java - FusedLocationApi 方法 getLastLocation() 在第一次调用期间始终为 null

Question

正在寻求一些帮助来解决我的应用程序中有关获取当前设备位置的问题。下面是我正在使用的 GPSLocationListener 类。

import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.util.Log;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;



/**
 * This class takes care of capturing the location of the device.
 */
public class GPSLocationListener implements GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener, LocationListener,
        ActivityCompat.OnRequestPermissionsResultCallback {


    protected static final String TAG = "location-updates-sample";

    public static final int LOCATION_RESQUEST = 1;
    /**
     * The desired interval for location updates. Inexact. Updates may be more or less frequent.
     */
    public static final long UPDATE_INTERVAL_IN_MILLISECONDS = 10000;

    /**
     * The fastest rate for active location updates. Exact. Updates will never be more frequent
     * than this value.
     */
    public static final long FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS =
            UPDATE_INTERVAL_IN_MILLISECONDS / 2;

    /**
     * Provides the entry point to Google Play services.
     */
    protected GoogleApiClient mGoogleApiClient;

    /**
     * Stores parameters for requests to the FusedLocationProviderApi.
     */
    protected LocationRequest mLocationRequest;

    /**
     * Represents a geographical location.
     */
    protected Location mCurrentLocation;

    private Activity mActivity;

    public double lat;
    public double lon;

    public GPSLocationListener(Activity activity) {
        this.mActivity = activity;
        // Kick off the process of building a GoogleApiClient and requesting the LocationServices API.
        buildGoogleApiClient();
    }

    /**
     * Builds a GoogleApiClient. Uses the {@code #addApi} method to request the
     * LocationServices API.
     */
    protected synchronized void buildGoogleApiClient() {
        Log.i(TAG, "Building GoogleApiClient");
        mGoogleApiClient = new GoogleApiClient.Builder(mActivity)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        createLocationRequest();
    }

    /**
     * Sets up the location request. Android has two location request settings:
     * {@code ACCESS_COARSE_LOCATION} and {@code ACCESS_FINE_LOCATION}. These settings control
     * the accuracy of the current location. This sample uses ACCESS_FINE_LOCATION, as defined in
     * the AndroidManifest.xml.
     * <p/>
     * When the ACCESS_FINE_LOCATION setting is specified, combined with a fast update
     * interval (5 seconds), the Fused Navigation Provider API returns location updates that are
     * accurate to within a few feet.
     * <p/>
     * These settings are appropriate for mapping applications that show real-time location
     * updates.
     */
    protected void createLocationRequest() {
        mLocationRequest = new LocationRequest();

        // Sets the desired interval for active location updates. This interval is
        // inexact. You may not receive updates at all if no location sources are available, or
        // you may receive them slower than requested. You may also receive updates faster than
        // requested if other applications are requesting location at a faster interval.
        mLocationRequest.setInterval(UPDATE_INTERVAL_IN_MILLISECONDS);

        // Sets the fastest rate for active location updates. This interval is exact, and your
        // application will never receive updates faster than this value.
        mLocationRequest.setFastestInterval(FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS);

        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }

    /**
     * Requests location updates from the FusedLocationApi.
     */
    public void startLocationUpdates(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this.mActivity, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this.mActivity, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this.mActivity, Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED) {
                //return;
            }else {
                try {
                    ActivityCompat.requestPermissions(this.mActivity, new String[]{Manifest.permission.ACCESS_FINE_LOCATION,
                                    Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.INTERNET},
                            LOCATION_RESQUEST);
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
            // If the initial location was never previously requested, we use
            // FusedLocationApi.getLastLocation() to get it. If it was previously requested, we store
            // its value in the Bundle and check for it in onCreate().
            LocationServices.FusedLocationApi.requestLocationUpdates(
                    mGoogleApiClient, mLocationRequest, this);
        }
    }

    /**
     * Removes location updates from the FusedLocationApi.
     */
    protected void stopLocationUpdates() {
        // It is a good practice to remove location requests when the activity is in a paused or
        // stopped state. Doing so helps battery performance and is especially
        // recommended in applications that request frequent location updates.

        // The final argument to {@code requestLocationUpdates()} is a LocationListener
        // (http://developer.android.com/reference/com/google/android/gms/location/LocationListener.html).
        LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
    }

    public void onStart() {
        mGoogleApiClient.connect();
        //createLocationRequest();
        // Within {@code onPause()}, we pause location updates, but leave the
        // connection to GoogleApiClient intact.  Here, we resume receiving
        // location updates if the user has requested them.

