Android下拉菜单效果

一、效果图

二、主要技术点：

　　1.PopupWindow的使用

　　2.ListView的使用

三、示例代码

　　1.布局文件：activity_main.xml

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/et"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:inputType="text" />

    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@id/et"
        android:src="@drawable/down_arrow" />

</RelativeLayout>

　　2.ListView的布局文件：list_item.xml

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

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/user" />

    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center"
        android:text="内容" 
        android:id="@+id/tv_listitem_content"/>

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/delete" 
        android:id="@+id/iv_listitem_delete"/>

</LinearLayout>

　　3.主界面MainActivity.java

package com.gnnuit.dropdownlist;

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

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;
import android.app.Activity;

public class MainActivity extends Activity {
    private ImageView iv;
    private PopupWindow popupWindow;
    private ListView lv;
    private EditText et;

    private List<String> strs = new ArrayList<String>();
    private MyAdapter adapter;

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

        initListView();// 初始化ListView

        et = (EditText) findViewById(R.id.et);
        iv = (ImageView) findViewById(R.id.iv);
        iv.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                if (popupWindow == null) {
                    popupWindow = new PopupWindow(MainActivity.this);
                    popupWindow.setContentView(lv);
                    // PopupWindow必须设置高度和宽度
                    popupWindow.setWidth(et.getWidth()); // 设置宽度
                    popupWindow.setHeight(200); // 设置popWin 高度
                    popupWindow.showAsDropDown(et, 0, 0);
                    popupWindow.setOutsideTouchable(true);// 设置后点击其他位置PopupWindow将消失
                } else if (popupWindow != null && popupWindow.isShowing()) {
                    popupWindow.dismiss();
                } else {
                    popupWindow.showAsDropDown(et);
                }
            }
        });
    }

    /**
     * 初始化ListView
     */
    private void initListView() {
        for (int i = 0; i < 10; i++) {
            strs.add("第" + i + "条记录");
        }
        lv = new ListView(this);
        if (adapter == null) {
            adapter = new MyAdapter();
            lv.setAdapter(adapter);
        } else {
            adapter.notifyDataSetChanged();
        }
        lv.setBackgroundResource(R.drawable.listview_background);
        lv.setDividerHeight(2);
        lv.setVerticalScrollBarEnabled(false);
    }

    private class MyAdapter extends BaseAdapter {

        @Override
        public int getCount() {
            return strs.size();
        }

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

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

        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            View view;
            ViewHolder holder;
            if (convertView == null) {
                view = View.inflate(MainActivity.this, R.layout.list_item, null);
                holder = new ViewHolder();
                holder.iv = (ImageView) view.findViewById(R.id.iv_listitem_delete);
                holder.tv = (TextView) view.findViewById(R.id.tv_listitem_content);
                view.setTag(holder);
            } else {
                view = convertView;
                holder = (ViewHolder) view.getTag();
            }
            holder.tv.setText(strs.get(position));
            holder.tv.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    et.setText(strs.get(position));
                    popupWindow.dismiss();
                }
            });
            holder.iv.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // 从List中移除
                    strs.remove(position);
                    // 更新ListView
                    adapter.notifyDataSetChanged();
                }
            });
            return view;
        }

    }

    private class ViewHolder {
        private TextView tv;
        private ImageView iv;
    }
}