引言

學習《android第一行代碼》根據書本開發的天氣預報app，主要用于熟練操作android開發（android studio3.0平臺）。

今天主要分享一下從服務器上獲取天氣信息，通過ListView綁定數據的操作（可以采用RecycleView），然后進行頁面點擊跳轉。

一、 服務器返回數據預覽

通過本書作者提供的訪問地址，guolin.tech/api/china，直接打開可以訪問到全國各地的天氣信息，guolin.tech/api/china/16/116

（如點擊無法打開，請直接復制鏈接在瀏覽器中訪問）

[
{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"天津"},{"id":4,"name":"重慶"},
{"id":5,"name":"香港"},{"id":6,"name":"澳門"},{"id":7,"name":"臺灣"},{"id":8,"name":"黑龍江"},
{"id":9,"name":"吉林"},{"id":10,"name":"遼寧"},{"id":11,"name":"內蒙古"},{"id":12,"name":"河北"},
{"id":13,"name":"河南"},{"id":14,"name":"山西"},{"id":15,"name":"山東"},{"id":16,"name":"江蘇"},
{"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":"廣東"},{"id":24,"name":"廣西"},
{"id":25,"name":"海南"},{"id":26,"name":"貴州"},{"id":27,"name":"云南"},{"id":28,"name":"四川"},
{"id":29,"name":"西藏"},{"id":30,"name":"陜西"},{"id":31,"name":"寧夏"},{"id":32,"name":"甘肅"},
{"id":33,"name":"青海"},{"id":34,"name":"新疆"}
]

如上面看到的可以獲取到各省的信息，通過id可以進一步的獲取市縣的信息。

二、創建本地數據存儲

根據服務器中獲取的數據屬性，創建Province、City、County三個數據表分別存儲省、市、縣的信息。

創建數據表采用Litepal，這里需要導入外部庫，需要在build.gradle中添加

implementation 'org.litepal.android:core:1.4.1'
（注implemention為android3.0以上版本才有的，與compile并不完全一樣，這里不多做解釋，2.0版本采用compile不影響
同時在加載外部庫時可能出現無法引用的問題，請清理項目后重新build）

?后面1.4.1是版本號，可以查詢官網獲取最新版本

下面附上三個數據表類，由于是采用Litepal需要繼承DataSupport

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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;} } Province省數據表 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;} } City市數據表 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;} } County縣數據表

這三個類用來生成本地數據庫

接下來新建一個litepal.xml配置文件，在main目錄下新建assets配置文件夾，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> litepal.xml

此文件通過Litepal創建了cool_weather數據庫同時添加了三個數據表

最后在androidmanifest.xml中添加LitepalApplication，如下

這樣Litepal可以全局調用Context，注意如果不加，默認啟動時會初始化Application類

三、編寫工具包類

3.1HttpUtil

public class HttpUtil {public static void sendOkHttpRequest(String address,okhttp3.Callback callback) {OkHttpClient client = new OkHttpClient();//request屬于不能繼承的類初始化Builder靜態類調用url方法，最后調用Requset的build方法Request request = new Request.Builder().url(address).build();client.newCall(request).enqueue(callback);} } HttpUtil.class

主要用來想服務器發送請求，創建request并設置好其地址，通過client發起請求并設置callback回調請求

3.2Utility

public class Utillty {/*解析和處理服務器返回的省級數據*/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;}/*** 解析和處理服務器返回的市級數據* */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;}/*** 解析和處理服器返回的縣級數據* */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;} Utility.class