    }

    public void onStop() {
        // Stop location updates to save battery, but don't disconnect the GoogleApiClient object.
        if (mGoogleApiClient.isConnected()) {
            stopLocationUpdates();
            mGoogleApiClient.disconnect();
        }

    }

    /**
     * Runs when a GoogleApiClient object successfully connects.
     */
    @Override
    public void onConnected(Bundle connectionHint) {
        Log.i(TAG, "Connected to GoogleApiClient");
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this.mActivity, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this.mActivity, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this.mActivity, Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED) {
                Log.i(TAG, "onConnected: Just empty if statement");
            }else {
                try {
                    ActivityCompat.requestPermissions(this.mActivity, new String[]{Manifest.permission.ACCESS_FINE_LOCATION,
                                    Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.INTERNET},
                            LOCATION_RESQUEST);
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
            mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
            if (mCurrentLocation == null) {
                mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
                Log.i(TAG, "onConnected  " + String.valueOf(mCurrentLocation));
            }
        }
    }

    /**
     * Callback that fires when the location changes.
     */
    @Override
    public void onLocationChanged(Location location) {
        mCurrentLocation = location;
        Log.i(TAG, "onLocationChanged: " + String.valueOf(mCurrentLocation.getLatitude()));
        Log.i(TAG, "onLocationChanged: " + String.valueOf(mCurrentLocation.getLongitude()));
    }

    @Override
    public void onConnectionSuspended(int cause) {
        // The connection to Google Play services was lost for some reason. We call connect() to
        // attempt to re-establish the connection.
        Log.i(TAG, "Connection suspended");
        mGoogleApiClient.connect();
    }

    @Override
    public void onConnectionFailed(ConnectionResult result) {
        // Refer to the javadoc for ConnectionResult to see what error codes might be returned in
        // onConnectionFailed.
        Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = " + result.getErrorCode());
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            mActivity.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
        switch (requestCode){
            case LOCATION_RESQUEST:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                    startLocationUpdates(); // Calling this here is the only place that does not make the app crash
                    getCurrentLocation();
                }else {
                    Log.i(TAG, "onRequestPermissionsResult: Need Permissions");
                    return;
                }
                break;
            default:
                break;
        }
        return;
    }

    public void getCurrentLocation(){
        if (mCurrentLocation != null){
            lat = mCurrentLocation.getLatitude();
            lon = mCurrentLocation.getLongitude();
            Log.i(TAG, "getCurrentLocation(): " + String.valueOf(mCurrentLocation.getLatitude()));
            Log.i(TAG, "getCurrentLocation(): " + String.valueOf(mCurrentLocation.getLongitude()));
        }
    }

    public GoogleApiClient getGoogleApiClient(){
        return mGoogleApiClient;
    }

}

在设置中已启用 GPS 的实际设备上尝试此操作时，我发现了一些奇怪的行为。如果我根本不这样做，请调用 startLocationUpdates() 方法，或者在 onRequestPermissionsResult() 方法中调用它，应用程序会正常启动，并且当我授予设备位置权限时， mCurrentLocation 对象为 null，但不会崩溃。我停止应用程序，然后再次启动，mCurrentLocation 具有我可以在 logcat 中看到的纬度和经度坐标，这正是我首先想要的，但它们只保存任何值，第二次发射后。现在，如果我卸载应用程序并尝试在任何地方调用 startLocationUpdates() 方法，应用程序将在启动时崩溃，并显示错误:

Client must have ACCESS_FINE_LOCATION permission to request PRIORITY_HIGH_ACCURACY locations.

但是我正在检查 onConnected() 方法以及 startLocationUpdates() 方法中的权限，尽管我认为这是不正确的，但这是这是我可以让 Android Studio 不下划线的唯一方法

LocationServices.FusedLocationApi.requestLocationUpdates(
                    mGoogleApiClient, mLocationRequest, this); 

带有权限警告的红色语句。

这是 Activity，我尝试使用 mapItBtnRespond() 方法获取位置更新。

package com.example.bigdaddy.as_built_weldmapper;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

import com.example.bigdaddy.as_built_weldmapper.utilities.BendHelper;
import com.example.bigdaddy.as_built_weldmapper.utilities.GPSLocationListener;

public class SagActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener,
        MajorButtonFragment.OnFragmentInteractionListener, Communicator{

    /* Using this to insert into the Bend Direction field. */
    public static String SAG_DIRECTION = "SAG";

    /* This spinner holds the bend types */
    Spinner mSagBendTypesSpinner;

    /* Using this string to collect what was selected for the spinner type */
    private String mBendTypeSpinnerVal;

    /* All the EditText for the Activity */
    private EditText mSagGpsShotEt;
    private EditText mSagExistingGpsEt;
    private EditText mSagCoverEt;
    private EditText mSagDegreeEt;
    private EditText mSagDistanceFromEt;
    private EditText mSagNotesEt;
    private EditText mSagOccupyIdEt;
    private EditText mSagStationNumEt;

    private GPSLocationListener mGPSLocationListener;

