如何获取设备位置？

Question

我正在使用openweathermap解析天气信息，它在没有城市的情况下也能正常工作，但是当我尝试获取城市时，它会强制关闭。 我该如何解决？ 一直在寻找时间，但没有运气。

@Override
protected void onPostExecute(Weather weather) {
    super.onPostExecute(weather);

    if (weather.iconData != null && weather.iconData.length > 0) {
        Bitmap img = BitmapFactory.decodeByteArray(weather.iconData, 0, weather.iconData.length);
        imgView.setImageBitmap(img);
    }

    cityText.setText(weather.location.getCity() + "," + weather.location.getCountry());
    condDescr
            .setText(weather.currentCondition.getCondition() + "(" + weather.currentCondition.getDescr() + ")");
    temp.setText("" + Math.round((weather.temperature.getTemp() - 273.15)) + "�C");
    hum.setText("" + weather.currentCondition.getHumidity() + "%");
    press.setText("" + weather.currentCondition.getPressure() + " hPa");
    windSpeed.setText("" + weather.wind.getSpeed() + " mps");
    windDeg.setText("" + weather.wind.getDeg() + "�");

}

}

public class Location implements Serializable {

private float longitude;
private float latitude;
private long sunset;
private long sunrise;
private String country;
private String city;

 ...

public String getCountry() {
return country;
}

public String getCity() {
return city;
}

这是我的日志

FATAL EXCEPTION: main Process: com.survivingwithandroid.weatherapp, PID: 2057 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.myweather.weatherapp.model.Location.getCity()' on a null object reference at com.survivingwithandroid.weatherapp.MainActivity$JSONWeatherTask.onPostExecute(MainActivity.java:114)

UPDATE

JSONWeatherParser.java

        package com.survivingwithandroid.weatherapp;

    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;

    import com.survivingwithandroid.weatherapp.model.Location;
    import com.survivingwithandroid.weatherapp.model.Weather;

    public class JSONWeatherParser {

        public static Weather getWeather(String data) throws JSONException {
            Weather weather = new Weather();

            // We create out JSONObject from the data
            JSONObject jObj = new JSONObject(data);

            // We start extracting the info
            Location loc = new Location();

            JSONObject coordObj = getObject("coord", jObj);
            loc.setLatitude(getFloat("lat", coordObj));
            loc.setLongitude(getFloat("lon", coordObj));

            JSONObject sysObj = getObject("sys", jObj);
            loc.setCountry(getString("country", sysObj));
            loc.setSunrise(getInt("sunrise", sysObj));
            loc.setSunset(getInt("sunset", sysObj));
            loc.setCity(getString("name", jObj));
            weather.location = loc;

            // We get weather info (This is an array)
            JSONArray jArr = jObj.getJSONArray("weather");

            // We use only the first value
            JSONObject JSONWeather = jArr.getJSONObject(0);
            weather.currentCondition.setWeatherId(getInt("id", JSONWeather));
            weather.currentCondition.setDescr(getString("description", JSONWeather));
            weather.currentCondition.setCondition(getString("main", JSONWeather));
            weather.currentCondition.setIcon(getString("icon", JSONWeather));

            JSONObject mainObj = getObject("main", jObj);
            weather.currentCondition.setHumidity(getInt("humidity", mainObj));
            weather.currentCondition.setPressure(getInt("pressure", mainObj));
            weather.temperature.setMaxTemp(getFloat("temp_max", mainObj));
            weather.temperature.setMinTemp(getFloat("temp_min", mainObj));
            weather.temperature.setTemp(getFloat("temp", mainObj));

            // Wind
            JSONObject wObj = getObject("wind", jObj);
            weather.wind.setSpeed(getFloat("speed", wObj));
            weather.wind.setDeg(getFloat("deg", wObj));

            // Clouds
            JSONObject cObj = getObject("clouds", jObj);
            weather.clouds.setPerc(getInt("all", cObj));

            // We download the icon to show

            return weather;
        }

        private static JSONObject getObject(String tagName, JSONObject jObj) throws JSONException {
            JSONObject subObj = jObj.getJSONObject(tagName);
            return subObj;
        }

        private static String getString(String tagName, JSONObject jObj) throws JSONException {
            return jObj.getString(tagName);
        }

        private static float getFloat(String tagName, JSONObject jObj) throws JSONException {
            return (float) jObj.getDouble(tagName);
        }

        private static int getInt(String tagName, JSONObject jObj) throws JSONException {
            return jObj.getInt(tagName);
        }

