onLocChange這是什麼？ onLocationChanged是一種重寫方法。您可以使用它。
注：你已經創建了自己的onLocChange方法，並調用它onMapReady所以它被稱爲只在首先時間。然後onLocChange不會被調用。但如果您使用onLocationChanged覆蓋方法，則每當位置變化時都會調用它！
是
刪除裏面首先，如果塊它涵蓋了所有的代碼，並只能在地圖上爲空，當映射爲null，不存在添加標記的點，保持它離開..或用它像下面
if(map==null){
//map null
} else {
// add code for markers
}
如果你使用上面塊，應與其他部分去
if (currLocationMarker != null) {
// you already have a marker so when location changes you remove it and add a new one thats why you need this
currLocationMarker.remove();
}
latLng = new LatLng(location.getLatitude(), location.getLongitude());
MarkerOptions markerOptions = new MarkerOptions(); // just added to clear thingsyou you can add this where instance creates only once
markerOptions.position(latLng);
markerOptions.title("Current Position");
markerOptions.icon(iconForVehicleMarker);
currLocationMarker = mGoogleMap.addMarker(markerOptions);
想要的一切一個完整的例子，你需要知道（additional）？看到onMapReadyonLocationChaged和相關方法在這裏
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.PendingResult;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.location.places.PlaceLikelihood;
import com.google.android.gms.location.places.PlaceLikelihoodBuffer;
import com.google.android.gms.location.places.Places;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
/**
* An activity that displays a map showing places around the device's current location.
*/
public class MapsActivityCurrentPlaces extends AppCompatActivity implements
OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener {
private static final String TAG = MapsActivityCurrentPlaces.class.getSimpleName();
private GoogleMap mMap;
private CameraPosition mCameraPosition;
// The entry point to Google Play services, used by the Places API and Fused Location Provider.
private GoogleApiClient mGoogleApiClient;
// A request object to store parameters for requests to the FusedLocationProviderApi.
private LocationRequest mLocationRequest;
// The desired interval for location updates. Inexact. Updates may be more or less frequent.
private 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.
private static final long FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS =
UPDATE_INTERVAL_IN_MILLISECONDS/2;
// A default location (Sydney, Australia) and default zoom to use when location permission is
// not granted.
private final LatLng mDefaultLocation = new LatLng(-33.8523341, 151.2106085);
private static final int DEFAULT_ZOOM = 15;
private static final int PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION = 1;
private boolean mLocationPermissionGranted;
// The geographical location where the device is currently located.
private Location mCurrentLocation;
// Keys for storing activity state.
private static final String KEY_CAMERA_POSITION = "camera_position";
private static final String KEY_LOCATION = "location";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Retrieve location and camera position from saved instance state.
if (savedInstanceState != null) {
mCurrentLocation = savedInstanceState.getParcelable(KEY_LOCATION);
mCameraPosition = savedInstanceState.getParcelable(KEY_CAMERA_POSITION);
}
// Retrieve the content view that renders the map.
setContentView(R.layout.activity_maps);
// Build the Play services client for use by the Fused Location Provider and the Places API.
buildGoogleApiClient();
mGoogleApiClient.connect();
}
/**
* Get the device location and nearby places when the activity is restored after a pause.
*/
@Override
protected void onResume() {
super.onResume();
if (mGoogleApiClient.isConnected()) {
getDeviceLocation();
}
updateMarkers();
}
/**
* Stop location updates when the activity is no longer in focus, to reduce battery consumption.
*/
@Override
protected void onPause() {
super.onPause();
if (mGoogleApiClient.isConnected()) {
LocationServices.FusedLocationApi.removeLocationUpdates(
mGoogleApiClient, this);
}
}
/**
* Saves the state of the map when the activity is paused.
*/
@Override
protected void onSaveInstanceState(Bundle outState) {
if (mMap != null) {
outState.putParcelable(KEY_CAMERA_POSITION, mMap.getCameraPosition());
outState.putParcelable(KEY_LOCATION, mCurrentLocation);
super.onSaveInstanceState(outState);
}
}
/**
* Gets the device's current location and builds the map
* when the Google Play services client is successfully connected.
*/
@Override
public void onConnected(Bundle connectionHint) {
getDeviceLocation();
// Build the map.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
/**
* Handles failure to connect to the Google Play services client.
*/
@Override
public void onConnectionFailed(@NonNull ConnectionResult result) {
// Refer to the reference doc for ConnectionResult to see what error codes might
// be returned in onConnectionFailed.
Log.d(TAG, "Play services connection failed: ConnectionResult.getErrorCode() = "
+ result.getErrorCode());
}
/**
* Handles suspension of the connection to the Google Play services client.
*/
@Override
public void onConnectionSuspended(int cause) {
Log.d(TAG, "Play services connection suspended");
}
/**
* Handles the callback when location changes.
*/
@Override
public void onLocationChanged(Location location) {
mCurrentLocation = location;
updateMarkers();
}
/**
* Manipulates the map when it's available.
* This callback is triggered when the map is ready to be used.
