Pinyin4j的基本用法，以及给城市名称选择排序，侧边栏字母排序，内有Pinyin4j的下载链接，这是对我发表的上一篇文章进行修改以及更新bug，上一篇文章排序有点bug，现在将bug修改好了

1.需要下载Pinyin4j的jar包。下载地址为https://sourceforge.net/projects/pinyin4j/files/
下载后需要放到安卓项目目录下的libs文件夹。如下图片所示

然后还需要依赖这个jar包。不会导包的Android Studio导入jar包或aar包看这个链接。https://blog.youkuaiyun.com/qq_36570506/article/details/128019219
基本用法：
通常情况下，只需要用到其中的PinyinHelper类中的静态方法toHanyuPinyinStringArray就可以了，比如：
String[] pinyinArray =PinyinHelper.toHanyuPinyinStringArray(‘单’);
for(int i = 0; i < pinyinArray.length; ++i)
{
System.out.println(pinyinArray[i]);
}
就会输出：
dan1
chan2
shan4
这三种发音，后面的数字代表第几声。可以看到静态方法toHanyuPinyinStringArray返回的数据类型是一个String数组，它用来接收一个汉字的多个发音，如果toHanyuPinyinStringArray中的参数不是汉字，那么它会返回null。
2.上面的第一步，只是为了给城市名称转换成拼音输出，好为了城市名称按首字母排序，有了第一步的拼音，只需要将拼音的字符串截取第一位字母即可排序。排序见MainActivity类对象里面

import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import com.example.myapplication001.R.id;
import com.bumptech.glide.Glide;

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;

import java.text.Collator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

public class MainActivity extends AppCompatActivity  implements LetterSideBar.OnTouchLetterListener {
   

    private ImageView view;
    private TextView tv;

    private ListView listView;
    private LetterSideBar letterSideBar;
    private TextView textView;
    /**
     * 没有排序，旧的数据
     */
    private List<CityBean> mCities = new ArrayList();
    /**
     * 排序后的，新的数据
     */
    private List<CityBean> all_mCities = new ArrayList();
    private CityAdapter mAdapter;

    //----------------------------------------------------------------------------------------------
    //26个字母
    private List<CityBean> list_a = new ArrayList();
    private List<CityBean> list_b = new ArrayList();
    private List<CityBean> list_c = new ArrayList();
    private List<CityBean> list_d = new ArrayList();
    private List<CityBean> list_e = new ArrayList();
    private List<CityBean> list_f = new ArrayList();
    private List<CityBean> list_g = new ArrayList();
    private List<CityBean> list_h = new ArrayList();
    private List<CityBean> list_i = new ArrayList();
    private List<CityBean> list_j = new ArrayList();
    private List<CityBean> list_k = new ArrayList();
    private List<CityBean> list_l = new ArrayList();
    private List<CityBean> list_m = new ArrayList();
    private List<CityBean> list_n = new ArrayList();
    private List<CityBean> list_o = new ArrayList();
    private List<CityBean> list_p = new ArrayList();
    private List<CityBean> list_q = new ArrayList();
    private List<CityBean> list_r = new ArrayList();
    private List<CityBean> list_s = new ArrayList();
    private List<CityBean> list_t = new ArrayList();
    private List<CityBean> list_u = new