    }

MainActivity.java

    package com.survivingwithandroid.weatherapp;

import org.json.JSONException;

import com.survivingwithandroid.weatherapp.model.Weather;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends Activity {

    private TextView cityText;
    private TextView condDescr;
    private TextView temp;
    private TextView press;
    private TextView windSpeed;
    private TextView windDeg;

    private TextView hum;
    private ImageView imgView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String city = "London,UK";

        cityText = (TextView) findViewById(R.id.cityText);
        condDescr = (TextView) findViewById(R.id.condDescr);
        temp = (TextView) findViewById(R.id.temp);
        hum = (TextView) findViewById(R.id.hum);
        press = (TextView) findViewById(R.id.press);
        windSpeed = (TextView) findViewById(R.id.windSpeed);
        windDeg = (TextView) findViewById(R.id.windDeg);
        imgView = (ImageView) findViewById(R.id.condIcon);

        JSONWeatherTask task = new JSONWeatherTask();
        task.execute(new String[] { city });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    private class JSONWeatherTask extends AsyncTask<String, Void, Weather> {

        @Override
        protected Weather doInBackground(String... params) {
            Weather weather = new Weather();
            String data = ((new WeatherHttpClient()).getWeatherData(params[0]));

            try {
                weather = JSONWeatherParser.getWeather(data);

                // Let's retrieve the icon
                weather.iconData = ((new WeatherHttpClient()).getImage(weather.currentCondition.getIcon()));

            } catch (JSONException e) {
                e.printStackTrace();
            }
            return weather;

        }

        @Override
        protected void onPostExecute(Weather weather) {
            super.onPostExecute(weather);

            if (weather.iconData != null && weather.iconData.length > 0) {
                Bitmap img = BitmapFactory.decodeByteArray(weather.iconData, 0, weather.iconData.length);
                imgView.setImageBitmap(img);
            }

            cityText.setText(weather.location.getCity() + "," + weather.location.getCountry());
            condDescr
                    .setText(weather.currentCondition.getCondition() + "(" + weather.currentCondition.getDescr() + ")");
            temp.setText("" + Math.round((weather.temperature.getTemp() - 273.15)) + "�C");
            hum.setText("" + weather.currentCondition.getHumidity() + "%");
            press.setText("" + weather.currentCondition.getPressure() + " hPa");
            windSpeed.setText("" + weather.wind.getSpeed() + " mps");
            windDeg.setText("" + weather.wind.getDeg() + "�");

        }

    }
}

WeatherHttpClient.java

    package com.survivingwithandroid.weatherapp;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class WeatherHttpClient {

    private static String BASE_URL = "http://api.openweathermap.org/data/2.5/weather?q=";
    private static String IMG_URL = "http://openweathermap.org/img/w/";

    public String getWeatherData(String location) {
        HttpURLConnection con = null;
        InputStream is = null;

        try {
            con = (HttpURLConnection) (new URL(BASE_URL + location)).openConnection();
            con.setRequestMethod("GET");
            con.setDoInput(true);
            con.setDoOutput(true);
            con.connect();

            // Let's read the response
            StringBuffer buffer = new StringBuffer();
            is = con.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            String line = null;
            while ((line = br.readLine()) != null)
                buffer.append(line + "\r\n");

            is.close();
            con.disconnect();
            return buffer.toString();
        } catch (Throwable t) {
            t.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (Throwable t) {
            }
            try {
                con.disconnect();
            } catch (Throwable t) {
            }
        }

        return null;

    }

    public byte[] getImage(String code) {
        HttpURLConnection con = null;
        InputStream is = null;
        try {
            con = (HttpURLConnection) (new URL(IMG_URL + code)).openConnection();
            con.setRequestMethod("GET");
            con.setDoInput(true);
            con.setDoOutput(true);
            con.connect();

            // Let's read the response
            is = con.getInputStream();
            byte[] buffer = new byte[1024];
            ByteArrayOutputStream baos = new ByteArrayOutputStream();

            while (is.read(buffer) != -1)
                baos.write(buffer);

            return baos.toByteArray();
        } catch (Throwable t) {
            t.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (Throwable t) {
            }
            try {
                con.disconnect();
            } catch (Throwable t) {
            }
        }

        return null;

