Question

我遇到了解决当前位置问题的问题，其中LocationManager给出了错误：

我添加了这段代码，但它需要返回值。我应该只返回null或..？

以下是我的位置代码：

public class GPSService extends Service implements LocationListener {

// saving the context for later use
private final Context mContext;

// if GPS is enabled
boolean isGPSEnabled = false;
// if Network is enabled
boolean isNetworkEnabled = false;
// if Location co-ordinates are available using GPS or Network
public boolean isLocationAvailable = false;

// Location and co-ordinates coordinates
Location mLocation;
double mLatitude;
double mLongitude;

// Minimum time fluctuation for next update (in milliseconds)
private static final long TIME = 30000;
// Minimum distance fluctuation for next update (in meters)
private static final long DISTANCE = 20;

// Declaring a Location Manager
protected LocationManager mLocationManager;

public GPSService(Context context) {
    this.mContext = context;
    mLocationManager = (LocationManager) mContext
            .getSystemService(LOCATION_SERVICE);
}

/**
 * Returs the Location
 *
 * @return Location or null if no location is found
 */
public Location getLocation() {
    try {

        // If reaching here means, we were not able to get location neither
        // from GPS not Network,
        if (!isGPSEnabled) {
            // so asking user to open GPS
            askUserToOpenGPS();
        }

        mLocationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // Getting GPS status
        isGPSEnabled = mLocationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);

if ( Build.VERSION.SDK_INT >= 23 &&
                ContextCompat.checkSelfPermission( getApplicationContext(), android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission( getApplicationContext(), android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return  ;


        // If GPS enabled, get latitude/longitude using GPS Services
        if (isGPSEnabled) {
            mLocationManager.requestLocationUpdates(
                    LocationManager.GPS_PROVIDER, TIME, DISTANCE, this);
            if (mLocationManager != null) {
                mLocation = mLocationManager
                        .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                if (mLocation != null) {
                    mLatitude = mLocation.getLatitude();
                    mLongitude = mLocation.getLongitude();
                    isLocationAvailable = true; // setting a flag that
                    // location is available
                    return mLocation;
                }
            }
        }

        // If we are reaching this part, it means GPS was not able to fetch
        // any location
        // Getting network status
        isNetworkEnabled = mLocationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (isNetworkEnabled) {
            mLocationManager.requestLocationUpdates(
                    LocationManager.NETWORK_PROVIDER, TIME, DISTANCE, this);
            if (mLocationManager != null) {
                mLocation = mLocationManager
                        .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                if (mLocation != null) {
                    mLatitude = mLocation.getLatitude();
                    mLongitude = mLocation.getLongitude();
                    isLocationAvailable = true; // setting a flag that
                    // location is available
                    return mLocation;
                }
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }
    // if reaching here means, location was not available, so setting the
    // flag as false
    isLocationAvailable = false;
    return null;
    }
}

/**
 * Gives you complete address of the location
 *
 * @return complete address in String
 */
public String getLocationAddress() {

    if (isLocationAvailable) {

        Geocoder geocoder = new Geocoder(mContext, Locale.getDefault());
        // Get the current location from the input parameter list
        // Create a list to contain the result address
        List<Address> addresses = null;
        try {
            /*
             * Return 1 address.
             */
            addresses = geocoder.getFromLocation(mLatitude, mLongitude, 1);
        } catch (IOException e1) {
            e1.printStackTrace();
            return ("IO Exception trying to get address:" + e1);
        } catch (IllegalArgumentException e2) {
            // Error message to post in the log
            String errorString = "Illegal arguments "
                    + Double.toString(mLatitude) + " , "
                    + Double.toString(mLongitude)
                    + " passed to address service";
            e2.printStackTrace();
            return errorString;
        }
        // If the reverse geocode returned an address
        if (addresses != null && addresses.size() > 0) {
            // Get the first address
            Address address = addresses.get(0);
            /*
             * Format the first line of address (if available), city, and
             * country name.
             */
            String addressText = String.format(
                    "%s, %s, %s",
                    // If there's a street address, add it
                    address.getMaxAddressLineIndex() > 0 ? address
                            .getAddressLine(0) : "",
                    // Locality is usually a city
                    address.getLocality(),
                    // The country of the address
                    address.getCountryName());
            // Return the text
            return addressText;
        } else {
            return "No address found by the service: Note to the developers, If no address is found by google itself, there is nothing you can do about it.";
        }
    } else {
        return "Location Not available";
    }

