android入门学习-天气预报app（一）
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2022-04-17 20:11:12
引言 学习《android第一行代码》根据书本开发的天气预报app，主要用于熟练操作android开发（android studio3.0平台）。 今天主要分享一下从服务器上获取天气信息，通过ListView绑定数据的操作（可以采用RecycleView），然后进行页面点击跳转。 一、 服务器返回数 ......
引言
学习《android第一行代码》根据书本开发的天气预报app，主要用于熟练操作android开发（android studio3.0平台）。
今天主要分享一下从服务器上获取天气信息，通过ListView绑定数据的操作（可以采用RecycleView），然后进行页面点击跳转。
一、 服务器返回数据预览
通过本书作者提供的访问地址，，直接打开可以访问到全国各地的天气信息，
[
{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"天津"},{"id":4,"name":"重庆"},
{"id":5,"name":"香港"},{"id":6,"name":"澳门"},{"id":7,"name":"*"},{"id":8,"name":"黑龙江"},
{"id":9,"name":"吉林"},{"id":10,"name":"辽宁"},{"id":11,"name":"内蒙古"},{"id":12,"name":"河北"},
{"id":13,"name":"河南"},{"id":14,"name":"山西"},{"id":15,"name":"山东"},{"id":16,"name":"江苏"},
{"id":17,"name":"浙江"},{"id":18,"name":"福建"},{"id":19,"name":"江西"},{"id":20,"name":"安徽"},
{"id":21,"name":"湖北"},{"id":22,"name":"湖南"},{"id":23,"name":"广东"},{"id":24,"name":"广西"},
{"id":25,"name":"海南"},{"id":26,"name":"贵州"},{"id":27,"name":"云南"},{"id":28,"name":"四川"},
{"id":29,"name":"*"},{"id":30,"name":"陕西"},{"id":31,"name":"宁夏"},{"id":32,"name":"甘肃"},
{"id":33,"name":"青海"},{"id":34,"name":"*"}
]
如上面看到的可以获取到各省的信息，通过id可以进一步的获取市县的信息。
二、创建本地数据存储
根据服务器中获取的数据属性，创建Province、City、County三个数据表分别存储省、市、县的信息。
创建数据表采用Litepal，这里需要导入外部库，需要在build.gradle中添加
implementation 'org.litepal.android:core:1.4.1'
（注implemention为android3.0以上版本才有的，与compile并不完全一样，这里不多做解释，2.0版本采用compile不影响
同时在加载外部库时可能出现无法引用的问题，请清理项目后重新build）
后面1.4.1是版本号，可以查询官网获取最新版本
下面附上三个数据表类，由于是采用Litepal需要继承DataSupport
public class Province extends DataSupport {
private int id;
private String provinceName;
private int provinceCode;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getProvinceName() {
return provinceName;
}
public void setProvinceName(String provinceName) {
this.provinceName = provinceName;
}
public int getProvinceCode() {
return provinceCode;
}
public void setProvinceCode(int provinceCode) {
this.provinceCode = provinceCode;
}
}
public class City extends DataSupport {
private int id;
private String cityName;
private int cityCode;
private int provinceId;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCityName() {
return cityName;
}
public void setCityName(String cityName) {
this.cityName = cityName;
}
public int getCityCode() {
return cityCode;
}
public void setCityCode(int cityCode) {
this.cityCode = cityCode;
}
public int getProvinceId() {
return provinceId;
}
public void setProvinceId(int provinceId) {
this.provinceId = provinceId;
}
}
public class County extends DataSupport {
private int id;
private String countyName;
private String weatherId;
private int cityId;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCountyName() {
return countyName;
}
public void setCountyName(String countyName) {
this.countyName = countyName;
}
public String getWeatherId() {
return weatherId;
}
public void setWeatherId(String weatherId) {
this.weatherId = weatherId;
}
public int getCityId() {
return cityId;
}
public void setCityId(int cityId) {
this.cityId = cityId;
}
}
这三个类用来生成本地数据库
接下来新建一个litepal.xml配置文件，在main目录下新建assets配置文件夹，添加litepal.xml
<litepal>
<dbname value ="cool_weather"/>
<version value = "1"/>
<list>
<mapping class="com.coolweather2.db.Province"/>
<mapping class="com.coolweather2.db.County"/>
<mapping class="com.coolweather2.db.City"/>
</list>
</litepal>
此文件通过Litepal创建了cool_weather数据库同时添加了三个数据表
最后在androidmanifest.xml中添加LitepalApplication，如下
这样Litepal可以全局调用Context，注意如果不加，默认启动时会初始化Application类
三、编写工具包类
3.1HttpUtil
public class HttpUtil {
public static void sendOkHttpRequest(String address,okhttp3.Callback callback) {
OkHttpClient client = new OkHttpClient();
//request属于不能继承的类初始化Builder静态类调用url方法，最后调用Requset的build方法
Request request = new Request.Builder().url(address).build();
client.newCall(request).enqueue(callback);
}
}
主要用来想服务器发送请求，创建request并设置好其地址，通过client发起请求并设置callback回调请求
3.2Utility
public class Utillty {
/*解析和处理服务器返回的省级数据*/
public static boolean handleProvinceResponse(String response) {
if(!TextUtils.isEmpty(response)) {
try
{
JSONArray allProvinces = new JSONArray(response);
