最近项目要做一个，类似淘宝手机客户端的，选择收货地址的三级联动滚动选择组件，下面是它的大致界面截图：

在IOS中有个叫UIPickerView的选择器，并且在dataSource中定义了UIPickerView的数据源和定制内容，所以用只要熟悉它的基本用法，要实现这么个三级联动滑动选择是挺简单的。 

言归正传，今天讨论的是在Android里面如何来实现这么个效果，那么如何实现呢？？？ 相信部分童鞋首先想到的是android.widget.DatePicker和android.widget.TimePicker，因为它们的样子长得很像，事实就是它们仅仅是长得相而已，Google在设计这个两个widget的时候，并没有提供对外的数据源适配接口，带来的问题就是，我们只能通过它们来选择日期和时间，至于为什么这样设计，如果有童鞋知道，请给我留言，Thanks~

DatePicker.class包含的方法截图：

 全都是关于时间获取用的方法.

好了，既然在Android中没办法偷懒的用一个系统widget搞定，那么只能自己来自定义view来实现了，这篇就围绕这个来展开分享一下，我在项目中实现这个的全过程。首先是做了下开源代码调研，在github上面有一个叫做 android-wheel 的开源控件, 代码地址https://github.com/maarek/android-wheel

是一个非常好用的组件，对于数据适配接口的抽取和事件的回调都做了抽取，代码的耦合度低，唯一不足就是在界面的定制这块，如果你需要做更改，需要去动源代码的。我这里在界面的代码做了改动，放在我的项目src目录下了：

在此次项目中，省市区及邮编的数据是放在了assets/province_data.xml里面，是产品经理花了好几天时间整理的，绝对是最齐全和完善了，辛苦辛苦！！！

关于XML的解析，一共有SAX、PULL、DOM三种解析方式，这里就不讲了，可以看我的前面的几篇学习的文章：

Android解析XML方式(一)使用SAX解析

Android解析XML方式(二)使用PULL解析XML

Android解析XML方式(三)使用DOM解析XML

此次项目中使用的是SAX解析方式，因为它占用内存少，并且速度快，数据解析代码写在了 com.mrwujay.cascade.service/XmlParserHandler.java中，代码如下：

package com.mrwujay.cascade.service;import java.util.ArrayList;import java.util.List;import org.xml.sax.Attributes;import org.xml.sax.SAXException;import org.xml.sax.helpers.DefaultHandler;import com.mrwujay.cascade.model.CityModel;import com.mrwujay.cascade.model.DistrictModel;import com.mrwujay.cascade.model.ProvinceModel;public class XmlParserHandler extends DefaultHandler {/** * 存储所有的解析对象 */private List provinceList = new ArrayList();   public XmlParserHandler() {}public List getDataList() {return provinceList;}@Overridepublic void startDocument() throws SAXException {// 当读到第一个开始标签的时候，会触发这个方法}ProvinceModel provinceModel = new ProvinceModel();CityModel cityModel = new CityModel();DistrictModel districtModel = new DistrictModel();@Overridepublic void startElement(String uri, String localName, String qName,Attributes attributes) throws SAXException {// 当遇到开始标记的时候，调用这个方法if (qName.equals("province")) {provinceModel = new ProvinceModel();provinceModel.setName(attributes.getValue(0));provinceModel.setCityList(new ArrayList());} else if (qName.equals("city")) {cityModel = new CityModel();cityModel.setName(attributes.getValue(0));cityModel.setDistrictList(new ArrayList());} else if (qName.equals("district")) {districtModel = new DistrictModel();districtModel.setName(attributes.getValue(0));districtModel.setZipcode(attributes.getValue(1));}}@Overridepublic void endElement(String uri, String localName, String qName)throws SAXException {// 遇到结束标记的时候，会调用这个方法if (qName.equals("district")) {cityModel.getDistrictList().add(districtModel);        } else if (qName.equals("city")) {        provinceModel.getCityList().add(cityModel);        } else if (qName.equals("province")) {        provinceList.add(provinceModel);        }}@Overridepublic void characters(char[] ch, int start, int length)throws SAXException {}}

