需求如题

话不多说 关门放码

《布局》

<androidx.appcompat.widget.AppCompatAutoCompleteTextView
            android:id="@+id/tv_str_service_name"
            android:completionThreshold="1"
            android:dropDownWidth="100dp"
            android:dropDownVerticalOffset="10dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@null"
            android:layout_marginEnd="16dp"
            android:hint="@string/str_service_name_hint"
            android:textColorHint="@color/color_979AA2"
            android:textColor="@color/color_979AA2"
            android:textSize="16sp"
            app:layout_constraintBottom_toBottomOf="@id/tv3"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="@id/tv3" />

关键属性
completionThreshold 代表输入几个字符匹配一次
dropDownWidth/Height 下拉框高度宽度
dropDownVerticalOffset 下拉框与输入框之间的垂直位移

《适配器》

public class AutoCompleteTextAdapter extends BaseAdapter implements Filterable {
    public static final int MAX_COUNT = 5;

    private ArrayFilter mFilter;//数据过滤器
    private List<HistorySearchEntity> mList;//传进来的数据
    private ArrayList<HistorySearchEntity> mFilteredData;//
    private Context context;//上下文
    public static List<HistorySearchEntity> newvalues;

    public AutoCompleteTextAdapter(List<HistorySearchEntity> mList, Context context) {
        this.mList = mList;
        this.context = context;
    }

    @Override
    public int getCount() {
        return mList == null ? 0 : mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view;
        ViewHolder viewHolder;
        if (convertView == null) {
            view = View.inflate(context, R.layout.item_pop_list, null);
            viewHolder = new ViewHolder();
            viewHolder.tv_city = view.findViewById(R.id.tv_item);
            view.setTag(viewHolder);
        } else {
            view = convertView;
            viewHolder = (ViewHolder) view.getTag();
        }

        HistorySearchEntity resultlist = mList.get(position);
        viewHolder.tv_city.setText(resultlist.getContent());

        return view;
    }

    static class ViewHolder {
        public TextView tv_city;

    }

    /**
     * 在后台线程执行，定义过滤算法
     * getFilter()方法会返回一个Filter对象，Filter是一个数据过滤器，其过滤操作是通过performFiltering()方法和publishResult()方法完成的。
     * performFiltering（）方法进行过滤操作，publishResult（）方法用于发表过滤操作结果。
     *
     * @return
     */
    @Override
    public Filter getFilter() {
        //创建过滤器的对象
        if (mFilter == null) {
            mFilter = new ArrayFilter();
        }
        return mFilter;
    }

    //过滤器类
    class ArrayFilter extends Filter {
        /**
         * @param constraint:用户在输入框中所输入的内容
         * @return
         */
        @Override//进行过滤操作
        protected FilterResults performFiltering(CharSequence constraint) {
            //使用过滤操作的结果
            FilterResults results = new FilterResults();

            if (mFilteredData == null) {
                //以一个集合初始化mFilteredData=new ArrayList<String>(mList);//mList(数组容量)为集合
                mFilteredData = new ArrayList<>(mList);
            }
            //如果没有输入内容，则不过滤
            if (constraint == null || constraint.length() == 0) {
                ArrayList<HistorySearchEntity> list = mFilteredData;
                results.values = list;
                results.count = list.size();
            } else {
                //过滤的条件
                String constraintString = constraint.toString().toLowerCase();
                //将传进来的全部数据赋值给filteredValues
                ArrayList<HistorySearchEntity> filteredValues = mFilteredData;
                int count = filteredValues.size();
                newvalues = new ArrayList<>(count);
                HistorySearchDaoUtil.search(constraintString, (ResultCallBack<List<HistorySearchEntity>>) list -> {
                    Log.i("damaris", "result: " + GsonUtils.toJson(list));
                    if (list.size() > MAX_COUNT) {
                        List<HistorySearchEntity> list1 = new ArrayList<>();
                        for (int i = 0; i < MAX_COUNT; i++) {
                            list1.add(list.get(i));
                        }
                        newvalues = list1;
                        results.values = list1;
                        results.count = list1.size();
                    } else {
                        newvalues = list;
                        results.values = list;
                        results.count = list.size();
                    }

                });

            }
            return results;
        }

        @Override//发表过滤操作结果
        protected void publishResults(CharSequence constraint, FilterResults results) {
            mList = (List<HistorySearchEntity>) results.values;
            if (results.count > 0) {
                //重绘当前可见区域
                notifyDataSetChanged();
            } else {
                //重绘控件，还原到初始状态
                notifyDataSetInvalidated();
            }
        }
    }

}

过滤条件自己定义。

《Room数据库查询语句》

@Query("SELECT * FROM TABLE_HISTORY_SEARCH_RECORD WHERE content LIKE '%' || :content || '%'")
    List<HistorySearchEntity> search(String content);

此处关于Room数据库不做过多讲解，只贴关键代码

《使用》

AppCompatAutoCompleteTextView tvStrServiceName = binding.tvStrServiceName;
        tvStrServiceName.setDropDownBackgroundResource(R.color.black);
        HistorySearchDaoUtil.getList((ResultCallBack<List<HistorySearchEntity>>) list -> {
            AutoCompleteTextAdapter adapter = new AutoCompleteTextAdapter(list, BindRoleDetailActivity.this);
            tvStrServiceName.setAdapter(adapter);
        });
        tvStrServiceName.setOnItemClickListener((parent, view, position, id) -> {
            //获取到过滤后的结果的集合
            List<HistorySearchEntity> results = AutoCompleteTextAdapter.newvalues;
            if (results != null && results.size() > 0) {
                HistorySearchEntity result = results.get(position);
                String s = result.getContent();
                tvStrServiceName.setText(s);
                //将光标放到文本最后
                tvStrServiceName.setSelection(tvStrServiceName.getText().length());
            } else {
                tvStrServiceName.setText("");
            }
        });

完事
AutoCompleteTextView文章：https://github.com/relish-wang/AutoCompleteTextViewSample