EditText_6

activity_edit_auto.xml 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="5dp" >

    <AutoCompleteTextView
        android:id="@+id/ac_text"
        style="@style/text_normal"
        android:padding="10dp"
        android:hint="请输入first或者second”"
        android:completionHint="相关词语"
        android:completionThreshold="1"
        android:dropDownHeight="wrap_content"
        android:dropDownHorizontalOffset="0dp"
        android:dropDownVerticalOffset="0dp"
        android:dropDownWidth="match_parent"
        android:textColor="#000000"
        android:textSize="17sp" />

</LinearLayout>

    <style name="text_normal">
        <item name="android:layout_width">match_parent</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:padding">3dp</item>
    </style>

item_dropdown.xml 

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:minHeight="40dp"
    android:gravity="center"
    android:textSize="17sp"
    android:textColor="#ff0000" />

MainActivity.java 

package com.example.third;

import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;

import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.EditText;

import android.widget.Toast;


public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    // 定义自动完成的提示文本数组
    private String[] hintArray = {"first", "first time", "first coding", "first salary", "second", "second mobile"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_edit_auto);
        // 从布局文件中获取名叫ac_text的自动完成编辑框
        AutoCompleteTextView ac_text = findViewById(R.id.ac_text);
        // 声明一个自动完成时下拉展示的数组适配器
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                this, R.layout.item_dropdown, hintArray);
        // 设置自动完成编辑框的数组适配器
        ac_text.setAdapter(adapter);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.btn_login) {
            Toast.makeText(this, "这个登录按钮啥事也没做", Toast.LENGTH_SHORT).show();
        }
    }
}