使用相机意图拍摄照片后的地理标记

Question

我有一个应用程序，使用Android Camera Intent拍照后，我试图将一些gps数据添加到图像的Exif数据中。 但是，当它到达double longitude = location.getLongitude();时，我的应用程序会崩溃。

这是我的代码：

         public void onCreate(Bundle savedInstanceState) 
            {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);


                File folder = new File(Environment.getExternalStorageDirectory() + "/SApp");
                if(folder.exists() == false){
                    folder.mkdirs();
                }         

                setCamera();

            }


    private void setCamera(){
            Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT,Uri.fromFile(new File(Environment.getExternalStorageDirectory(),"/SApp/Attachment" + ".jpg")));
            startActivityForResult(cameraIntent, 1001);
        }

        protected void onActivityResult(int requestCode, int resultCode, Intent data){

            if(resultCode == RESULT_OK){

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

                double longitude = location.getLongitude();
                double latitude = location.getLatitude();
                         File f = new File(Environment.getExternalStorageDirectory(),"/SApp/Attachment" + ".jpg");
                         geoTag(f.getAbsolutePath(),latitude,longitude);

        }
        }


public void geoTag(String filename, double latitude, double longitude){
    ExifInterface exif;

    try {
        exif = new ExifInterface(filename);
        int num1Lat = (int)Math.floor(latitude);
        int num2Lat = (int)Math.floor((latitude - num1Lat) * 60);
        double num3Lat = (latitude - ((double)num1Lat+((double)num2Lat/60))) * 3600000;

        int num1Lon = (int)Math.floor(longitude);
        int num2Lon = (int)Math.floor((longitude - num1Lon) * 60);
        double num3Lon = (longitude - ((double)num1Lon+((double)num2Lon/60))) * 3600000;

        exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE, num1Lat+"/1,"+num2Lat+"/1,"+num3Lat+"/1000");
        exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE, num1Lon+"/1,"+num2Lon+"/1,"+num3Lon+"/1000");


        if (latitude > 0) {
            exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE_REF, "N"); 
        } else {
            exif.setAttribute(ExifInterface.TAG_GPS_LATITUDE_REF, "S");
        }

        if (longitude > 0) {
            exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE_REF, "E");    
        } else {
        exif.setAttribute(ExifInterface.TAG_GPS_LONGITUDE_REF, "W");
        }

        exif.saveAttributes();
    } catch (IOException e) {
        Log.e("PictureActivity", e.getLocalizedMessage());
    } 

    }

错误跟踪：

11-27 10:17:25.865: E/AndroidRuntime(27201): FATAL EXCEPTION: main
11-27 10:17:25.865: E/AndroidRuntime(27201): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1001, result=-1, data=null} to activity {serverbased.app/serverbased.app.ServerAppActivity}: java.lang.NullPointerException
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.ActivityThread.deliverResults(ActivityThread.java:2994)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3037)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.ActivityThread.access$1100(ActivityThread.java:128)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1191)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.os.Looper.loop(Looper.java:137)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.ActivityThread.main(ActivityThread.java:4514)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at java.lang.reflect.Method.invokeNative(Native Method)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at java.lang.reflect.Method.invoke(Method.java:511)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at dalvik.system.NativeStart.main(Native Method)
11-27 10:17:25.865: E/AndroidRuntime(27201): Caused by: java.lang.NullPointerException
11-27 10:17:25.865: E/AndroidRuntime(27201):    at serverbased.app.ServerAppActivity.onActivityResult(ServerAppActivity.java:139)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.Activity.dispatchActivityResult(Activity.java:4654)
11-27 10:17:25.865: E/AndroidRuntime(27201):    at android.app.ActivityThread.deliverResults(ActivityThread.java:2990)
11-27 10:17:25.865: E/AndroidRuntime(27201):    ... 11 more
11-27 10:17:39.794: I/Process(27201): Sending signal. PID: 27201 SIG: 9

任何帮助将不胜感激！

- Nick Chris

---

崩溃的方式是怎样的？是空指针异常吗？我们能看到错误日志吗？ - David M

是的，这是一个空指针异常。 - Nick Chris

所以，如果“location”为空...在调用“location.getLongitude()”之前，您应该检查该条件。至于为什么它为空...？ - David M

我知道它是Null，但我不知道为什么会这样。我不确定它是否会自动打开GPS，所以我甚至打开了我的GPS。所以我不确定为什么它是Null。 - Nick Chris

Answer 1

您正在错误地检索位置。我建议您仔细阅读这篇博客文章：深入了解位置。它将为您提供许多最佳实践。调用getLastKnownLocation不会启动位置提供程序。返回值null表示没有可用的值。您应该使用requestLocationUpdates。请参见下面的代码片段：

LocationManager lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

Criteria fineCriteria.setAccuracy(Criteria.ACCURACY_FINE);
String fineProvider = lm.getBestProvider(fineCriteria, true);

// Start the fine location listener
lm.requestLocationUpdates(fineProvider, 0, 0, locationListenerFine);

private LocationListener locationListenerFine = new LocationListener() {
    public void onLocationChanged(Location location) {

    }

    public void onProviderDisabled(String provider) {
    }

    public void onProviderEnabled(String provider) {
    }

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

- Frohnzie

Answer 2

问题是我使用了LocationManager.GPS_PROVIDER，将其更改为LocationManager.NETWORK_PROVIDER解决了我的问题。

- Nick Chris