstCahr > 90 || firstCahr < 65) {        return "#";    }else{ // 代表是A-Z        return String.valueOf(firstCahr);    }}    /**     * 得到一个字符串的拼音读音     */    public static String getPinyin(String chineseStr) {        StringBuffer sb = new StringBuffer();        // 将汉字拆分成一个个的char        char[] chars = chineseStr.toCharArray();        // 遍历汉字的每一个char        for (int i = 0; i < chars.length; i++) {            try {                // 汉字的所有读音放在一个pinyins数组                String[] strings = PinyinHelper.toHanyuPinyinStringArray(chars[i], getDefaultFormat());                if (strings == null) {                    sb.append(chars[i]);                } else {                    sb.append(strings[0]);                }            } catch (BadHanyuPinyinOutputFormatCombination badHanyuPinyinOutputFormatCombination) {                badHanyuPinyinOutputFormatCombination.printStackTrace();            }        }        return sb.toString();    }    /**     * 设置默认的输出格式     */    public static HanyuPinyinOutputFormat getDefaultFormat() {        HanyuPinyinOutputFormat outputFormat = new HanyuPinyinOutputFormat();        //去除声调        outputFormat.setToneType(HanyuPinyinToneType.WITHOUT_TONE);        //小写        outputFormat.setCaseType(HanyuPinyinCaseType.LOWERCASE);        // 包含Unicode特殊字符        outputFormat.setVCharType(HanyuPinyinVCharType.WITH_U_UNICODE);        return outputFormat;    }}

Sort:

import java.util.Comparator;
public classSort {
    public static class AddressCompartorimplements Comparator<Address>{
        @Override public int compare(Address o1,Address o2) {
           String o1f = PinyinUtils.getFirstLetter(o1.getName());
           String o2f = PinyinUtils.getFirstLetter(o2.getName());
if (o1f.equals("#")) {
                  return 1;
             } else if (o2f.equals("#")) {
                  return -1;
             } else {
                 return o1f.compareTo(o2f);
            }
        }
    }
}

AddressAdapter:

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import java.util.List;
public classAddressAdapter extends BaseAdapter {
    private Context context;
    private List<Address> list;

    private Map<String, Integer> indexMap = new HashMap<>();    public AddressAdapter(Context context, List<Address> list) {        this.context = context;        this.list = list;    }
    public void setIndex() {      indexMap.clear();     for (int i = 0; i < list.size(); i++) {        // 遍历数据，得到首字母        String index = PinyinUtils.getFirstLetter(list.get(i).getName());        // 如果索引map中不包含这个字母，就添加进索引map，key是字母，value是第一次出现的位置        if (!indexMap.containsKey(index)) {            indexMap.put(index, i);          }      }  }    @Override    public int getCount() {        return list.size();    }    @Override    public Object getItem(int position) {        return list.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder holder;        if (convertView == null) {            holder = new ViewHolder();            convertView=View.inflate(context, R.layout.activity_address,null);
            holder.title= (TextView) convertView.findViewById(R.id.text_title);            holder.mTextName = (TextView) convertView.findViewById(R.id.mTextName);            convertView.setTag(holder);        } else {            holder = (ViewHolder) convertView.getTag();        }
      // 拿到当前条目     String str = addressList.get(position).getName();     // 取当前条目的首字母     String first = PinyinUtils.getFirstLetter(str);      if (indexMap.get(first) == position) {          holder.title.setVisibility(View.VISIBLE);          holder.title.setText(first);       } else {            holder.title.setVisibility(View.GONE);        }        holder.mTextName.setText(list.get(position).getName());        return convertView;    }    class ViewHolder {
        TextView title;        TextView mTextName;    }}

SlideBar:import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.support.annotation.Nullable;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.widget.TextView;import java.util.Date;public class SlideBar extends View {    private static final String TAG = "SlideBar";    private String[] letters = {            "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 OnTouchDownListener listener;    private TextView textView;    private int choose = -1;    private int oldChoose = -1;    public void setListener(OnTouchDownListener listener) {        this.listener = listener;    }    public SlideBar(Context context) {        super(context);    }    public SlideBar(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);    }    public SlideBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public void setText(TextView textView) {        this.textView = textView;    }    @Override    public boolean dispatchTouchEvent(MotionEvent event) {        int action = event.getAction();        // 手指触摸的纵坐标        float y = event.getY();        // 计算公式,字母的位置 = y*字母的总个数/总高度        int pos = (int) (y * letters.length / getHeight());        oldChoose = choose;        switch (action) {            case MotionEvent.ACTION_UP: // 手指抬起                // 把显示字母的textview隐藏                if (textView != null) {                    textView.setVisibility(View.INVISIBLE);                }                // 按下的位置设置成-1，未选中                choose = -1;                // 刷新，重绘                invalidate();                break;            default: // 手指按下和移动                // 在边界内，也就是在letters范围之内                if (pos >= 0 && pos < letters.length) {                    // 按下的时候显示 显示字母的textview，并且把字母设置成我们按下的位置的字母                    if (textView != null) {                        textView.setVisibility(VISIBLE);                        textView.setText(letters[pos]);                    }                    // 手指按下和移动的时候把当前选中的字母传出去                    if (listener != null) {                        listener.onTouch(letters[pos]);                    }                    // 改变当前选中的字母                    // 优化，只有当当前选中位置和上次选中的位置不同的时候才重绘                    if (oldChoose != pos){                        choose = pos;                        invalidate();                    }                }                break;        }        return true;    }    @Override    protected void onDraw(Canvas canvas) {        Log.i(TAG, "onDraw: " + new Date(System.currentTimeMillis()));        super.onDraw(canvas);        int width = getWidth();        int height = getHeight();        int singleHeight = height / letters.length;        Paint bgPaint = new Paint();        bgPaint.setColor(Color.parseColor("#44000000"));        bgPaint.setAntiAlias(true);        canvas.drawPaint(bgPaint);        bgPaint.reset();        for (int i = 0; i < letters.length; i++) {            Paint paint = new Paint();            paint.setColor(Color.parseColor("#FFFFFF"));            paint.setTextSize(30);            // 字符占的宽度            float f = paint.measureText(letters[i]);            float xPos = width / 2 - f / 2;            float yPos = singleHeight * (i + 1);            if (i == choose) {                paint.setColor(Color.parseColor("#FF0000"));                paint.setFakeBoldText(true);            }            canvas.drawText(letters[i], xPos, yPos, paint);            paint.reset();        }    }    interface OnTouchDownListener {        void onTouch(String letter);    }}