Question

我在调用NullPointerException时遇到getSystemService()。我之前检查了一些帖子，但无法弄清楚它失败的原因。

public class GetGyroInfo extends Service implements LocationListener{
    private float mLongAccl;
    private float mLatAccl;

    private static final long MIN_TIME_BW_UPDATES = 100; // 100 millisecond

    //Declaring a location manager
    private LocationManager mLocationManager = null;
    private Location mLocation = null;

    private static final String TAG = "ADAS_GetGyroInfo";

    public void getLocation(Context context){

        //Note: getApplicationContext returns NULL inside this constructor. Reason not clear.

        //Create a registor for location updates
        mLocationManager = (LocationManager)  getSystemService(LOCATION_SERVICE);
...
}

上面的类在以下类中初始化：

    public class ABCService extends Service {

    ...
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        sendStatusBroadcast(true);

        //Registor location service.
        mgetGyroInfo = new GetGyroInfo();
        mgetGyroInfo.getLocation();
}

我尝试了以下代码并且成功了：

mgetGyroInfo.getLocation(getApplicationContext());

所以我的问题是，为什么我必须将ABCService类的上下文传递给GetGyroInfo？为什么我不能在GetGyroInfo本身内部获取上下文？

为什么在调用getSystemService（LOCATION_SERVICE）时遇到NullpointerException

0 个答案: