Gps android - 获得纬度和经度

Question

你能帮我解决这个问题吗？当我添加地理编码器以通过使用纬度和经度获取城市名称时，应用程序开始崩溃..

    double latitude, longitude;
    private TextView lala;

    LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
    Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    longitude = location.getLongitude();
    latitude = location.getLatitude();
    final LocationListener locationListener = new LocationListener() {
        public void onLocationChanged(Location location) {
            longitude = location.getLongitude();
            latitude = location.getLatitude();
        }

        public void onProviderDisabled(String arg0) {
            // TODO Auto-generated method stub

        }

        public void onProviderEnabled(String arg0) {
            // TODO Auto-generated method stub

        }

        public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
            // TODO Auto-generated method stub

        }
    };

    lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 2000, 10, locationListener);
    lala = (TextView) findViewById(R.id.textView1);

    Geocoder myLocation = new Geocoder(getApplicationContext(), Locale.getDefault());   
    List<Address> myList = null;
    try {
        myList = myLocation.getFromLocation(latitude, longitude, 1);
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }


    lala.setText((CharSequence) myList);

Answer 1

lm.getLastKnownLocation可以返回null，然后尝试getLongitude()您将获得NullPointerException

lala.setText((CharSequence) myList);也可以这样做（抛出异常）因为'myList在这里可以为null（如果Geocoder失败）。

修改 要处理Geocoder中的异常，请考虑以下清单

1. 确保您的纬度和经度不为空
2. 确保-90＆lt; = latitude＆lt; = 90和-180＆lt; =经度＆lt; = 180
3. 确保您有可用的网络连接

<强> EDIT2 改进代码

private TextView lala;

LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

if(location != null) {
    showMyAddress(location);
}

final LocationListener locationListener = new LocationListener() {
    public void onLocationChanged(Location location) {
        showMyAddress(location);
    }

    public void onProviderDisabled(String arg0) {
        // TODO Auto-generated method stub

    }

    public void onProviderEnabled(String arg0) {
        // TODO Auto-generated method stub

    }

    public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
        // TODO Auto-generated method stub

    }
};

lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 2000, 10, locationListener);
lala = (TextView) findViewById(R.id.textView1);



// Also declare a private method

private void showMyAddress(Location location) {
    double latitude = location.getLatitude();
    double longitude = location.getLongitude();
    Geocoder myLocation = new Geocoder(getApplicationContext(), Locale.getDefault());   
    List<Address> myList;
    try {
        myList = myLocation.getFromLocation(latitude, longitude, 1);
        if(myList.size() == 1) {
            lala.setText(myList.get(0).toString());             
        }
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
}

Answer 2

Criteria criteria = new Criteria();
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
String provider = locationManager.getBestProvider(criteria, false);
Location location = locationManager.getLastKnownLocation(provider);
int la = (int) (location.getLatitude() * 1E6);
int lo = (int) (location.getLongitude() * 1E6);