}



/**
 * get latitude
 *
 * @return latitude in double
 */
public double getLatitude() {
    if (mLocation != null) {
        mLatitude = mLocation.getLatitude();
    }
    return mLatitude;
}

/**
 * get longitude
 *
 * @return longitude in double
 */
public double getLongitude() {
    if (mLocation != null) {
        mLongitude = mLocation.getLongitude();
    }
    return mLongitude;
}

/**
 * close GPS to save battery
 */
public void closeGPS() {
    if (mLocationManager != null) {
        try {
            mLocationManager.removeUpdates(GPSService.this);
        } catch (SecurityException e) {
            Log.e("PERMISSION_EXCEPTION", "PERMISSION_NOT_GRANTED");
        }
    }
}

/**
 * show settings to open GPS
 */
public void askUserToOpenGPS() {
    AlertDialog.Builder mAlertDialog = new AlertDialog.Builder(mContext);

    // Setting Dialog Title
    mAlertDialog.setTitle("Location not available, Open GPS?")
            .setMessage("Activate GPS to use use location services?")
            .setPositiveButton("Open Settings", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                    mContext.startActivity(intent);
                }
            })
            .setNegativeButton("Cancel",new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    dialog.cancel();
                }
            }).show();
}

/**
 * Updating the location when location changes
 */
@Override
public void onLocationChanged(Location location) {
    mLatitude = location.getLatitude();
    mLongitude = location.getLongitude();
}

@Override
public void onProviderDisabled(String provider) {
}

@Override
public void onProviderEnabled(String provider) {
}

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

@Override
public IBinder onBind(Intent arg0) {
    return null;
}

}

我也在Android Manifest中添加了这些代码：

 <uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

Answer 1

在清单文件中指定以下权限

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

并检查上面的API 23的运行时权限

if ( Build.VERSION.SDK_INT >= 23 &&
         ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED &&
         ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        return  null;
    }

Answer 2

尝试使用此代码检查位置权限并要求相同。

int permissionCheck = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.ACCESS_FINE_LOCATION);
            int permissionCheck1 = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.ACCESS_COARSE_LOCATION);
            if (permissionCheck == PackageManager.PERMISSION_GRANTED && permissionCheck1 == PackageManager.PERMISSION_GRANTED) {
                startService(new Intent(MainActivity.this, TrackingService.class));
                locationRelatedServices();
            } else {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION, android.Manifest.permission.ACCESS_FINE_LOCATION}, PermissionInts.LOCATION_CODE);
            }

用户授予权限后，您可以使用此代码运行项目：

public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode) {
        case PermissionInts.LOCATION_CODE:
                    locationRelatedServices();
            }
            break;

}

Answer 3

您的方法会返回Location个对象，当您无法获取该位置时，您需要返回null（未授予权限时）。

使用

return null;而不是return;

Answer 4

使用此源代码

//启用Marshmallow的位置权限

public void getPermissionLocation(){
    // 1) Use the support library version ContextCompat.checkSelfPermission(...) to avoid
    // checking the build version since Context.checkSelfPermission(...) is only available
    // in Marshmallow
    // 2) Always check for permission (even if permission has already been granted)
    // since the user can revoke permissions at any time through Settings
    if (ContextCompat.checkSelfPermission(PrimecardSplashscreen.this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(PrimecardSplashscreen.this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {

        // The permission is NOT already granted.
        // Check if the user has been asked about this permission already and denied
        // it. If so, we want to give more explanation about why the permission is needed.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                if (shouldShowRequestPermissionRationale(
                        Manifest.permission.ACCESS_FINE_LOCATION)) {
                    // Show our own UI to explain to the user why we need to read the contacts
                    // before actually requesting the permission and showing the default UI
                }
            }
        }

        // Fire off an async request to actually get the permission
        // This will show the standard permission request dialog UI
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                    AppData.READ_LOCATION_PERMISSIONS_REQUEST);
        }
    }

}


@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {


    // Make sure it's our original ACCESS_FINE_LOCATION request
    if (requestCode == AppData.READ_LOCATION_PERMISSIONS_REQUEST) {
        if (grantResults.length == 1 &&
                grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(PrimecardSplashscreen.this, "Read Location permission granted", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(PrimecardSplashscreen.this, "Read Location permission denied", Toast.LENGTH_SHORT).show();
        }
    } else {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}

如何解决呼叫需求权限[Android]

4 个答案: