项目：cityjsonlist
思路：
- 1.通过IO流读取本地asset目录下的cityjson.json文件返回String类型的response。
- 2.通过gson解析将数据保存在List<CityAllResults> cityResultLists中
- 3.将获取的省、城市、区/县保存在对应的List中，为了产生级联效果，将单个province(string)与获取完整的city的List保存在HashMap中，产生一一对应关系
-------------以上步骤为保存数据----------- - 4.省份spinner控件首先设置数据样式，同时updateCity方法获取存在HashMap省份对应的city的List，以此类推。
在此过程中出现空指针异常错误
有两方面的原因：1. mContext未赋值 2. 存放的数据变量填写错误。
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项目：TestcityLists2
在先前项目中把存储省份的操作提取为单独的一个方法：
package com.example.testcitylists.db;
import android.content.Context;
import android.widget.ArrayAdapter;
/**
* 查询城市信息类
*/
public class CityDbQuery {
private static final String TAG = "TAG";
private String city_url;
private Context mContext;
//适配器
private ArrayAdapter<String> mProAdapter;
private ArrayAdapter<String> mCityAdapter;
private ArrayAdapter<String> mAreaAdapter;
//存放城市信息的数组
private String[] mProvinceDatas;
private String[] mCityDatas;
private String[] mAreaDatas;
//存放 province — city — area 相对应的HashMap
private Map<String, String[]> mCityMaps;
private Map<String, String[]> mAreaMaps;
public CityDbQuery(Context context) {
this.mContext=context;
}
/**
* 本地文件解析
*/
public void beginLocalJsonParse() {
mAreaMaps = new HashMap<>();
mCityMaps = new HashMap<>();
String response = HttpLocalUtils.sendRequest(mContext, "cityjson.json");
Gson gson = new Gson();
List<CityAllResults> cityResultLists = gson.fromJson(response, new TypeToken<List<CityAllResults>>() {
}.getType());
mProvinceDatas = new String[cityResultLists.size()];
String province = null;
for (int i = 0; i < cityResultLists.size(); i++) {
CityAllResults cityAllResults = cityResultLists.get(i);
//获取省份
if (cityAllResults.getProvice() != null) {
province = cityAllResults.getProvice();
//存在 省 数组中
mProvinceDatas[i] = province;
} else {
mProvinceDatas[i] = "unknown province";
}
List<CityAllResults.CityBean> cityLists = cityAllResults.getCityLists();
mCityDatas = new String[cityLists.size()];
for (int j = 0; j < cityLists.size(); j++) {
CityAllResults.CityBean cityBean = cityLists.get(j);
//获取城市信息
String city = cityBean.getCity();
//存在 城市 数组中
mCityDatas[j] = city;
List<String> areaLists = cityBean.getAreaLists();
//Log.i(TAG, "city------" + mCityDatas[j]);
mAreaDatas = new String[areaLists.size()];
for (int k = 0; k < areaLists.size(); k++) {
//找到区/县信息
String area = areaLists.get(k);
//存在area数组中
mAreaDatas[k] = area;
// Log.w(TAG, "area------" + mAreaDatas[k]);
}
//在 area 取出完之后，将mAreaDatas和对应的city存在mAreaMaps中，有一一对应关系
mAreaMaps.put(city, mAreaDatas);
}
//在 city 取出完之后，将province和对应的mAreaDatas存在mCityMaps中，有一一对应关系
mCityMaps.put(province, mCityDatas);
}
}
/**
* 获取省份信息
* @return：返回list<省>
*/
public List<String> loadProvince(){
List<String>list=new ArrayList<>();
for (int i=0;i<mProvinceDatas.length;i++)
if(mProvinceDatas !=null){
list.add(mProvinceDatas[i]);
}
return list;
}
/**
* 根据选定的省份获取HashMap对应的城市列表
* @param selectedPro 已选城市
* @return 获取 市级别 信息，返回list<市>
*/
public List<String>loadCity(String selectedPro){
List<String>list=new ArrayList<>();
String[] cities = mCityMaps.get(selectedPro);
for (int i=0;i<cities.length;i++) {
if (cities != null) {
list.add(cities[i]);
}
}
return list;
}
/**
* 根据选定的城市获取HashMap对应的 区/县 列表
* @param selectedCity
* @return 获取区/县级别信息，返回list<区/县>
*/
public List<String>loadArea(String selectedCity){
List<String>list=new ArrayList<>();
String[] areas = mAreaMaps.get(selectedCity);
for (int i=0;i<areas.length;i++) {
if(areas!=null){
list.add(areas[i]);
}
}
return list;
}
}
关于主activity文件
package com.example.testcitylists.activity;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.example.testcitylists.db.CityDbQuery;
import com.example.testcitylists.R;
import java.util.ArrayList;
import java.util.List;
import static android.content.ContentValues.TAG;
public class CityActivity extends Activity{
private static final int LEVEL_PRO=0;
private static final int LEVEL_CITY=1;
private static final int LEVEL_COUNTY=2;
private int currentLevel;
private ListView lv_cityLists;
private List<String> dataLists;
private ArrayAdapter<String>dataAdapter;
private Context mContext;
private CityDbQuery cityqb;
private String selectedPro;
private String selectedCity;
private String selectedCounty;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_city_activity);
mContext=this;
findview();
bindview();
queryPro();
}
/**
* loadProvince方法获取省份 列表，将省份列表复制到datalists中；
* ---同时设置currentLevel为省份级别
*/
private void queryPro() {
List<String> mProLists = cityqb.loadProvince();
if(mProLists!=null){
dataLists.clear();
for (String pro:mProLists) {
//--
dataLists.add(pro);
dataAdapter.notifyDataSetChanged();
currentLevel=LEVEL_PRO;
}
}
}
/**
* 设置listview的item点击事件:调用chooseInfo方法
*/
private void bindview() {
//点击后执行
lv_cityLists.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
chooseInfo(position);
}
});
}
/**
* 根据currentLevel的值执行不同的动作：
* 省：获取到选中省份，并调用queryCity方法--①为了重新设置datalists的数据源②并刷新listview
* ③ currentLevel也得更改否则没法继续进行
* @param position 点击item对应的位置，可以获取到你点击了什么
*/
private void chooseInfo(int position) {
switch (currentLevel) {
case LEVEL_PRO:
//这里我用了datalist而不是mProLists
selectedPro=dataLists.get(position);
queryCity(selectedPro);
break;
case LEVEL_CITY:
selectedCity=dataLists.get(position);
queryCounty(selectedCity);
break;
case LEVEL_COUNTY:
selectedCounty=dataLists.get(position);
Log.e(TAG, "chooseInfo:"+selectedPro+selectedCity+selectedCounty );
break;
}
}
private void queryCounty(String selectedCity) {
List<String> counties = cityqb.loadArea(selectedCity);
if (counties != null) {
dataLists.clear();
for (String county : counties) {
dataLists.add(county);
dataAdapter.notifyDataSetChanged();
currentLevel=LEVEL_COUNTY;
}
}
}
private void queryCity(String selectedPro) {
List<String> cities = cityqb.loadCity(selectedPro);
if(cities.size()>0){
dataLists.clear();
for (String city:cities){
dataLists.add(city);
dataAdapter.notifyDataSetChanged();
currentLevel=LEVEL_CITY;
}
}
}
/**
* 找到对应控件，并设置dataAdapter的数据源为dataLists;
* 同时实例化CityDbQuery并调用beginLocalJsonParse方法完成数据查询
*/
private void findview() {
lv_cityLists= (ListView) findViewById(R.id.lv_cityList);
dataLists=new ArrayList<>();
dataAdapter=new ArrayAdapter<String>(mContext,android.R.layout.simple_list_item_1,dataLists);
lv_cityLists.setAdapter(dataAdapter);
cityqb =new CityDbQuery(mContext);
cityqb.beginLocalJsonParse();
}
}
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