可直接使用spinner控制元件實現。

先上效果圖

點選下拉按鈕時（其實是個imageView圖片）

佈局檔案

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

    tools:context=".MainActivity">


    <EditText
        android:id="@+id/et"
        android:layout_marginTop="30dp"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:paddingLeft="5dp"
        android:layout_width="match_parent"
        android:layout_height
 
="wrap_content"
        android:background="@drawable/et_normal"
        />

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="25dp"
        android:layout_marginRight="20dp"
        android:src
 
="@drawable/down_arrow"
        android:layout_alignParentRight="true"
        />
</RelativeLayout>

主程式

package com.example.administrator.spinnerdemo;

import android.graphics.drawable.ColorDrawable;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.PopupWindow;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener, AdapterView.OnItemClickListener {

    private EditText et;
    private ImageView iv;
    //模擬一個listView的資料
    List<String> mDatas;
    private Myadapter adapter;
    private PopupWindow popupWindow;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        initUI();
        initData();
    }



    private void initUI() {
        setContentView(R.layout.activity_main);

        et = (EditText) findViewById(R.id.et);
        iv = (ImageView) findViewById(R.id.iv);

        iv.setOnClickListener(this);
    }

    private void initData() {
        mDatas = new ArrayList<String>();

        for (int i = 0; i < 50; i++) {
            mDatas.add(10000+i+"");
        }
    }

    @Override
    public void onClick(View v) {
        if (v == iv){
            clickArrow();
        }
    }

    /**
     * 點選箭頭
     */
    private void clickArrow() {

        if (popupWindow == null){
            //彈出一個listView的下拉框
            ListView contentView = new ListView(this);

            contentView.setOnItemClickListener(this);

            adapter = new Myadapter();
            contentView.setAdapter(adapter);
            int width = et.getWidth();
            int height = 380;


            popupWindow = new PopupWindow(contentView,width,height);
            //設定獲取焦點，防止多次彈出，實現點一次彈出一次，再點一次收起
            popupWindow.setFocusable(true);
            //設定邊緣點選收起
            popupWindow.setOutsideTouchable(true);
            popupWindow.setBackgroundDrawable(new ColorDrawable());
        }


        //放在EditText下面
        popupWindow.showAsDropDown(et);
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        String name = mDatas.get(position);
        et.setText(name);
        popupWindow.dismiss();
    }

    private class Myadapter extends BaseAdapter{
        @Override
        public int getCount() {
            return mDatas.size();
        }

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

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

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder holder;

            if (convertView == null) {
                convertView = View.inflate(MainActivity.this,R.layout.item_list_view, null);

                holder = new ViewHolder();
                holder.text = (TextView) convertView.findViewById(R.id.tv_name);
                holder.icon = (ImageView) convertView.findViewById(R.id.iv_delete);

                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }

            holder.text.setText(mDatas.get(position));
            holder.icon.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mDatas.remove(position);
                    adapter.notifyDataSetChanged();
                }
            });

            return convertView;
        }
    }

    static class ViewHolder{
        TextView text;
        ImageView icon;
    }


}