FusedLocationProviderClient 何时以及如何停止 Looper？

Question

我曾经使用 FusedLocationApi，直到我得知它已被弃用（请参阅下面的参考资料）。实施起来很简单。正如文档所说，您需要将它与 GoogleApiClient 结合使用

LocationServices.FusedLocationApi.requestLocationUpdates(googleApiClient,
                        locationRequest, this);

我最近更改为 FusedLocationProviderClient（请参阅下面的参考资料）按照教程，我能够成功地让 FusedLocationProviderClient 工作

教程：https://github.com/codepath/android_guides/wiki/Retrieving-Location-with-LocationServices-API

// new Google API SDK v11 uses getFusedLocationProviderClient(this)
getFusedLocationProviderClient(this).requestLocationUpdates(mLocationRequest, new LocationCallback() {
      @Override
      public void onLocationResult(LocationResult locationResult) {
         // do work here
         onLocationChanged(locationResult.getLastLocation();
      }
    },
    Looper.myLooper());

我遇到的问题是 Looper 线程。即使应用程序在后台，Looper 线程也会继续运行。我想在应用程序处于后台时暂停位置更新，然后在应用程序处于前台时恢复位置更新。我怎样才能做到这一点？

参考资料：

1. https://developers.google.com/android/reference/com/google/android/gms/location/FusedLocationProviderApi
2. https://developers.google.com/android/reference/com/google/android/gms/location/FusedLocationProviderClient

Answer 1

您只需要在您的活动的onPause() 中调用mFusedLocationClient.removeLocationUpdates(mLocationCallback)。然而，它的意义远不止这些。

在您的主要活动中使用 FusedLocationProviderClient 和 LocationRequest 的成员变量：

import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationResult;

public class MainActivity extends AppCompatActivity
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener {

    FusedLocationProviderClient mFusedLocationClient;
    LocationRequest mLocationRequest;

    //..........

也为 LocationCallback 使用成员变量：

LocationCallback mLocationCallback = new LocationCallback(){
    @Override
    public void onLocationResult(LocationResult locationResult) {
        for (Location location : locationResult.getLocations()) {
            Log.i("MainActivity", "Location: " + location.getLatitude() + " " + location.getLongitude());

        }
    };

};

然后，在onCreate() 中分配mFusedLocationClient：

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

    mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
    requestLocationUpdates();

    //...............
}

那么在onResume()中，如果设置了FusedLocationProviderClient，则使用它。

@Override
public void onResume() {
    if (mFusedLocationClient != null) {
        requestLocationUpdates();
    }
}

public void requestLocationUpdates() {
    mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(120000); // two minute interval
    mLocationRequest.setFastestInterval(120000);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
    if (ContextCompat.checkSelfPermission(this,
            Manifest.permission.ACCESS_FINE_LOCATION)
            == PackageManager.PERMISSION_GRANTED) {
        mFusedLocationClient.requestLocationUpdates(mLocationRequest, mLocationCallback, Looper.myLooper());
    }
}

最后，在onPause() 中，致电removeLocationUpdates()：

@Override
public void onPause() {
    super.onPause();
    if (mFusedLocationClient != null) {
        mFusedLocationClient.removeLocationUpdates(mLocationCallback);
    }
}

Answer 2

获取位置后，只需删除他在上述答案中提到的mFusedLocationClient.removeLocationUpdates。

if (mFusedLocationClient != null) 
        mFusedLocationClient.removeLocationUpdates(mLocationCallback);

Looper 将被称为requestLocationUpdates，直到您将其删除。

在我的问题中，我按照上面提到的那样做了。下面是我的代码。

  mFusedLocationClient.getLastLocation()
                    .addOnSuccessListener(new OnSuccessListener<Location>() {
                        @Override
                        public void onSuccess(Location location) {
                            // GPS location can be null if GPS is switched off
                            if (location != null) {

                                mLocation = location;

                                if (mFusedLocationClient != null) {
                                    mFusedLocationClient.removeLocationUpdates(mLocationCallback);
                                }
                          } else {
                                startLocationUpdates();
                           }
                        }
                    })
                    .addOnFailureListener(new OnFailureListener() {
                        @Override
                        public void onFailure(@NonNull Exception e) {
                            Toast.makeText(HomeActivity.this, "Error trying to get last GPS location", Toast.LENGTH_SHORT).show();
                            e.printStackTrace();
                        }
                    });

下面是我的requestLocationUpdates，所以在位置可用之前我会收到请求。

private void startLocationUpdates() {
        mSettingsClient.checkLocationSettings(mLocationSettingsRequest)
                .addOnSuccessListener(this, new OnSuccessListener<LocationSettingsResponse>() {
                    @Override
                    public void onSuccess(LocationSettingsResponse locationSettingsResponse) {
                        Log.i(TAG, "All location settings are satisfied.");

                        getPackageManager().checkPermission(Manifest.permission.ACCESS_FINE_LOCATION, getPackageName());
                        mFusedLocationClient.requestLocationUpdates(mLocationRequest,
                                mLocationCallback, Looper.myLooper());
                        getLastLocationNewMethod();
                    }
                })
                .addOnFailureListener(this, new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        int statusCode = ((ApiException) e).getStatusCode();
                        switch (statusCode) {
                            case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
                                Log.i(TAG, "Location settings are not satisfied. Attempting to upgrade " +
                                        "location settings ");
                                try {
                                    ResolvableApiException rae = (ResolvableApiException) e;
                                    rae.startResolutionForResult(HomeActivity.this, 0x1);
                                } catch (IntentSender.SendIntentException sie) {
                                    Log.i(TAG, "PendingIntent unable to execute request.");
                                }
                                break;
                            case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
                                String errorMessage = "Location settings are inadequate, and cannot be " +
                                        "fixed here. Fix in Settings.";
                                Log.e(TAG, errorMessage);
                                Toast.makeText(HomeActivity.this, errorMessage, Toast.LENGTH_LONG).show();
                                //  mRequestingLocationUpdates = false;
                        }
                        getLastLocationNewMethod();  // this method is where I can get location. It is calling above method. 
                    }
                });
    }

注意：这里是 GitHub Repo 的更多信息 LINK