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我正在尝试编写一个实用程序类来包装 Google Play Services FusedLocationProviderClient API 和位置权限请求，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这些样板文件。我遇到的问题是，一旦我开始位置更新，我就无法删除它们。这是我的实用程序类的相关位：

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式（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);
            }
        });

    }

这是日志中的一个示例：

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，我正在正确接收位置更新，但对 stopLocationUpdates() 的调用不起作用。我感觉这与我将新的 LocationCallback 传递给 removeUpdates() 方法这一事实有关，但我不确定替代方案是什么，或者即使有替代方案。这是一个非活动类，我无法将 LocationCallback 完全初始化为 onCreate() 中的成员，然后根据需要传递它。这方面的谷歌文档根本没有多大帮助。无论是因为我缺乏必要的理解来破译它们，还是因为它们不是很好，我不知道，但无论哪种方式，我都被难住了，经过大量搜索，我似乎无法在其他地方找到现有的答案。谢谢。

4

1 回答 1

5

发布我的解决方案作为答案，以防它帮助其他人。

我通过将 LocationCallback 声明为成员变量然后在需要它的每个方法中初始化（或重新初始化）它来使其工作......

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，如果是，请尽早退出。这可以防止启动重复的（因此无法阻止的）位置更新请求。

调用 stopLocationUpdates（以下供参考）方法现在可以正常工作了。

public void stopLocationUpdates(){

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

}
于 2018-08-12T19:50:33.580 回答