*/
@Override
public void onMapReady(GoogleMap map) {
mMap = map;
// Turn on the My Location layer and the related control on the map.
updateLocationUI();
// Add markers for nearby places.
updateMarkers();
// Use a custom info window adapter to handle multiple lines of text in the
// info window contents.
mMap.setInfoWindowAdapter(new GoogleMap.InfoWindowAdapter() {
@Override
// Return null here, so that getInfoContents() is called next.
public View getInfoWindow(Marker arg0) {
return null;
}
@Override
public View getInfoContents(Marker marker) {
// Inflate the layouts for the info window, title and snippet.
View infoWindow = getLayoutInflater().inflate(R.layout.custom_info_contents, null);
TextView title = ((TextView) infoWindow.findViewById(R.id.title));
title.setText(marker.getTitle());
TextView snippet = ((TextView) infoWindow.findViewById(R.id.snippet));
snippet.setText(marker.getSnippet());
return infoWindow;
}
});
/*
* Set the map's camera position to the current location of the device.
* If the previous state was saved, set the position to the saved state.
* If the current location is unknown, use a default position and zoom value.
*/
if (mCameraPosition != null) {
mMap.moveCamera(CameraUpdateFactory.newCameraPosition(mCameraPosition));
} else if (mCurrentLocation != null) {
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(
new LatLng(mCurrentLocation.getLatitude(),
mCurrentLocation.getLongitude()), DEFAULT_ZOOM));
} else {
Log.d(TAG, "Current location is null. Using defaults.");
mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(mDefaultLocation, DEFAULT_ZOOM));
mMap.getUiSettings().setMyLocationButtonEnabled(false);
}
}
/**
* Builds a GoogleApiClient.
* Uses the addApi() method to request the Google Places API and the Fused Location Provider.
*/
private synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.enableAutoManage(this /* FragmentActivity */,
this /* OnConnectionFailedListener */)
.addConnectionCallbacks(this)
.addApi(LocationServices.API)
.addApi(Places.GEO_DATA_API)
.addApi(Places.PLACE_DETECTION_API)
.build();
createLocationRequest();
}
/**
* Sets up the location request.
*/
private 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);
}
/**
* Gets the current location of the device and starts the location update notifications.
*/
private void getDeviceLocation() {
/*
* Request location permission, so that we can get the location of the
* device. The result of the permission request is handled by a callback,
* onRequestPermissionsResult.
*/
if (ContextCompat.checkSelfPermission(this.getApplicationContext(),
android.Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
mLocationPermissionGranted = true;
} else {
ActivityCompat.requestPermissions(this,
new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION);
}
/*
* Get the best and most recent location of the device, which may be null in rare
* cases when a location is not available.
* Also request regular updates about the device location.
*/
if (mLocationPermissionGranted) {
mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient,
mLocationRequest, this);
}
}
/**
* Handles the result of the request for location permissions.
*/
@Override
public void onRequestPermissionsResult(int requestCode,
@NonNull String permissions[],
@NonNull int[] grantResults) {
mLocationPermissionGranted = false;
switch (requestCode) {
case PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
mLocationPermissionGranted = true;
}
}
}
updateLocationUI();
}
/**
* Adds markers for places nearby the device and turns the My Location feature on or off,
* provided location permission has been granted.
*/
private void updateMarkers() {
if (mMap == null) {
return;
}
if (mLocationPermissionGranted) {
// Get the businesses and other points of interest located
// nearest to the device's current location.
@SuppressWarnings("MissingPermission")
PendingResult<PlaceLikelihoodBuffer> result = Places.PlaceDetectionApi
.getCurrentPlace(mGoogleApiClient, null);
result.setResultCallback(new ResultCallback<PlaceLikelihoodBuffer>() {
@Override
public void onResult(@NonNull PlaceLikelihoodBuffer likelyPlaces) {
for (PlaceLikelihood placeLikelihood : likelyPlaces) {
// Add a marker for each place near the device's current location, with an
// info window showing place information.
String attributions = (String) placeLikelihood.getPlace().getAttributions();
String snippet = (String) placeLikelihood.getPlace().getAddress();
if (attributions != null) {
snippet = snippet + "\n" + attributions;
}
mMap.addMarker(new MarkerOptions()
.position(placeLikelihood.getPlace().getLatLng())
.title((String) placeLikelihood.getPlace().getName())
.snippet(snippet));
}
// Release the place likelihood buffer.
likelyPlaces.release();
}
});
} else {
mMap.addMarker(new MarkerOptions()
.position(mDefaultLocation)
.title(getString(R.string.default_info_title))
.snippet(getString(R.string.default_info_snippet)));
}
}
/**
* Updates the map's UI settings based on whether the user has granted location permission.
*/
@SuppressWarnings("MissingPermission")
private void updateLocationUI() {
if (mMap == null) {
return;
}
if (mLocationPermissionGranted) {
mMap.setMyLocationEnabled(true);
mMap.getUiSettings().setMyLocationButtonEnabled(true);
} else {
mMap.setMyLocationEnabled(false);
mMap.getUiSettings().setMyLocationButtonEnabled(false);
mCurrentLocation = null;
}
}
}
如何使用你只嘗試設置標記時，地圖爲null –
是什麼'onLocChange'？ –