for(int i = 0;i < allProvinces.length(); i++) {
JSONObject privinceObject = allProvinces.getJSONObject(i);
Province province = new Province();
province.setProvinceName(privinceObject.getString("name"));
province.setProvinceCode(privinceObject.getInt("id"));
province.save();
}
return true;
}
catch (JSONException ex) {
ex.printStackTrace();
}
}
return false;
}
/**
* 解析和处理服务器返回的市级数据
* */
public static boolean handleCityResponse(String response,int provinceId) {
if(!TextUtils.isEmpty(response)) {
try
{
JSONArray allCities = new JSONArray(response);
for(int i = 0;i < allCities.length(); i++) {
JSONObject cityObject = allCities.getJSONObject(i);
City city = new City();
city.setCityName(cityObject.getString("name"));
city.setCityCode(cityObject.getInt("id"));
city.setProvinceId(provinceId);
city.save();
}
return true;
}
catch (JSONException ex) {
ex.printStackTrace();
}
}
return false;
}
/**
* 解析和处理服器返回的县级数据
* */
public static boolean handleCountyResponse(String response,int cityId) {
if(!TextUtils.isEmpty(response)) {
try
{
JSONArray allCountries = new JSONArray(response);
for(int i = 0;i < allCountries.length(); i++) {
JSONObject countyObject = allCountries.getJSONObject(i);
County county = new County();
county.setCountyName(countyObject.getString("name"));
county.setWeatherId(countyObject.getString("weather_id"));
county.setCityId(cityId);
county.save();
}
return true;
}
catch (JSONException ex) {
ex.printStackTrace();
}
}
return false;
}
主要处理从服务器返回的数据，根据最开始的数据预览可以看到，服务器返回的数据是以Json格式输出的
那么这个工具类就是对json数据的分析处理，通过JSONArray数组将json数据保存在本地数据库
有这里的json数据比较简单，直接进行解析，不采用GSON
四、创建碎片布局
碎片有利于代码的复用，可以尝试将自己的很多功能都通过碎片进行封装
创建碎片会生成两个文件，一个是碎片的布局文件choose_area.xml，一个是ChooseAreaFragment.class
4.1布局文件
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#fff">
<RelativeLayout
android:layout_width = "match_parent"
android:layout_height = "?attr/actionBarSize"
android:background="?attr/colorPrimary">
<TextView
android:id="@+id/title_text"
android:layout_centerInParent="true"
android:textColor="#fff"
android:textSize="20sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="@+id/back_button"
android:layout_width="25dp"
android:layout_marginLeft="10dp"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:layout_height="25dp"
android:background="@drawable/ic_launcher_background"/>
</RelativeLayout>
<ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"></ListView>
</LinearLayout>
简单的两个布局，整体用线性布局垂直对齐方式，头部标题栏采用RecycleLayout布局，设置一个回调按钮和一个标题文本框
底部一个listview用来显示天气列表
4.2ChooseAreaFragment.class
public class ChooseAreaFragment extends Fragment {
public static final int LEVEL_PROVINCE = 0;
public static final int LEVEL_CITY = 1;
public static final int LEVEL_COUNTY = 2;
private ProgressDialog progressDialog;
private TextView titleText;
private Button backButton;
private ListView listView;
private ArrayAdapter<String> adapter;
private List<String> dataList = new ArrayList<>();
private List<Province> provinceList;
private List<City> cityList;
private List<County> countyList;
private Province selectedProvince;
private City selectedCity;
private int currentLevel;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.choose_area,container,false);
titleText = (TextView)view.findViewById(R.id.title_text);
backButton = (Button)view.findViewById(R.id.back_button);
listView = (ListView)view.findViewById(R.id.list_view);
adapter = new ArrayAdapter<String>(getContext(), R.layout.support_simple_spinner_dropdown_item,dataList);
listView.setAdapter(adapter);
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
queryProvinces();
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
if(currentLevel == LEVEL_PROVINCE) {
selectedProvince = provinceList.get(position);
queryCities();
}
else if (currentLevel == LEVEL_CITY) {
selectedCity = cityList.get(position);
queryCountries();
}
}
});
backButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (currentLevel == LEVEL_COUNTY) {
queryCities();
}
else if (currentLevel == LEVEL_CITY) {
queryProvinces();
}
}
});
}
/**
* 查询所有省，查数据库，再查服务器
*/
private void queryProvinces() {
titleText.setText("中国");
