searchEdittext.addTextChangedListener(new TextWatcher() {
  @Override
  public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
    // When user change the text
    mAdapter.getFilter().filter(cs);
  }
  
  @Override
  public void beforeTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
    //
  }
  
  @Override
  public void afterTextChanged(Editable arg0) {
    //
  }
});

public class ArrayAdapter<T> extends BaseAdapter implements Filterable {
  /**
   * Contains the list of objects that represent the data of this ArrayAdapter.
   * The content of this list is referred to as "the array" in the documentation.
   */
  private List<T> mObjects;
  
  /**
   * Lock used to modify the content of {@link #mObjects}. Any write operation
   * performed on the array should be synchronized on this lock. This lock is also
   * used by the filter (see {@link #getFilter()} to make a synchronized copy of
   * the original array of data.
   */
  private final Object mLock = new Object();
  
  // A copy of the original mObjects array, initialized from and then used instead as soon as
  // the mFilter ArrayFilter is used. mObjects will then only contain the filtered values.
  private ArrayList<T> mOriginalValues;
  private ArrayFilter mFilter;
  
  ...
  
  public Filter getFilter() {
    if (mFilter == null) {
      mFilter = new ArrayFilter();
    }
    return mFilter;
  }

  /**
   * <p>An array filter constrains the content of the array adapter with
   * a prefix. Each item that does not start with the supplied prefix
   * is removed from the list.</p>
   */
  private class ArrayFilter extends Filter {
    @Override
    protected FilterResults performFiltering(CharSequence prefix) {
      FilterResults results = new FilterResults();

      if (mOriginalValues == null) {
        synchronized (mLock) {
          mOriginalValues = new ArrayList<T>(mObjects);
        }
      }

      if (prefix == null || prefix.length() == 0) {
        ArrayList<T> list;
        synchronized (mLock) {
          list = new ArrayList<T>(mOriginalValues);
        }
        results.values = list;
        results.count = list.size();
      } else {
        String prefixString = prefix.toString().toLowerCase();

        ArrayList<T> values;
        synchronized (mLock) {
          values = new ArrayList<T>(mOriginalValues);
        }

        final int count = values.size();
        final ArrayList<T> newValues = new ArrayList<T>();

        for (int i = 0; i < count; i++) {
          final T value = values.get(i);
          final String valueText = value.toString().toLowerCase();

          // First match against the whole, non-splitted value
          if (valueText.startsWith(prefixString)) {
            newValues.add(value);
          } else {
            final String[] words = valueText.split(" ");
            final int wordCount = words.length;

            // Start at index 0, in case valueText starts with space(s)
            for (int k = 0; k < wordCount; k++) {
              if (words[k].startsWith(prefixString)) {
                newValues.add(value);
                break;
              }
            }
          }
        }

        results.values = newValues;
        results.count = newValues.size();
      }

      return results;
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
      //noinspection unchecked
      mObjects = (List<T>) results.values;
      if (results.count > 0) {
        notifyDataSetChanged();
      } else {
        notifyDataSetInvalidated();
      }
    }
  }
}

public class User {
  private int avatarResId;
  private String name;

  public User(int avatarResId, String name) {
    this.avatarResId = avatarResId;
    this.name = name;
  }

  public int getAvatarResId() {
    return avatarResId;
  }

  public void setAvatarResId(int avatarResId) {
    this.avatarResId = avatarResId;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
}

/**
   * Contains the list of objects that represent the data of this Adapter.
   * Adapter数据源
   */
  private List<User> mDatas;

 //过滤相关
  /**
   * This lock is also used by the filter
   * (see {@link #getFilter()} to make a synchronized copy of
   * the original array of data.
   * 过滤器上的锁可以同步复制原始数据。
   * 
   */
  private final Object mLock = new Object();

  // A copy of the original mObjects array, initialized from and then used instead as soon as
  // the mFilter ArrayFilter is used. mObjects will then only contain the filtered values.
  //对象数组的备份，当调用ArrayFilter的时候初始化和使用。此时，对象数组只包含已经过滤的数据。
  private ArrayList<User> mOriginalValues;
  private ArrayFilter mFilter;

 @Override
  public Filter getFilter() {
    if (mFilter == null) {
      mFilter = new ArrayFilter();
    }
    return mFilter;
  }

//执行过滤的方法
 protected FilterResults performFiltering(CharSequence prefix);

//得到过滤结果
 protected void publishResults(CharSequence prefix, FilterResults results);

 /**
   * 过滤数据的类
   */
  /**
   * <p>An array filter constrains the content of the array adapter with
   * a prefix. Each item that does not start with the supplied prefix
   * is removed from the list.</p>
   * <p/>
   * 一个带有首字母约束的数组过滤器，每一项不是以该首字母开头的都会被移除该list。
   */
  private class ArrayFilter extends Filter {
    //执行刷选
    @Override
    protected FilterResults performFiltering(CharSequence prefix) {
      FilterResults results = new FilterResults();//过滤的结果
      //原始数据备份为空时，上锁，同步复制原始数据
      if (mOriginalValues == null) {
        synchronized (mLock) {
          mOriginalValues = new ArrayList<>(mDatas);
        }
      }
      //当首字母为空时
      if (prefix == null || prefix.length() == 0) {
        ArrayList<User> list;
        synchronized (mLock) {//同步复制一个原始备份数据
          list = new ArrayList<>(mOriginalValues);
        }
        results.values = list;
        results.count = list.size();//此时返回的results就是原始的数据，不进行过滤
      } else {
        String prefixString = prefix.toString().toLowerCase();//转化为小写

        ArrayList<User> values;
        synchronized (mLock) {//同步复制一个原始备份数据
          values = new ArrayList<>(mOriginalValues);
        }
        final int count = values.size();
        final ArrayList<User> newValues = new ArrayList<>();

        for (int i = 0; i < count; i++) {
          final User value = values.get(i);//从List<User>中拿到User对象
//          final String valueText = value.toString().toLowerCase();
          final String valueText = value.getName().toString().toLowerCase();//User对象的name属性作为过滤的参数
          // First match against the whole, non-splitted value
          if (valueText.startsWith(prefixString) || valueText.indexOf(prefixString.toString()) != -1) {//第一个字符是否匹配
            newValues.add(value);//将这个item加入到数组对象中
          } else {//处理首字符是空格
            final String[] words = valueText.split(" ");
            final int wordCount = words.length;

            // Start at index 0, in case valueText starts with space(s)
            for (int k = 0; k < wordCount; k++) {
              if (words[k].startsWith(prefixString)) {//一旦找到匹配的就break，跳出for循环
                newValues.add(value);
                break;
              }
            }
          }
        }
        results.values = newValues;//此时的results就是过滤后的List<User>数组
        results.count = newValues.size();
      }
      return results;
    }

    //刷选结果
    @Override
    protected void publishResults(CharSequence prefix, FilterResults results) {
      //noinspection unchecked
      mDatas = (List<User>) results.values;//此时，Adapter数据源就是过滤后的Results
      if (results.count > 0) {
        notifyDataSetChanged();//这个相当于从mDatas中删除了一些数据，只是数据的变化，故使用notifyDataSetChanged()
      } else {
        /**
         * 数据容器变化 ----> notifyDataSetInValidated

         容器中的数据变化 ----> notifyDataSetChanged
         */
        notifyDataSetInvalidated();//当results.count<=0时，此时数据源就是重新new出来的，说明原始的数据源已经失效了
      }
    }
  }

//User对象的name属性作为过滤的参数
 final String valueText = value.getName().toString().toLowerCase();