我是Android的新手，正在处理我的第一个应用程序。我正在开发一个应用程序，它需要连续的位置更新并在谷歌地图上显示。这意味着无论应用程序是在前台还是在后台。
同样我使用的是融合位置API的requestLocationUpdates。同一个viz有两个版本：
因此，根据我的理解，我必须使用两者，因为我需要持续更新。所以我在我的应用程序中使用两者，因为我需要不断更新。
但令人惊讶的是，我通过pendingIntent获得了requestLocationUpdates，并在前台提供了位置更新。所以我在这里很困惑，有时候将Location定位为NULL。
请告诉我requestLocationUpdates与pendingIntent的确切行为是什么。它对前景和背景都有效吗？如果是，那么为什么我在某个时候将位置变为NULL。
当我使用Locationreveiver时，另一个问题是，当应用程序处于前台时，我能够进行正确的位置更新，而我正在googlemap上绘制一条线。但我注意到我的线路与googlemap路线不同步。这是曲折的。所以我在这里感到困惑如果我得到持续更新，那么为什么m route与google route同步。
我正在附加我的位置类的complecode。请帮忙
public class LocationMapsActivity extends FragmentActivity implements
LocationListener,
OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
ComponentCallbacks2,
GoogleApiClient.OnConnectionFailedListener {
//*******************************member variables*********************************************
private static final String TAG = "LocationActivity";
private static final long INTERVAL = 1000 *02; // 1000*60*1 = 1 minute
private static final long FASTEST_INTERVAL = 1000 *01 ;// 10 sec
public static LatLng mPrev = null;
private double mCurrentDistance = 0;
private double mTotalDistance = 0;
private double mCurrentSpeed = 0;
public static String stateOfLifeCycle = "";
public static boolean wasInBackground = false;
LocationRequest mLocationRequest;
GoogleApiClient mGoogleApiClient;
Location mCurrentLocation;
Location mStartLocation;
GoogleMap googleMap;
//********************************************
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "onCreate ...............................");
wasInBackground = false;
stateOfLifeCycle = "Create";
//show error dialog if GoolglePlayServices not available
if (!isGooglePlayServicesAvailable()) {
finish();
}
createLocationRequest();
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
setContentView(R.layout.activity_map_location);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
//*******************ComponentCallbacks2*************************
@Override
public void onTrimMemory(int level) {
if (stateOfLifeCycle.equals("Stop")) {
wasInBackground = true;
}
super.onTrimMemory(level);
Toast.makeText(getApplicationContext(),
"Application OnTrimmemory ", Toast.LENGTH_SHORT)
.show();
}
//****************Activity****************************
@Override
public void onStart() {
Toast.makeText(getApplicationContext(),"OnStart ", Toast.LENGTH_SHORT).show();
Log.d(TAG, "onStart fired ..............");
stateOfLifeCycle = "Start";
if (wasInBackground) {
Toast.makeText(getApplicationContext(),"Application came to foreground",Toast.LENGTH_SHORT).show();
wasInBackground = false;
}
super.onStart();
if(!mGoogleApiClient.isConnected())
mGoogleApiClient.connect();
}
//********************Activity************************
@Override
public void onStop() {
stateOfLifeCycle = "Stop";
Log.d(TAG, "onStop fired ..............");
stopLocationUpdates();
// mGoogleApiClient.disconnect();
super.onStop();
Toast.makeText(getApplicationContext(), "OnStop ", Toast.LENGTH_SHORT).show();
Log.d(TAG, "isConnected ...............: " + mGoogleApiClient.isConnected());
}
//**************Activity******************************
@Override
protected void onPause() {
stateOfLifeCycle = "Pause";
super.onPause();
Toast.makeText(getApplicationContext(), "OnPause ", Toast.LENGTH_SHORT) .show();
}
//*******************Activity*************************
@Override
public void onResume() {
Toast.makeText(getApplicationContext(),"OnResume ", Toast.LENGTH_SHORT).show();
stateOfLifeCycle = "Resume";
super.onResume();
if (mGoogleApiClient.isConnected()) {
startLocationUpdates();
Log.d(TAG, "Location update resumed .....................");
}
}
//*****************Activity***************************
@Override
public void onDestroy()
{
wasInBackground = false;
stateOfLifeCycle = "Destroy";
super.onDestroy();
Toast.makeText(getApplicationContext(), "Application OnDestroy ", Toast.LENGTH_SHORT).show();
}
//******************OnMapReadyCallback**************************
@Override
public void onMapReady(GoogleMap map) {
googleMap = map;
googleMap.setMyLocationEnabled(true);
googleMap.getUiSettings().setZoomControlsEnabled(true);
//googleMap.setMapType(GoogleMap.MAP_TYPE_SATELLITE);
}
//*******************GoogleApiClient.ConnectionCallbacks*************************
@Override
public void onConnected(Bundle bundle) {
Log.d(TAG, "onConnected - isConnected ...............: " + mGoogleApiClient.isConnected());
startLocationUpdates();
}
//*******************GoogleApiClient.ConnectionCallbacks*************************
@Override
public void onConnectionSuspended(int i) {
}
//*****************GoogleApiClient.ConnectionCallbacks***************************
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
Log.d(TAG, "Connection failed: " + connectionResult.toString());
