java - 位置值返回 null android

Question

我正在尝试获取用户的位置，我有这个方法

public Location getCurrentLocation() {
    LocationManager locManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    String provider = locManager.getBestProvider(criteria, true);
    Location location = locManager.getLastKnownLocation(provider);
    return location; 
}

我有另一种方法，可以根据该方法中的location变量的纬度和经度将圆形对象居中

private void loadMapResources() {
     userLocation = getCurrentLocation();
     //DRAW CIRCLE HERE
     if(userRadius != 0){
         Circle radiusCircle = googleMap.addCircle(new CircleOptions()
        .center(new LatLng(userLocation.getLatitude(), userLocation.getLongitude()))
        .radius(userRadius)
        .strokeWidth(4)
        .strokeColor(Color.parseColor("#FF6699"))
        .fillColor(Color.parseColor("#66F3F3F3"))
      );
         //SHOW USER ICON AT CURRENT LOCATION
         BitmapDescriptor userIcon = BitmapDescriptorFactory.fromResource(R.drawable.ic_user);
         googleMap.addMarker(new MarkerOptions()
                .title("YOU ARE HERE")
                .icon(userIcon)
                .position(new LatLng(userLocation.getLatitude(), userLocation.getLongitude()))
                );
     }
}

现在，此代码之前可以在带或不带 GPS 的设备上运行。谁能告诉我为什么 userLocation 抛出 NullPointerException ？

Answer 1

请记住，getLastKnownLocation 有时可能返回 null(例如，如果提供商当前已禁用或没有最后的已知位置)，因此您应该始终检查此方法的结果:

Location location = locManager.getLastKnownLocation(provider);
if (location == null){
    //handle this case
    //return location with some default coordinates, for example
}
return location;