java - Android 中的位置为空

Question

我正在尝试获取我的位置。但我所拥有的一切都是零。请看代码:

 public class ListBranchesActivity extends Activity {       

    private double lat, lon;

    private LocationManager lm;
    private Location location;

    private final LocationListener locationListener = new LocationListener() {
        public void onLocationChanged(Location location) {
            lon = location.getLongitude();
            lat = location.getLatitude();
        }

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onProviderEnabled(String provider) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onProviderDisabled(String provider) {
            // TODO Auto-generated method stub

        }
    };

然后在onCreate()中的某个地方:

lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 2000, 10,
                locationListener);
        location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

以下代码返回 NullPointerException:

   Log.w("es09", "coordinates are " + lon + " " + lat +" " +location.getLatitude()+" "+ location.getLongitude());

该代码返回“坐标为 0.0 0.0”

 Log.w("es09", "coordinates are " + lon + " " + lat);

我的 list 权限:

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
   <uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" />
   <uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
   <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
   <uses-permission android:name="android.permission.INTERNET" />
   <uses-permission android:name="android.permission.CALL_PHONE" />
   <uses-permission android:name="android.permission.READ_PHONE_STATE"/>
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
   <uses-permission android:name="android.permission.ACCESS_GPS"/>
   <uses-permission android:name="android.permission.ACCESS_LOCATION"/>
   <uses-permission android:name="android.permission.ACCESS_ASSISTED_GPS"/>

出了什么问题？

Answer 1

问题是您假设您总是能找回位置，但事实并非如此。无法保证位置会返回给您，因此您必须检查是否为空。

使用

lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

不能保证最后一个位置存在，每当您获得一个位置时，您始终应该首先检查以确保它不为空!