backButton.setVisibility(View.GONE);
provinceList = DataSupport.findAll(Province.class);
if(provinceList.size()>0) {
dataList.clear();
for (Province province :
provinceList) {
dataList.add(province.getProvinceName());
}
adapter.notifyDataSetChanged();
listView.setSelection(0);
currentLevel = LEVEL_PROVINCE;
}
else {
//服务器查询
String address = "http://guolin.tech/api/china";
queryFromServer(address,"province");
}
}
/**
* 查询市
*/
private void queryCities() {
titleText.setText(selectedProvince.getProvinceName());
backButton.setVisibility(View.VISIBLE);
cityList = DataSupport.where("provinceid = ?",String.valueOf(selectedProvince.getId()))
.find(City.class);
if (cityList.size()>0) {
dataList.clear();
for (City city :
cityList) {
dataList.add(city.getCityName());
}
adapter.notifyDataSetChanged();
listView.setSelection(0);
currentLevel = LEVEL_CITY;
}
else {
//查询服务器
int provinceCode = selectedProvince.getProvinceCode();
String address = "http://guolin.tech/api/china/" + provinceCode;
queryFromServer(address,"city");
}
}
/**
* 查询县
*/
private void queryCountries(){
titleText.setText(selectedCity.getCityName());
backButton.setVisibility(View.VISIBLE);
countyList = DataSupport.where("cityid = ?",String.valueOf(selectedCity.getId()))
.find(County.class);
if (countyList.size()>0) {
dataList.clear();
for (County county :
countyList) {
dataList.add(county.getCountyName());
}
adapter.notifyDataSetChanged();
listView.setSelection(0);
currentLevel = LEVEL_COUNTY;
}
else {
//访问服务器
int provinceCode = selectedProvince.getProvinceCode();
int cityCode = selectedCity.getCityCode();
String address = "http://guolin.tech/api/china/" + provinceCode + "/" + cityCode;
Toast.makeText(getContext(),provinceCode +"/" + cityCode,Toast.LENGTH_LONG).show();
queryFromServer(address,"county ");
}
}
/**
* 从服务器查询
*/
private void queryFromServer(String address,final String type) {
showProgressDialog();
Toast.makeText(getContext(),type,Toast.LENGTH_SHORT).show();
HttpUtil.sendOkHttpRequest(address, new Callback() {
@Override
public void onFailure(Call call, IOException e) {
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
closeProgressDialog();
Toast.makeText(getContext(),"加载失败!",Toast.LENGTH_SHORT).show();
}
});
}
@Override
public void onResponse(Call call, Response response) throws IOException {
String responText = response.body().string();
boolean result = false;
if("province".equals(type)) {
result = Utillty.handleProvinceResponse(responText);
}
else if ("city".equals(type)) {
result = Utillty.handleCityResponse(responText,selectedProvince.getId());
}
else if ("county".equals(type)){
//Toast.makeText(getContext(),"aaaaa",Toast.LENGTH_LONG).show();
result = Utillty.handleCountyResponse(responText,selectedCity.getId());
}
//Toast.makeText(getContext(),"" + result,Toast.LENGTH_SHORT).show();
if (result) {
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
closeProgressDialog();
if("province".equals(type)) {
queryProvinces();
}
else if ("city".equals(type)) {
queryCities();
}
else if ("county".equals(type)){
queryCountries();
}
}
});
}
}
});
}
/**
* 显示进度框
*/
private void showProgressDialog() {
if(progressDialog == null) {
progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("正在加载");
progressDialog.setCanceledOnTouchOutside(false);
}
progressDialog.show();
}
/**
* 关闭进度对话框
*/
private void closeProgressDialog() {
if (progressDialog != null) {
progressDialog.dismiss();
}
}
这里我把不需要用到的方法删除，只留下onCreateView和onActivityCreated这两个方法
一个表示创建布局，主要用来加载布局同时对部分数据进行初始化
onActivityCreated显然是在布局加载完之后才触发的，主要的功能都在这里面实现
主要实现的是listview的跳转功能，判断当前是那一级别的数据从而点击时获取下一级别的数据，
如当前点击“江苏”，首先返回按钮显示，标题改为“江苏”，然后优先查询数据库信息，当没有找到时再向服务器发送请求
五、主活动中加载碎片
修改main布局中的文件
通过name在初始化时运行碎片
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".activity.MainActivity">
<fragment
android:id="@+id/choose_area_fragment"
android:name="com.coolweather2.fragment.ChooseAreaFragment"
android:layout_width="match_parent"
android:layout_height="match_parent">
</fragment>
</FrameLayout>
注意由于碎片中设置过标题，需要在styles.xml中修改默认标题
最后需要设置网络访问权限（Androidmanifest.xml）
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