}
//*****************LocationListener***************************
// @Override
public void onLocationChanged(Location location) {
Log.d(TAG, "Firing onLocationChanged..............................................");
mCurrentLocation = location;
LatLng current = new LatLng(location.getLatitude(), location.getLongitude());
if(mPrev == null) //when the first update comes, we have no previous points,hence this
{
mPrev=current;
mStartLocation = location;
addMarker();
}
else {
CameraUpdate update = CameraUpdateFactory.newLatLngZoom(current, 17);
googleMap.animateCamera(update);
PolylineOptions pOptions = new PolylineOptions()
.width(7)
.color(Color.BLUE)
.visible(true);// .geodesic(true)
pOptions.add(mPrev);
pOptions.add(current);
googleMap.addPolyline(pOptions);
mPrev = current;
current = null;
}
}
//********************************************
protected void createLocationRequest() {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(INTERVAL);
mLocationRequest.setFastestInterval(FASTEST_INTERVAL);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
}
//********************************************
private boolean isGooglePlayServicesAvailable() {
int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
if (ConnectionResult.SUCCESS == status) {
Log.d(TAG, "isGooglePlayServicesAvailable ...............: SUCCESS" );
return true;
} else {
GooglePlayServicesUtil.getErrorDialog(status, this, 0).show();
return false;
}
}
//********************************************
protected void startLocationUpdates() {
//Get foreground location update
/* PendingResult<Status> pendingResult = LocationServices.FusedLocationApi.requestLocationUpdates(
mGoogleApiClient, mLocationRequest, this);*/
//Get background location update
String proximitys = "ACTION";
IntentFilter filter = new IntentFilter(proximitys);
getApplicationContext().registerReceiver(new LocationReceiver() , filter);
Intent intent = new Intent(proximitys);
// Intent intent = new Intent(this, LocationReceiver.class);
PendingIntent locationIntent = PendingIntent.getBroadcast(getApplicationContext(), 0, intent, PendingIntent.FLAG_CANCEL_CURRENT);
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, locationIntent);
}
//********************************************
public void HandleLocationChanged(Location location) {
Log.d(TAG, "Firing HandleLocationChanged..............................................");
// Toast.makeText(getApplicationContext(), "HandleLocationChanged", Toast.LENGTH_LONG).show();
if(location == null)
{
Toast.makeText(getApplicationContext(), "location is null", Toast.LENGTH_LONG).show();
return;
}
mCurrentLocation = location;
LatLng current = new LatLng(location.getLatitude(), location.getLongitude());
if(mPrev == null) //when the first update comes, we have no previous points,hence this
{
mPrev=current;
mStartLocation = location;
addMarker();
}
else {
CameraUpdate update = CameraUpdateFactory.newLatLngZoom(current, 17);
googleMap.animateCamera(update);
PolylineOptions pOptions = new PolylineOptions()
.width(7)
.color(Color.BLUE)
.visible(true);// .geodesic(true)
pOptions.add(mPrev);
pOptions.add(current);
googleMap.addPolyline(pOptions);
mPrev = current;
current = null;
}
}
//********************************************
public String getAddress( )
{
Geocoder geocoder = new Geocoder(this);
String addressLineTemp=null;
List<Address> addresses;
try {
addresses = geocoder.getFromLocation(mCurrentLocation.getLatitude(), mCurrentLocation.getLongitude(), 1);
if (addresses.size() > 0) {
addressLineTemp = addresses.get(0).getAddressLine(0);
}
} catch (IOException e) {
e.printStackTrace();
}
return addressLineTemp;
}
//********************************************
private void addMarker() {
MarkerOptions options = new MarkerOptions();
LatLng currentLatLng = new LatLng(mCurrentLocation.getLatitude(), mCurrentLocation.getLongitude());
options.position(currentLatLng);
Marker mapMarker = googleMap.addMarker(options);
mapMarker.setTitle(getAddress());
Log.d(TAG, "Marker added.............................");
googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(currentLatLng,
13));
Log.d(TAG, "Zoom done.............................");
}
//********************************************
protected void stopLocationUpdates() {
LocationServices.FusedLocationApi.removeLocationUpdates(
mGoogleApiClient, this);
Log.d(TAG, "Location update stopped .......................");
}
//********************************************
public class LocationReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent)
{
Log.d(TAG, "Firing LocationReceiver....onReceive..........................................");
Location location = (Location) intent.getExtras().get(LocationServices.FusedLocationApi.KEY_LOCATION_CHANGED);
HandleLocationChanged(location);
}
}