android - 对 performFiltering 的约束在第一个字符上返回 null

Question

我为 AutoCompleteTextView 编写了自定义过滤器。它工作正常，但是一件小事。 performFiltering 的约束在第一个字符上为空。这意味着只有当第二个字符被放入 AutoCompleteTextView 时，过滤过程才会开始。

这是过滤器的代码:

private Filter nameFilter = new Filter() {
    public String convertResultToString(Object resultValue) {
        String fullName = ((User)(resultValue)).facebookName; 
        return fullName;
    }

    @Override
    protected FilterResults performFiltering(CharSequence constraint) {
        if(constraint != null) {
            suggestions.clear();
            for (User friend : allFriends) {
                if(friend.facebookName.toLowerCase().contains(constraint.toString().toLowerCase())){
                    suggestions.add(friend);
                }
            }
            FilterResults filterResults = new FilterResults();
            filterResults.values = suggestions;
            filterResults.count = suggestions.size();
            return filterResults;
        } else {
            return new FilterResults();
        }
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
        ArrayList<User> filteredList = (ArrayList<User>) results.values;
        if(results != null && results.count > 0) {
            clear();
            for (User friend : filteredList) {
                add(friend);
            }
            notifyDataSetChanged();
        }

    }
};

谁能帮我解决这个问题，让过滤器从第一个字符开始过滤？

Answer 1

设置threshold到 1:

autoCompleteTextView.setThreshold(1)

Specifies the minimum number of characters the user has to type in the edit box before the drop down list is shown. When threshold is less than or equals 0, a threshold of 1 is applied.