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

        mGPSLocationListener = new GPSLocationListener(SagActivity.this);

        /* checking if the MajorButtonFragment is null */
        if (findViewById(R.id.majorButtonFragment) != null) {
            if (savedInstanceState != null) {
                return;
            }
        }

        /* Referencing the spinner and setting the itemsSelectedListener */
        mSagBendTypesSpinner = (Spinner) findViewById(R.id.bend_types_spinner);
        mSagBendTypesSpinner.setOnItemSelectedListener((AdapterView.OnItemSelectedListener) this);
        /* Create an ArrayAdapter using the string array and a default spinner layout */
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
                R.array.bend_types_array, android.R.layout.simple_spinner_item);
        /* Specify the layout to use when the list of choices appears */
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        /* Apply the adapter to the spinner */
        mSagBendTypesSpinner.setAdapter(adapter);

        /* Referencing and calling all the EditText for the Activity */
        mSagGpsShotEt = (EditText) findViewById(R.id.eTextGpsShotForSag);
        mSagExistingGpsEt = (EditText) findViewById(R.id.eTextExistGradeForSag);
        mSagCoverEt = (EditText) findViewById(R.id.eTextCoverForSag);
        mSagDegreeEt = (EditText) findViewById(R.id.eTextDegreeForSag);
        mSagDistanceFromEt = (EditText) findViewById(R.id.eTextDistanceFromForSag);
        mSagNotesEt = (EditText) findViewById(R.id.eTextNotesForSagActivity);
        mSagOccupyIdEt = (EditText) findViewById(R.id.eTextJointIdSagActivity);
        mSagStationNumEt = (EditText) findViewById(R.id.eTextStationNumSagActivity);
    } /*onCreate() ends here.*/

    @Override
    protected void onStart() {
        super.onStart();
        Log.i("SagActivity", "onStart: ");
        /* Starting the location listener here (GoogleApiClient) */
        if (mGPSLocationListener != null){
            mGPSLocationListener.onStart();
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.i("SagActivity", "onStop: ");
        /* Stopping the location listener here (GoogleApiClient) */
        if (mGPSLocationListener != null){
            mGPSLocationListener.onStop();
        }
    }

    @Override
    public void onLocalVoiceInteractionStopped() {
        super.onLocalVoiceInteractionStopped();
    }

    @Override
    public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
        mBendTypeSpinnerVal = mSagBendTypesSpinner.getSelectedItem().toString();
    }

    @Override
    public void onNothingSelected(AdapterView<?> adapterView) {

    }

    @Override
    public void exitBtnRespond() {

    }

    /**
     * This overridden method comes from the Communicator Interface and is used globally in all
     * Activities that implement it to Store (write) a transaction to the database.
     * The utility class saveAndInsertBend() method is invoked here.
     */
    @Override
    public void storeBtnRespond() {
        BendHelper.saveAndInsertBend(SagActivity.this, SAG_DIRECTION, mBendTypeSpinnerVal, mSagStationNumEt,
                mSagOccupyIdEt, mSagDegreeEt, mSagDistanceFromEt, mSagGpsShotEt, mSagExistingGpsEt,
                mSagCoverEt, mSagNotesEt);
    }

    @Override
    public void mapItBtnRespond() {
        Toast.makeText(this, "MapItBtn clicked in SagActivity",Toast.LENGTH_LONG).show();
        mGPSLocationListener.getCurrentLocation();
        Log.i("SagActivity", "mapItBtnRespond: " + String.valueOf(mGPSLocationListener.lat));
        Log.i("SagActivity", "mapItBtnRespond: " + String.valueOf(mGPSLocationListener.lon));
    }

    @Override
    public void onFragmentInteraction() {

    }

}

我在这里做错了什么？任何帮助将不胜感激，因为我显然对权限感到困惑。非常感谢您的指导。

Answer 1

您在 onConnected() 中请求 FINE_LOCATION 权限，但 onConnected 是在 GPS 连接时调用的。这就是您收到权限错误的原因。

您应该删除此内容:

mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);

来自 onConnected()。将其添加到 getCurrentLocation() 并请求权限:

public void getCurrentLocation(){
        //Request permission here
        mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        if (mCurrentLocation != null){
            lat = mCurrentLocation.getLatitude();
            lon = mCurrentLocation.getLongitude();
            Log.i(TAG, "getCurrentLocation(): " + String.valueOf(mCurrentLocation.getLatitude()));
            Log.i(TAG, "getCurrentLocation(): " + String.valueOf(mCurrentLocation.getLongitude()));
        }
    }

然后在onConnected()中也调用这个方法:

 @Override
    public void onConnected(Bundle connectionHint) {
        Log.i(TAG, "Connected to GoogleApiClient");
            getCurrentLocation();
    }