天气开发4——第二行代码（酷欧天气）

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后台

我们使用Alarm来实现后台的定时自动更新

        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);        long TriggerAtTime = SystemClock.elapsedRealtime()+8*60*60*1000;//8小时        PendingIntent pi = PendingIntent.getService(this, 0, i, 0);        manager.cancel(pi);        manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, TriggerAtTime, pi);

在服务中，我们在onStartCommand中实现定时自动下载功能，因为一旦服务启动后，onStartComand就会无限期执行下去。我们要记得在WeatherActivity中开启服务，因为此时所有数据都已经准备好，并且完整的呈现出来：

//显示天气数据    private void showWeatherInfo(Weather weather) {        Intent intent = new Intent(this, AutoUpdateService.class);        startService(intent);        ....}

@Override    public int onStartCommand(Intent intent,  int flags, int startId) {        updateWeather();        updatePic();        Intent i = new Intent(this, AutoUpdateService.class);        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);        long TriggerAtTime = SystemClock.elapsedRealtime()+8*60*60*1000;//8小时        PendingIntent pi = PendingIntent.getService(this, 0, i, 0);        manager.cancel(pi);        manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, TriggerAtTime, pi);        return super.onStartCommand(intent, flags, startId);    }

完整的代码为：

public class AutoUpdateService extends Service {    public AutoUpdateService() {    }    @Override    public IBinder onBind(Intent intent) {        return null;    }    @Override    public int onStartCommand(Intent intent,  int flags, int startId) {        updateWeather();        updatePic();        Intent i = new Intent(this, AutoUpdateService.class);        AlarmManager manager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);        long TriggerAtTime = SystemClock.elapsedRealtime()+8*60*60*1000;//8小时        PendingIntent pi = PendingIntent.getService(this, 0, i, 0);        manager.cancel(pi);        manager.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, TriggerAtTime, pi);        return super.onStartCommand(intent, flags, startId);    }    //更新图片    private void updatePic() {        String address = "http://guolin.tech/api/bing_pic";        HttpUtil.sendOkHttpRequest(address, new Callback() {            @Override            public void onFailure(Call call, IOException e) {                e.printStackTrace();            }            @Override            public void onResponse(Call call, Response response) throws IOException {                String pic = response.body().string();                SharedPreferences.Editor editor = PreferenceManager.getDefaultSharedPreferences(AutoUpdateService.this).edit();                editor.putString("pic", pic);//将更新的内容存储到缓存中                editor.apply();            }        });    }    //service是发生在界面显示出来以后，所以会有缓存,通过缓存获得weatherId来访问服务器    private void updateWeather() {        SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(AutoUpdateService.this);        final String weatherText = preferences.getString("weather", null);        if (weatherText != null) {            Weather weather = Utility.handleWeatherResponse(weatherText);            String weatherId = weather.basic.weatherId;            String weatherUrl = "https://api.heweather.com/x3/weather?cityid=" + weatherId + "&key=bc0418b57b2d4918819d3974ac1285d9";//            String weatherUrl = "https://api.heweather.com/x3/weather?cityid=" + weatherId + "&key=25b66c67c448456b88bd0f006f9adad9";            HttpUtil.sendOkHttpRequest(weatherUrl, new Callback() {                @Override                public void onFailure(Call call, IOException e) {                    e.printStackTrace();                }                @Override                public void onResponse(Call call, Response response) throws IOException {                    String weathterText = response.body().string();                    Weather weather = Utility.handleWeatherResponse(weatherText);                    if (weather != null && "ok".equals(weather.status)) {                        SharedPreferences.Editor editor = PreferenceManager.getDefaultSharedPreferences(AutoUpdateService.this).edit();                        editor.putString("weather", weatherText);                        editor.apply();                    }                }            });        }    }}

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