通过XmlParserHandler.java提供的getDataList（）方法获取得到，之后再进行拆分放到省、市、区不同的HashMap里面方便做数据适配。

这里是它的具体实现代码：

protected void initProvinceDatas(){List provinceList = null;    AssetManager asset = getAssets();        try {            InputStream input = asset.open("province_data.xml");            // 创建一个解析xml的工厂对象SAXParserFactory spf = SAXParserFactory.newInstance();// 解析xmlSAXParser parser = spf.newSAXParser();XmlParserHandler handler = new XmlParserHandler();parser.parse(input, handler);input.close();// 获取解析出来的数据provinceList = handler.getDataList();//*/ 初始化默认选中的省、市、区if (provinceList!= null && !provinceList.isEmpty()) {mCurrentProviceName = provinceList.get(0).getName();List cityList = provinceList.get(0).getCityList();if (cityList!= null && !cityList.isEmpty()) {mCurrentCityName = cityList.get(0).getName();List districtList = cityList.get(0).getDistrictList();mCurrentDistrictName = districtList.get(0).getName();mCurrentZipCode = districtList.get(0).getZipcode();}}//*/mProvinceDatas = new String[provinceList.size()];        for (int i=0; i< provinceList.size(); i++) {        mProvinceDatas[i] = provinceList.get(i).getName();        List cityList = provinceList.get(i).getCityList();        String[] cityNames = new String[cityList.size()];        for (int j=0; j< cityList.size(); j++) {        cityNames[j] = cityList.get(j).getName();        List districtList = cityList.get(j).getDistrictList();        String[] distrinctNameArray = new String[districtList.size()];        DistrictModel[] distrinctArray = new DistrictModel[districtList.size()];        for (int k=0; k

initProvinceDatas();mViewProvince.setViewAdapter(new ArrayWheelAdapter(MainActivity.this, mProvinceDatas));// 设置可见条目数量mViewProvince.setVisibleItems(7);mViewCity.setVisibleItems(7);mViewDistrict.setVisibleItems(7);updateCities();updateAreas();

/** * Wheel scrolled listener interface. */public interface OnWheelScrollListener {/** * Callback method to be invoked when scrolling started. * @param wheel the wheel view whose state has changed. */void onScrollingStarted(WheelView wheel);/** * Callback method to be invoked when scrolling ended. * @param wheel the wheel view whose state has changed. */void onScrollingFinished(WheelView wheel);}

/** * Wheel clicked listener interface. * 
The onItemClicked() method is called whenever a wheel item is clicked * 
 New Wheel position is set * 
 Wheel view is scrolled */public interface OnWheelClickedListener {    /**     * Callback method to be invoked when current item clicked     * @param wheel the wheel view     * @param itemIndex the index of clicked item     */    void onItemClicked(WheelView wheel, int itemIndex);}

/** * Wheel changed listener interface. * 
The onChanged() method is called whenever current wheel positions is changed: * 
 New Wheel position is set * 
 Wheel view is scrolled */public interface OnWheelChangedListener {/** * Callback method to be invoked when current item changed * @param wheel the wheel view whose state has changed * @param oldValue the old value of current item * @param newValue the new value of current item */void onChanged(WheelView wheel, int oldValue, int newValue);}

/** * key - 省 value - 市 */protected Map mCitisDatasMap = new HashMap();/** * key - 市 values - 区 */protected Map mDistrictDatasMap = new HashMap();/** * key - 区 values - 邮编 */protected Map mZipcodeDatasMap = new HashMap(); 

@Overridepublic void onChanged(WheelView wheel, int oldValue, int newValue) {// TODO Auto-generated method stubif (wheel == mViewProvince) {updateCities();} else if (wheel == mViewCity) {updateAreas();} else if (wheel == mViewDistrict) {mCurrentDistrictName = mDistrictDatasMap.get(mCurrentCityName)[newValue];mCurrentZipCode = mZipcodeDatasMap.get(mCurrentDistrictName);}}/** * 根据当前的市，更新区WheelView的信息 */private void updateAreas() {int pCurrent = mViewCity.getCurrentItem();mCurrentCityName = mCitisDatasMap.get(mCurrentProviceName)[pCurrent];String[] areas = mDistrictDatasMap.get(mCurrentCityName);if (areas == null) {areas = new String[] { "" };}mViewDistrict.setViewAdapter(new ArrayWheelAdapter(this, areas));mViewDistrict.setCurrentItem(0);}/** * 根据当前的省，更新市WheelView的信息 */private void updateCities() {int pCurrent = mViewProvince.getCurrentItem();mCurrentProviceName = mProvinceDatas[pCurrent];String[] cities = mCitisDatasMap.get(mCurrentProviceName);if (cities == null) {cities = new String[] { "" };}mViewCity.setViewAdapter(new ArrayWheelAdapter(this, cities));mViewCity.setCurrentItem(0);updateAreas();}