android入门学习-天气预报app（一）

摘要：引言学习第一行代码根据书本开发的天气预报，主要用于熟练操作开发平台。二创建本地数据存储根据服务器中获取的数据属性，创建三个数据表分别存储省市县的信息。

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。

通过本书作者提供的访问地址，guolin.tech/api/china，直接打开可以访问到全国各地的天气信息，guolin.tech/api/china/16/116

（如点击无法打开，请直接复制链接在浏览器中访问）

[
 {"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":"台湾"},{"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":"西藏"},{"id":30,"name":"陕西"},{"id":31,"name":"宁夏"},{"id":32,"name":"甘肃"},
 {"id":33,"name":"青海"},{"id":34,"name":"新疆"}
]

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。

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

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

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

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

 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

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

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 adapter;
    private List dataList = new ArrayList<>();

    private List provinceList;
    private List cityList;
    private List 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(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

修改main布局中的文件

通过name在初始化时运行碎片

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）