android - 如何在android中使用googlemaps v2知道何时到达具有一定半径的特定纬度

Question

我正在我的应用程序中实现类似导航的功能。在这里，我必须知道用户是否达到了特定的纬度/经度（比如在 XX 米之前）。我并不完全依赖 Location API 中可用的 distanceTo 方法。我必须知道移动的方向。

那么，我该如何实现呢？请帮我。

注意：我使用的是谷歌地图 v2 android。

Answer 1

使用接近警报：

我创建了一个小服务，指定警报的半径。

public class ProximityService extends Service {
String proximitysd = "com.apps.ProximityService";
int n = 0;
private BroadcastReceiver mybroadcast;
private LocationManager locationManager;
MyLocationListener locationListenerp;
private static final String PREFERENCE_NAME = "MyPreferenceFileName";
double lat;
double lng;
private static final String POINT_LATITUDE_KEY = "POINT_LATITUDE_KEY";
private static final String POINT_LONGITUDE_KEY = "POINT_LONGITUDE_KEY";

public ProximityService() {

}

@Override
public IBinder onBind(Intent intent) {
    // TODO Auto-generated method stub
    return null;
}

@Override
public void onCreate() {
    mybroadcast = new ProximityIntentReceiver();
    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    SharedPreferences prefs = this.getSharedPreferences(PREFERENCE_NAME,
            Context.MODE_PRIVATE);
    lat = prefs.getFloat(POINT_LATITUDE_KEY, 0);
    lng = prefs.getFloat(POINT_LONGITUDE_KEY, 0);

    float radius = 50f;
    long expiration = -1;
    // lat = cursor.getInt(MyDBAdapter.LATITUDE_COLUMN)/1E6;
    // lng = cursor.getInt(MyDBAdapter.LONGITUDE_COLUMN)/1E6;
    // lat = 12.923574064148527;
    // lng = 77.54726361483335;
    String what = "What";
    String how = "How";

    String proximitys = "ProximityService";

    IntentFilter filter = new IntentFilter(proximitys);
    registerReceiver(mybroadcast, filter);

    Intent intent = new Intent(proximitys);
    intent.putExtra("alert", what);
    intent.putExtra("type", how);

    PendingIntent proximityIntent = PendingIntent.getBroadcast(this, n,
            intent, PendingIntent.FLAG_CANCEL_CURRENT);
    locationManager.addProximityAlert(lat, lng, radius, expiration,
            proximityIntent);
    // sendBroadcast(new Intent(intent));

}

@Override
public void onDestroy() {
    Toast.makeText(this, "Proximity Service Stopped", Toast.LENGTH_LONG)
            .show();
    try {
        unregisterReceiver(mybroadcast);
    } catch (IllegalArgumentException e) {
        Log.d("reciever", e.toString());
    }

}

@Override
public void onStart(Intent intent, int startid) {

    // lat = id.getInt("lat");

    /*
     * Toast.makeText(this, "Proximity Service Started", Toast.LENGTH_LONG)
     * .show();
     */
    // IntentFilter filter = new IntentFilter(proximitys);
    // registerReceiver(mybroadcast,filter);

}

public class ProximityIntentReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context arg0, Intent intent) {
        // String key = LocationManager.KEY_PROXIMITY_ENTERING;
        final String key = LocationManager.KEY_PROXIMITY_ENTERING;
        final Boolean entering = intent.getBooleanExtra(key, false);
        // Boolean entering = arg1.getBooleanExtra(key, false);
        String here = intent.getExtras().getString("alert");
        String happy = intent.getExtras().getString("type");

        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        PendingIntent pendingIntent = PendingIntent.getActivity(arg0, 0,
                intent, 0);

        Notification notification = createNotification();

        if (entering) {
            Toast.makeText(getApplicationContext(), "entering",
                    Toast.LENGTH_SHORT).show();
            notification.setLatestEventInfo(arg0, "Entering Proximity!",
                    "", pendingIntent);
        } else {
            Toast.makeText(getApplicationContext(), "exiting",
                    Toast.LENGTH_SHORT).show();
            notification.setLatestEventInfo(arg0, "Existing Proximity!",
                    "", pendingIntent);
        }

        notificationManager.notify((int) System.currentTimeMillis(),
                notification);

    }

    private Notification createNotification() {
        Notification notification = new Notification();

        notification.icon = R.drawable.ic_launcher;
        notification.when = System.currentTimeMillis();

        notification.flags |= Notification.FLAG_AUTO_CANCEL;
        notification.flags |= Notification.FLAG_SHOW_LIGHTS;

        notification.defaults |= Notification.DEFAULT_VIBRATE;
        notification.defaults |= Notification.DEFAULT_LIGHTS;

        notification.ledARGB = Color.WHITE;
        notification.ledOnMS = 1500;
        notification.ledOffMS = 1500;

        return notification;
    }
    // make actions

}

public class MyLocationListener implements LocationListener {
    public void onLocationChanged(Location location) {
        Toast.makeText(getApplicationContext(), "I was here",
                Toast.LENGTH_LONG).show();
    }

    public void onProviderDisabled(String s) {
    }

    public void onProviderEnabled(String s) {
    }

    @Override
    public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
        // TODO Auto-generated method stub

    }
}

}