location始终为null，想让它不为空

Question

为什么location始终为null，怎么样让location不为空?

 public class MainActivity extends Activity {

    public static final int SHOW_LOCATION = 0;

    private TextView positionTextView;

    private LocationManager locationManager;

    private String provider;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        positionTextView = (TextView) findViewById(R.id.position_text_view);
        Toast.makeText(getApplication(), "测试1",
                Toast.LENGTH_LONG).show();

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        // 获取所有可用的位置提供器
        List<String> providerList = locationManager.getProviders(true);
        if (providerList.contains(LocationManager.GPS_PROVIDER)) {
            provider = LocationManager.GPS_PROVIDER;
            Toast.makeText(getApplication(), "测试4",
                    Toast.LENGTH_LONG).show();
        } else if (providerList.contains(LocationManager.NETWORK_PROVIDER)) {
            provider = LocationManager.NETWORK_PROVIDER;
            Toast.makeText(getApplication(), "测试5",
                    Toast.LENGTH_LONG).show();
        } else {
            // 当没有可用的位置提供器时，弹出Toast提示用户
            Toast.makeText(getApplication(), "没有可用的位置提供器",
                    Toast.LENGTH_LONG).show();
            return;
        }
        Toast.makeText(getApplication(), "测试2",
                Toast.LENGTH_LONG).show();
        Location location = locationManager.getLastKnownLocation(provider);
        if (location != null) {
            // 显示当前设备的位置信息
            showLocation(location);
        }
        else
        {
            Toast.makeText(getApplication(), "测试3",
                    Toast.LENGTH_LONG).show();
        }
        locationManager.requestLocationUpdates(provider, 5000, 1,
                locationListener);

     }

    protected void onDestroy() {
        super.onDestroy();
        if (locationManager != null) {
            // 关闭程序时将监听器移除
            locationManager.removeUpdates(locationListener);
        }
    }

    LocationListener locationListener = new LocationListener() {

        @Override
        public void onStatusChanged(String provider, int status, Bundle extras) {
        }

        @Override
        public void onProviderEnabled(String provider) {
        }

        @Override
        public void onProviderDisabled(String provider) {
        }

        @Override
        public void onLocationChanged(Location location) {
            // 更新当前设备的位置信息
            showLocation(location);
        }
    };

    public void showLocation(Location location) {
        String currentPosition="纬度"+location.getLatitude()+"\n"+"经度"+location.getLongitude();
        positionTextView.setText(currentPosition);

    }



}

Answer 1

网络权限什么的，手机中的位置信息打开试试