Question

为什么我不知道，我接受了这个错误。程序在运行之前。但现在我接受了这个错误。谢谢你的帮助......

MenuActivity.java：

final Context context = this;
private LocationManager mLocationManager;
private String PROVİDER = LocationManager.GPS_PROVIDER;
private GoogleMap googleHarita;
Location mLocation;

public class MenuActivity extends FragmentActivity {
    final Context context = this;
    private static final int CAMERA_REQUEST = 1888;

    TextView e_kor, b_kor, acikAdres;
    Fragment harita;
    RadarView mRadarView = null;

    private LocationManager mLocationManager;
    private String PROVİDER = LocationManager.GPS_PROVIDER;
    private GoogleMap googleHarita=null;

    Location mLocation = null;
    TelephonyManager telemamanger;
    String getSimSerialNumber;



    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu);

        // telefon numarası nesnesi
        telemamanger = (TelephonyManager) getSystemService(TELEPHONY_SERVICE);
        e_kor = (TextView) findViewById(R.id.enlmkor);
        b_kor = (TextView) findViewById(R.id.bylmkor);
        acikAdres = (TextView) findViewById(R.id.acikAdres);

        // resim metodu
        mRadarView = (RadarView) findViewById(R.id.radarView);

        // radar çalıştırma metodları
        mRadarView.setShowCircles(true);
        mRadarView.startAnimation();

        // Konum-lokasyon kodları
        mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        final Location mLocation = mLocationManager
                .getLastKnownLocation(PROVİDER);

        if (googleHarita == null) {
            googleHarita = ((SupportMapFragment) getSupportFragmentManager()
                    .findFragmentById(R.id.haritafragment)).getMap();

            if (googleHarita != null) {
                LatLng koordinat = new LatLng(mLocation.getLatitude(),
                        mLocation.getLongitude());
                googleHarita.addMarker(new MarkerOptions().position(koordinat));
                googleHarita.moveCamera(CameraUpdateFactory.newLatLngZoom(
                        koordinat, 10));
            }
        }

        showLocation(mLocation);
        new GetAddressTask().execute(mLocation);

    }

    // Lokasyon işlemleri
    private void showLocation(Location location) {
        if (location == null) {
            Toast.makeText(getApplicationContext(), "Konum Bulunamadı",
                    Toast.LENGTH_SHORT).show();
        } else {
            e_kor.setText(location.getLatitude() + "");
            b_kor.setText(location.getLongitude() + "");
        }
    }   

    @Override
    protected void onPause() {
        super.onPause();
        mLocationManager.removeUpdates(listener);
    }

    @Override
    protected void onResume() {
        super.onResume();
        mLocationManager.requestLocationUpdates(PROVİDER, 0, 0, listener);
    }



    // Konum listener
    private LocationListener listener = new LocationListener() {
        @Override
        public void onLocationChanged(Location location) {
            showLocation(location);
        }

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

        @Override
        public void onProviderEnabled(String provider) {
        }

        @Override
        public void onProviderDisabled(String provider) {
        }
    };

public class GetAddressTask extends AsyncTask<Location, Void, String> {

    @Override
    protected String doInBackground(Location... locations) {
        Geocoder geocoder = new Geocoder(MenuActivity.this);
        Location location = locations[0];
        List<Address> addresses;
        String addrStr = null;
        try {
            addresses = (List<Address>) geocoder.getFromLocation(
                    location.getLatitude(), location.getLongitude(), 5);
            Address addr = addresses.get(0);
            addrStr = addr.getAddressLine(0) + ", " + addr.getAdminArea()
                    + ", " + addr.getCountryName();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return addrStr;
    }

    @Override
    protected void onPostExecute(String result) {
        acikAdres.setText(result);
    }
}

我的日志猫：

11-10 02:20:50.508: E/AndroidRuntime(29376): FATAL EXCEPTION: main
11-10 02:20:50.508: E/AndroidRuntime(29376): Process: com.gpsacilbildirim, PID: 29376
11-10 02:20:50.508: E/AndroidRuntime(29376): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gpsacilbildirim/com.gpsacilbildirim.MainActivity}: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gpsacilbildirim/com.gpsacilbildirim.MenuActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
11-10 02:20:50.508: E/AndroidRuntime(29376):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
11-10 02:20:50.508: E/AndroidRuntime(29376):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
11-10 02:20:50.508: E/AndroidRuntime(29376):    at android.app.ActivityThread.access$900(ActivityThread.java:172)
11-10 02:20:50.508: E/AndroidRuntime(29376):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)

Answer 1

您在logcat中看到的异常指向您活动的onCreate方法中的问题。

有趣的是： java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference。它告诉你，你正在调用getLatitude()的任何对象都是null。

查看方法的主体，只能在这一行：LatLng koordinat = new LatLng(mLocation.getLatitude(), mLocation.getLongitude());。因此，您可以判断崩溃是由mLocation为空引起的。

您正在初始化mLocation，如下所示：mLocationManager.getLastKnownLocation(PROVİDER);。 documentation告诉您如果禁用提供程序，则可能会获得null返回值。

那应该回答“为什么”。现在，您可以考虑为您的应用程序解决此问题的最佳方法。你可以尝试其他提供商吗？如果没有启用任何提供程序，您可以默认使用通用位置吗？是否要显示错误消息，指示用户启用位置服务并提供再次尝试的方法？

Answer 2

getLastKnownLocation（）方法可以并且将返回null。主要问题是它没有向操作系统提示请求新的位置锁定，而只是检查是否存在来自某个其他应用程序位置请求的最后已知位置。如果最近没有其他应用程序发出了位置请求，那么您将获得一个返回给您的空位置。

保证实际获得位置的唯一方法是请求一个，这是通过调用requestLocationUpdates（）完成的。

传递给onLocationChanged（）回调方法的位置不会为null，因为回调只发生在成功的位置锁定上。

尝试调用虚拟方法＆＃39; double android.location.Location.getLatitude（）＆＃39;在null对象引用上

2 个答案: