android - 无法获取所有用户位置android

Question

我无法理解整个获取用户位置的过程。我遵循了 LocationManager 的教程。它从 GPS 提供商处获取最后已知位置。据我所知，有些用户没有最后知道的位置，它返回 NULL。

我假设如果 NULL 将使用 GPS 并尝试获取用户位置，则下面的代码会这样。但事实并非如此。如何强制 android 检索用户位置？而不是只显示我的 NULL 消息而不起作用？

setContentView(R.layout.beer_location_list);

        String title = "Nearby Breweries";
        TextView topTitle = (TextView) findViewById(R.id.beerLocationTitle);
        topTitle.setText(title);

        //get user location

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

        if(location != null)
        {
            double longitude = location.getLongitude();
            double latitude = location.getLatitude();

            //construct url
            String url = "myURl";

            Log.d("urlTest",url);

            //async task goes here
            new GetNearbyBreweries(this).execute(url);
        }

        else{
            //pop toast saying cant get location
            Toast.makeText(getApplicationContext(), "Can not get your location at this time", Toast.LENGTH_LONG).show();

        }

更新:

在查看了一些回复之后，为什么我不能做这样的事情来获取用户每次打开此 Activity 时的位置:

  final LocationManager manager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
        Criteria criteria = new Criteria();
        criteria.setAccuracy(Criteria.ACCURACY_COARSE);
        criteria.setAltitudeRequired(false);
        criteria.setSpeedRequired(false);
        criteria.setBearingRequired(false);
        criteria.setCostAllowed(false);

        LocationListener listener = new LocationListener();


        manager.requestSingleUpdate(criteria, listener, null);

我用

覆盖了位置监听器

@Override
    public void onLocationChanged(Location lastKnownLocation) {
        if (lastKnownLocation != null) {
            // whatever needs to be done
        }
    }

但我收到错误:LocationListener is abstract cannot be instantiated on the line new LocationListener();

Answer 1

通过注册一个LocationListener 并使用requestSingleUpdate 来请求更新当前位置，从而为您的位置请求一次更新。我假设您拥有应用程序 list 中列出的正确权限。请注意，您可能不会收到更新，尤其是因为较新的 Android 版本允许用户禁止应用访问位置信息。

LocationManager manager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_COARSE);
criteria.setAltitudeRequired(false);
criteria.setSpeedRequired(false);
criteria.setBearingRequired(false);
criteria.setCostAllowed(false);

LocationListener listener = new LocationListener() {
        @Override
        public void onLocationChanged(Location lastKnownLocation) {
            if (lastKnownLocation != null) {
               // whatever needs to be done
            }
        }

manager.requestSingleUpdate(criteria, listener, null);