Question

我正试图编写一个实用程序类来包装Google Play服务FusedLocationProviderClient API和位置许可请求，因为每次我想向应用程序添加位置功能时，我都厌倦了编写所有样板文件。我遇到的问题是，启动位置更新后，我将无法删除它们。这是我的实用程序类的相关内容：

public class UserLocationUtility extends LocationCallback
{
    // Hold a WeakReference to the host activity (allows it to be garbage-collected to prevent possible memory leak)
    private final WeakReference<Activity> weakActivity;
    // Debug tag
    private static final String TAG = "UserLocationUtility";


    public static class RequestCodes
    {
        static final int CURRENT_LOCATION_ONE_TIME = 0;
        static final int CURRENT_LOCATION_UPDATES = 1;
        static final int LAST_KNOWN_LOCATION = 2;
        static final int SMART_LOCATION = 3;
    }


    private FusedLocationProviderClient mLocationClient;
    private Context mContext;
    private LocationRequest mLocationRequest;


    /* Constructor */
    UserLocationUtility(Activity activity){
        // assign the activity to the weak reference
        this.weakActivity = new WeakReference<>(activity);

        // Hold a reference to the Application Context
        this.mContext = activity.getApplicationContext();

        // Instantiate our location client
        this.mLocationClient = LocationServices.getFusedLocationProviderClient(mContext);

        // Set up the default LocationRequest parameters
        this.mLocationRequest = new LocationRequest();
        setLocationRequestParams(2000, 500, LocationRequest.PRIORITY_HIGH_ACCURACY);
                                // Sets up the LocationRequest with an update interval of 30 seconds, a fastest
                                // update interval cap of 5 seconds and using balanced power accuracy priority.
    } /* Note: values for testing only. Will be dialed back for better power management when testing complete */


    /* Stripped out other methods for brevity */


    @SuppressLint("MissingPermission")
    public void getCurrentLocationOneTime(final UserLocationCallback callback){

        mLocationClient.requestLocationUpdates(mLocationRequest, new LocationCallback()
        {
            @Override
            public void onLocationResult(LocationResult locationResult){
                if (locationResult == null){
                    callback.onFailedRequest("getCurrentLocationOneTime(): Request failed: returned null");
                    return;
                }

                callback.onLocationResult(locationResult.getLastLocation());
                stopLocationUpdates(); /* Stopping location updates here just for testing (NOT WORKING!!) */ 

            }
        }, null);

    }


    public void stopLocationUpdates(){

        mLocationClient.removeLocationUpdates(new LocationCallback(){});
        Log.i(TAG, "stopLocationUpdates(): Location updates removed");

    }

}

这是我尝试使用它的方法（来自MainActivity）：

UserLocationUtility locationUtility;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    locationUtility = new UserLocationUtility(this);

    if (locationUtility.checkPermissionGranted()){
        Log.i(TAG, "Permissions are granted.");
        getLocationUpdates();
    } else {
        Log.i(TAG, "Permissions are not granted. Attempting to request...");
        locationUtility.requestPermissions(UserLocationUtility.RequestCodes.CURRENT_LOCATION_UPDATES);
    }


}

    public void getLocationUpdates(){

        locationUtility.getCurrentLocationOneTime(new UserLocationCallback() {
            @Override
            public void onLocationResult(Location location) {
                Log.i(TAG, "getLocationUpdates result: " + location.toString());
            }

            @Override
            public void onFailedRequest(String result) {
                Log.e(TAG, "LocationUpdates result: " + result);
            }
        });

    }

这是日志中的示例：

I/MainActivity: getLocationUpdates result: Location[fused 34.421998,-125.084000 hAcc=731 et=+2h10m52s694ms vAcc=??? sAcc=??? bAcc=???]
I/UserLocationUtility: stopLocationUpdates(): Location updates removed
I/MainActivity: getLocationUpdates result: Location[fused 34.421998,-125.084000 hAcc=739 et=+2h10m57s697ms vAcc=??? sAcc=??? bAcc=???]
I/UserLocationUtility: stopLocationUpdates(): Location updates removed
I/MainActivity: getLocationUpdates result: Location[fused 34.421998,-125.084000 hAcc=763 et=+2h11m5s723ms vAcc=??? sAcc=??? bAcc=???]
I/UserLocationUtility: stopLocationUpdates(): Location updates removed
etc...

如您所见，我正确接收到位置更新，但对stopLocationUpdates（）的调用无法正常工作。我感觉这与我将一个新的LocationCallback传递给removeUpdates（）方法有关，但是我不确定替代方案是什么，或者即使有替代方案也不确定。这是一个非活动类，我无法完全将LocationCallback初始化为onCreate（）中的成员，然后根据需要传递给它。谷歌文档对此没有多大帮助。那是因为我缺乏解读它们的必要理解，还是因为它们不是很好，我不知道，但是无论如何，我很沮丧，经过反复搜索，似乎无法在其他地方找到现有的答案。谢谢。

Answer 1

发布我的解决方案作为答案，以防其他人受益。

我通过将LocationCallback声明为成员变量，然后在需要它的每种方法中对其进行初始化（或重新初始化）来实现它...

public void getCurrentLocationUpdates(final UserLocationCallback callback){
        if (mIsReceivingUpdates){
            callback.onFailedRequest("Device is already receiving updates");
            return;
        }

        // Set up the LocationCallback for the request
        mLocationCallback = new LocationCallback()
        {
            @Override
            public void onLocationResult(LocationResult locationResult){
                if (locationResult != null){
                    callback.onLocationResult(locationResult.getLastLocation());
                } else {
                    callback.onFailedRequest("Location request returned null");
                }
            }
        };

        // Start the request
        mLocationClient.requestLocationUpdates(mLocationRequest, mLocationCallback, null);
        // Update the request state flag
        mIsReceivingUpdates = true;
    }

我在方法开始时检查是否已经收到位置更新，如果有，请提早离开。这样可以防止发起重复的（因此不可阻挡的）位置更新请求。

现在，调用stopLocationUpdates（下面用作参考）方法可以正常工作。

public void stopLocationUpdates(){

    mLocationClient.removeLocationUpdates(mLocationCallback);
    mIsReceivingUpdates = false;
    Log.i(TAG, "Location updates removed");

}

如何从非活动类中删除FusedlocationProviderClient位置更新

1 个答案: