下拉列表

<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" >

    <EditText
        android:id="@+id/input"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="10dp"
        android:text="@string/hello_world" />

    <!-- 下啦三角图案 -->
    <ImageView 
        android:id="@+id/down_arrow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/down_arrow"
        android:layout_alignRight="@id/input"
        android:clickable="true"
        android:layout_marginTop="20dp" />
</RelativeLayout>

package com.example.testdemo;

import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.PopupWindow;
import android.widget.TextView;

public class MainActivity extends Activity {

    private EditText et_input;
    private ImageView downArrow;
    private List<String> msgList;
    private PopupWindow popWin;
    private ListView listView;

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

        et_input = (EditText) findViewById(R.id.input);
        downArrow = (ImageView) findViewById(R.id.down_arrow);
        msgList = new ArrayList<String>();

        for (int i = 0; i < 20; i++) {
            msgList.add("1000000000" + i);
        }

        initListView();

        downArrow.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                System.out.println("=======");
                // 定义 popupWindow
                popWin = new PopupWindow(MainActivity.this);
                // 设置宽度
                popWin.setWidth(et_input.getWidth());
                // 设置popWin 高度
                popWin.setHeight(200);
                // 为popWindow填充内容
                popWin.setContentView(listView);
                // 点击popWin 以处的区域，自动关闭 popWin
                popWin.setOutsideTouchable(true);
                // 设置 弹出窗口，显示的位置
                popWin.showAsDropDown(et_input, 0, 0);
            }
        });
    }

    private void initListView() {
        listView = new ListView(this);
        // 设置listView背景
        listView.setBackgroundResource(R.drawable.listview_background); 
        // 设置条目之间的分隔线为null
        listView.setDivider(null); 
        // 关闭
        listView.setVerticalScrollBarEnabled(false); 
        listView.setAdapter(new MyListAdapter());
    }

    private class MyListAdapter extends BaseAdapter {
        @Override
        public int getCount() {
            return msgList.size();
        }
        @Override
        public Object getItem(int position) {
            return 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(getApplicationContext(),
                        R.layout.list_item, null);
                holder = new ViewHolder();

                holder.delete = (ImageView) convertView
                        .findViewById(R.id.delete);
                holder.tv_msg = (TextView) convertView
                        .findViewById(R.id.tv_list_item);
                convertView.setTag(holder);
            } else {
                holder = (ViewHolder) convertView.getTag();
            }
            holder.tv_msg.setText(msgList.get(position));
            holder.delete.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    // 删除对应的条目
                    msgList.remove(position);
                    // 刷新listView
                    MyListAdapter.this.notifyDataSetChanged();
                }
            });
            convertView.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    // 设置输入框
                    et_input.setText(msgList.get(position));
                    popWin.dismiss();
                }
            });
            return convertView;
        }
    }

    private class ViewHolder {
        TextView tv_msg;
        ImageView delete;
    }

}