使用Google Play服務獲取最后一個已知位置

Question

我一直在瀏覽android開發人員文檔，試圖弄清楚如何獲取當前位置，特別是https://developer.android.com/training/location/retrieve-current.html

當我在android中創建一個新項目並選擇Map模板時，onCreate方法中有代碼，然后還有一個onMapReady方法。

首先，只是為了確認下面的代碼將地圖放在屏幕上？ 如果是這樣，onMapReady只是一種允許操作地圖的方法嗎？

SupportMapFragment mapFragment = (SupportMapFragment) etSupportFragmentManager()
                .findFragmentById(R.id.map); mapFragment.getMapAsync(this);

在文檔中：獲取當前位置信息re：構建到GoogleApiClient，例如

// Create an instance of GoogleAPIClient.
if (mGoogleApiClient == null) {
    mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addConnectionCallbacks(this)
        .addOnConnectionFailedListener(this)
        .addApi(LocationServices.API)
        .build();
}

文檔中指定的其他方法是onStart，onStop和onConnected。 這一切都有意義，但要制作一個非常基本的獲取當前位置應用程序，我仍然使用SupportMapFragment mapFragment =（SupportMapFragment）....從onCreate內生成地圖？ 是否還需要onMapReady函數？ 創建GoogleApiClient實例的最佳位置在哪里？

在隨后的文檔頁面上，還有關於在連接后獲取當前位置設置的信息

 LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder()
     .addLocationRequest(mLocationRequest);

但我只是不確定應該在哪里定義。

最后，在Android Studio的Map模板中，默認類定義為：

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback

但在谷歌文檔中，它被定義為：

公共類MainActivity擴展ActionBarActivity實現ConnectionCallbacks，OnConnectionFailedListener

類延伸到哪個Activity是否重要？

謝謝。

Answer 1

我使用了預先定義的Map Activity.You可以通過它獲取您最后的已知和當前位置。

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener,
        LocationListener {

    private GoogleMap mMap;
    GoogleApiClient mGoogleApiClient;
    Location mLastLocation;
    Marker mCurrLocationMarker;
    LocationRequest mLocationRequest;

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

        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            checkLocationPermission();
        }
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }


    /**
     * Manipulates the map once available.
     * This callback is triggered when the map is ready to be used.
     * This is where we can add markers or lines, add listeners or move the camera. In this case,
     * we just add a marker near Sydney, Australia.
     * If Google Play services is not installed on the device, the user will be prompted to install
     * it inside the SupportMapFragment. This method will only be triggered once the user has
     * installed Google Play services and returned to the app.
     */
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);

        //Initialize Google Play Services
        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (ContextCompat.checkSelfPermission(this,
                    Manifest.permission.ACCESS_FINE_LOCATION)
                    == PackageManager.PERMISSION_GRANTED) {
                buildGoogleApiClient();
                mMap.setMyLocationEnabled(true);
            }
        }
        else {
            buildGoogleApiClient();
            mMap.setMyLocationEnabled(true);
        }
    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        mGoogleApiClient.connect();
    }

    @Override
    public void onConnected(Bundle bundle) {

        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(1000);
        mLocationRequest.setFastestInterval(1000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                == PackageManager.PERMISSION_GRANTED) {
            LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
        }

    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onLocationChanged(Location location) {

            mLastLocation = location;
            if (mCurrLocationMarker != null) {
                mCurrLocationMarker.remove();
            }

            //Place current location marker
            LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
            MarkerOptions markerOptions = new MarkerOptions();
            markerOptions.position(latLng);
            markerOptions.title("Current Position");
            markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
            mCurrLocationMarker = mMap.addMarker(markerOptions);

            //move map camera
            mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
            mMap.animateCamera(CameraUpdateFactory.zoomTo(11));

            //stop location updates
            if (mGoogleApiClient != null) {
                LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
            }

    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {

    }

    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
    public boolean checkLocationPermission(){
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {

            // Asking user if explanation is needed
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.ACCESS_FINE_LOCATION)) {

                // Show an explanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.

                //Prompt the user once explanation has been shown
                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);


            } else {
                // No explanation needed, we can request the permission.
                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);
            }
            return false;
        } else {
            return true;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_LOCATION: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    // permission was granted. Do the
                    // contacts-related task you need to do.
                    if (ContextCompat.checkSelfPermission(this,
                            Manifest.permission.ACCESS_FINE_LOCATION)
                            == PackageManager.PERMISSION_GRANTED) {

                        if (mGoogleApiClient == null) {
                            buildGoogleApiClient();
                        }
                        mMap.setMyLocationEnabled(true);
                    }

                } else {

                    // Permission denied, Disable the functionality that depends on this permission.
                    Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                }
                return;
            }

            // other 'case' lines to check for other permissions this app might request.
            // You can add here other case statements according to your requirement.
        }
    }
}

在Android Manifest中允許網絡狀態權限和位置權限

Answer 2

如果您的要求只是獲取用戶的當前位置，那么您不需要使用MapActivity，您可以依賴LocationServices並請求getLastLocation。以下是為您的目的提供的以下示例代碼。

  // Create an instance of GoogleAPIClient.
if (mGoogleApiClient == null) {
    mGoogleApiClient = new GoogleApiClient.Builder(this)
        .addConnectionCallbacks(this)
        .addOnConnectionFailedListener(this)
        .addApi(LocationServices.API)
        .build();
}

由於您已經實現了GoogleApiClient的監聽器，因此您可以詢問位置，如下面的代碼所示：

     @Override
        public void onConnected(Bundle bundle) {
            Location location = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
            startLocationUpdates();
        }

        protected void startLocationUpdates() {
            Log.d(TAG, "startLocationUpdates--> Start Location Updates");
            LocationServices.FusedLocationApi.requestLocationUpdates(
                    mGoogleApiClient, mLocationRequest, this);
        }

        public void stopLocationUpdates() {
            Log.d(TAG,"stopLocationUpdates--> Stop location updates");
            LocationServices.FusedLocationApi.removeLocationUpdates(
                    mGoogleApiClient, this);
            stopService();
        }

    @Override
    public void onConnectionSuspended(int i) {
        Log.i(TAG, "Connection suspended");
        mGoogleApiClient.connect();
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = " +
                connectionResult.getErrorCode());
    }

    @Override
    public void onLocationChanged(Location location) {
        Log.d(TAG, "onLocationChanged--> Location is " + location.toString());
        mCurrentLocation = location;
    }

此外，如果您想在定期間隔后跟蹤位置，則可以從OnCreate （您創建GoogleApiClient的對象）創建一個這樣的locationRequest對象：

protected void createLocationRequest() {
    Log.d(TAG,"createLocationRequest--> Create Location Request");
    mLocationRequest = new LocationRequest();
    mLocationRequest.setInterval(10 * 1000); //UPDATE_INTERVAL_IN_MS
    mLocationRequest.setFastestInterval(5 * 1000); //FASTEST_UPDATE_INTERVAL_IN_MS
    mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
}

這是startLocation更新方法：

 protected void startLocationUpdates() {
    Log.d(TAG, "startLocationUpdates--> Start Location Updates");
    LocationServices.FusedLocationApi.requestLocationUpdates(
            mGoogleApiClient, mLocationRequest, this);
}

我希望這能回答你的問題，如果能解決你的問題，請將其標記為答案。