主要處理從服務器返回的數據，根據最開始的數據預覽可以看到，服務器返回的數據是以Json格式輸出的

那么這個工具類就是對json數據的分析處理，通過JSONArray數組將json數據保存在本地數據庫

有這里的json數據比較簡單，直接進行解析，不采用GSON

四、創建碎片布局

?碎片有利于代碼的復用，可以嘗試將自己的很多功能都通過碎片進行封裝

創建碎片會生成兩個文件，一個是碎片的布局文件choose_area.xml，一個是ChooseAreaFragment.class

4.1布局文件

<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"android:background="#fff"><RelativeLayoutandroid:layout_width = "match_parent"android:layout_height = "?attr/actionBarSize"android:background="?attr/colorPrimary"><TextViewandroid:id="@+id/title_text"android:layout_centerInParent="true"android:textColor="#fff"android:textSize="20sp"android:layout_width="wrap_content"android:layout_height="wrap_content" /><Buttonandroid: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><ListViewandroid:id="@+id/list_view"android:layout_width="match_parent"android:layout_height="match_parent"></ListView></LinearLayout> choose_area.xml

簡單的兩個布局，整體用線性布局垂直對齊方式，頭部標題欄采用RecycleLayout布局，設置一個回調按鈕和一個標題文本框

底部一個listview用來顯示天氣列表

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@Overridepublic 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;}@Overridepublic void onActivityCreated(@Nullable Bundle savedInstanceState) {super.onActivityCreated(savedInstanceState);queryProvinces();listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {@Overridepublic 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() {@Overridepublic void onClick(View v) {if (currentLevel == LEVEL_COUNTY) {queryCities();}else if (currentLevel == LEVEL_CITY) {queryProvinces();}}});}/*** 查詢所有省，查數據庫，再查服務器*/private void queryProvinces() {titleText.setText("中國");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 {//服務器查詢String address = "http://guolin.tech/api/china";queryFromServer(address,"province");}}/*** 查詢市*/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 {//查詢服務器int provinceCode = selectedProvince.getProvinceCode();String address = "http://guolin.tech/api/china/" + provinceCode;queryFromServer(address,"city");}}/*** 查詢縣*/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 {//訪問服務器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 ");}}/*** 從服務器查詢*/private void queryFromServer(String address,final String type) {showProgressDialog();Toast.makeText(getContext(),type,Toast.LENGTH_SHORT).show();HttpUtil.sendOkHttpRequest(address, new Callback() {@Overridepublic void onFailure(Call call, IOException e) {getActivity().runOnUiThread(new Runnable() {@Overridepublic void run() {closeProgressDialog();Toast.makeText(getContext(),"加載失敗!",Toast.LENGTH_SHORT).show();}});}@Overridepublic 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() {@Overridepublic void run() {closeProgressDialog();if("province".equals(type)) {queryProvinces();}else if ("city".equals(type)) {queryCities();}else if ("county".equals(type)){queryCountries();}}});}}});}/*** 顯示進度框*/private void showProgressDialog() {if(progressDialog == null) {progressDialog = new ProgressDialog(getActivity());progressDialog.setMessage("正在加載");progressDialog.setCanceledOnTouchOutside(false);}progressDialog.show();}/*** 關閉進度對話框*/private void closeProgressDialog() {if (progressDialog != null) {progressDialog.dismiss();}} ChooseAreaFragment

這里我把不需要用到的方法刪除，只留下onCreateView和onActivityCreated這兩個方法

一個表示創建布局，主要用來加載布局同時對部分數據進行初始化

onActivityCreated顯然是在布局加載完之后才觸發的，主要的功能都在這里面實現

主要實現的是listview的跳轉功能，判斷當前是那一級別的數據從而點擊時獲取下一級別的數據，

如當前點擊“江蘇”，首先返回按鈕顯示，標題改為“江蘇”，然后優先查詢數據庫信息，當沒有找到時再向服務器發送請求

?五、主活動中加載碎片

修改main布局中的文件

通過name在初始化時運行碎片

<?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"><fragmentandroid:id="@+id/choose_area_fragment"android:name="com.coolweather2.fragment.ChooseAreaFragment"android:layout_width="match_parent"android:layout_height="match_parent"></fragment></FrameLayout> layout

注意由于碎片中設置過標題，需要在styles.xml中修改默認標題

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最后需要設置網絡訪問權限（Androidmanifest.xml）

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轉載于:https://www.cnblogs.com/lisd/p/9304794.html

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