activity_main:


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 tools:context="com.example.my_autocompletetextview.MainActivity">


 <AutoCompleteTextView
     android:id="@+id/autocomplete"
     android:completionThreshold="1"
     android:layout_width="match_parent"
     android:layout_height="wrap_content" />
 <!--<TextView-->
     <!--android:layout_width="wrap_content"-->
     <!--android:layout_height="wrap_content"-->
     <!--android:text="Hello World!"-->
     <!--app:layout_constraintBottom_toBottomOf="parent"-->
     <!--app:layout_constraintLeft_toLeftOf="parent"-->
     <!--app:layout_constraintRight_toRightOf="parent"-->
     <!--app:layout_constraintTop_toTopOf="parent" />-->

</LinearLayout>

item.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:src="@mipmap/ic_launcher"
        android:layout_width="30dp"
        android:layout_height="30dp" />
    <TextView
        android:id="@+id/text"
        android:textSize="20sp"
        android:text="hah"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

package com.example.my_autocompletetextview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.AutoCompleteTextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //1.准备数据源
        final String string[] = {"北京","上海","广州","1235","hello"};
        //2.准备适配器
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                MainActivity.this,     //
                R.layout.item,                 //显示的布局
                R.id.text,                     //显示的字符串
                string);                       //数据源
        //3.让控件和适配器进行关联
        AutoCompleteTextView autoCompleteTextView = findViewById(R.id.autocomplete);
        autoCompleteTextView.setAdapter(adapter);

        //当点击了某一列响应
        autoCompleteTextView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Toast.makeText(MainActivity.this,string[i],Toast.LENGTH_LONG).show();
            }
        });
    }

}

效果：(输出代码中具有的字符串的时候,会自动显示出来!)

image.png