    }
}

Location.java

    package com.survivingwithandroid.weatherapp.model;

import java.io.Serializable;

public class Location implements Serializable {

    private float longitude;
    private float latitude;
    private long sunset;
    private long sunrise;
    private String country;
    private String city;

    public float getLongitude() {
        return longitude;
    }

    public void setLongitude(float longitude) {
        this.longitude = longitude;
    }

    public float getLatitude() {
        return latitude;
    }

    public void setLatitude(float latitude) {
        this.latitude = latitude;
    }

    public long getSunset() {
        return sunset;
    }

    public void setSunset(long sunset) {
        this.sunset = sunset;
    }

    public long getSunrise() {
        return sunrise;
    }

    public void setSunrise(long sunrise) {
        this.sunrise = sunrise;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

}

Weather.java

    package com.survivingwithandroid.weatherapp.model;

public class Weather {

    public Location location;
    public CurrentCondition currentCondition = new CurrentCondition();
    public Temperature temperature = new Temperature();
    public Wind wind = new Wind();
    public Rain rain = new Rain();
    public Snow snow = new Snow();
    public Clouds clouds = new Clouds();

    public byte[] iconData;

    public class CurrentCondition {
        private int weatherId;
        private String condition;
        private String descr;
        private String icon;

        private float pressure;
        private float humidity;

        public int getWeatherId() {
            return weatherId;
        }

        public void setWeatherId(int weatherId) {
            this.weatherId = weatherId;
        }

        public String getCondition() {
            return condition;
        }

        public void setCondition(String condition) {
            this.condition = condition;
        }

        public String getDescr() {
            return descr;
        }

        public void setDescr(String descr) {
            this.descr = descr;
        }

        public String getIcon() {
            return icon;
        }

        public void setIcon(String icon) {
            this.icon = icon;
        }

        public float getPressure() {
            return pressure;
        }

        public void setPressure(float pressure) {
            this.pressure = pressure;
        }

        public float getHumidity() {
            return humidity;
        }

        public void setHumidity(float humidity) {
            this.humidity = humidity;
        }

    }

    public class Temperature {
        private float temp;
        private float minTemp;
        private float maxTemp;

        public float getTemp() {
            return temp;
        }

        public void setTemp(float temp) {
            this.temp = temp;
        }

        public float getMinTemp() {
            return minTemp;
        }

        public void setMinTemp(float minTemp) {
            this.minTemp = minTemp;
        }

        public float getMaxTemp() {
            return maxTemp;
        }

        public void setMaxTemp(float maxTemp) {
            this.maxTemp = maxTemp;
        }

    }

    public class Wind {
        private float speed;
        private float deg;

        public float getSpeed() {
            return speed;
        }

        public void setSpeed(float speed) {
            this.speed = speed;
        }

        public float getDeg() {
            return deg;
        }

        public void setDeg(float deg) {
            this.deg = deg;
        }

    }

    public class Rain {
        private String time;
        private float ammount;

        public String getTime() {
            return time;
        }

        public void setTime(String time) {
            this.time = time;
        }

        public float getAmmount() {
            return ammount;
        }

        public void setAmmount(float ammount) {
            this.ammount = ammount;
        }

    }

    public class Snow {
        private String time;
        private float ammount;

        public String getTime() {
            return time;
        }

        public void setTime(String time) {
            this.time = time;
        }

        public float getAmmount() {
            return ammount;
        }

        public void setAmmount(float ammount) {
            this.ammount = ammount;
        }

    }

    public class Clouds {
        private int perc;

        public int getPerc() {
            return perc;
        }

        public void setPerc(int perc) {
            this.perc = perc;
        }

    }

}

Answer 1

请找到用于使用LocationManager获取位置的附件代码。

private GoogleApiClient mGoogleApiClient;
        private Context mContext;

    @SuppressWarnings({"MissingPermission"})
        public void getLocation(Context context) {
            mContext = context;
            LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

            if (locationManager != null) {
                // getting GPS status
                boolean isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

                // getting network status
                boolean isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

                if (!isGPSEnabled && !isNetworkEnabled) {
                    //Show message alert for gps enable 
                } else {
                    mGoogleApiClient = new GoogleApiClient.Builder(context)
                            .addConnectionCallbacks(this)
                            .addOnConnectionFailedListener(this)
                            .addApi(LocationServices.API)
                            .build();
                    mGoogleApiClient.connect();
                }
            }
        }

之后，您将在onConnected方法上获得回调，并从那里获取位置

@Override
public void onConnected(@Nullable Bundle bundle) {
    Location location = LocationServices.FusedLocationApi.getLastLocation(
            mGoogleApiClient);
    if (location != null) {
        double lat= location.getLatitude();
       double lang= location.getLongitude());
    } else {
        //No location found message
    }
    mGoogleApiClient.disconnect();
}