通过 GPS 然后网络然后 Wifi 获取用户的位置

Question

我目前有一项服务，这种服务很有效。它检查是否启用了 GPS，如果启用，它将获取 GPS 位置，并且我的地图可以缩放到该位置。它有getLastKnownLocation。问题是，getLastKnownLocation 可能在数英里之外（就像我昨天尝试的那样）。

它首先运行 GPS 检查，因为它已启用它不会运行网络检查位置。

有没有办法让它在启用 GPS 的情况下，但除了 getLastKnownLcation() 之外无法修复，默认为基于网络的位置？之后我会检查，如果网络未启用或 lastKnownLocation 太远，我可以检查 Wifi。

这是我的服务代码：

public class GPSTracker extends Service implements LocationListener {

private final Context mContext;
boolean isGPSEnabled = false;
boolean isNetworkEnabled = false;
boolean canGetLocation = false;

Location location;
double latitude;
double longitude;

//Minimum distance for update
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; //10 meters

// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 40; //40 seconds

protected LocationManager locationManager;

public GPSTracker(Context context) {
    this.mContext = context;
    getLocation();
}

public Location getLocation() {
    Log.i("i", "Get location called");

    locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);

    //Getting GPS status
    isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

    //Getting network status
    isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
    this.canGetLocation = true;
    if (isGPSEnabled) {
        if (location == null) {
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
            Log.d("GPS Enabled", "GPS Enabled");
            if (locationManager != null) {
                location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                if (location != null) {
                    latitude = location.getLatitude();
                    longitude = location.getLongitude();
                    Log.i("GPS_LOCATION", "Location: "+location.toString());
                    if(location.toString().contains("0.000000")) {
                        Log.i("Called", "Called inside");
                        isNetworkEnabled = true;
                        isGPSEnabled = false;
                        getLocation();
                    }
                }
            }
        } 
    }
    else if (isNetworkEnabled) {
        Log.d("Network", "Network");
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this); 
        if (locationManager != null) {
            location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
            if (location != null) {
                latitude = location.getLatitude();
                longitude = location.getLongitude();
                Log.i("NETWORK_LOCATION", "Location: "+location.toString());
            }
        }
    }
    else if (!isGPSEnabled && !isNetworkEnabled) {
        // no network provider is enabled and GPS is off.
        Log.d("NOT ENABLED", "Use WIFI");
    }
    return location;
}

昨天发生的事情是，我离家几英里远，连接了 wifi 并启用了 GPS，但发生的情况是，虽然我的位置通过 Wifi 更新，但地图上出现了蓝点。它不会放大它。由于 GPS 已启用（但无法修复），它沿着这条路线走并得到了LastKnownLocation()，它回到了我家。即使蓝点是正确的，它仍会一直缩放到我上次所在的位置。

有没有办法让它检查 GPS 但不使用LastKnownLocation？相反，它默认为网络检查，然后网络检查将不使用lastknownLocation，它将默认为Wifi。如果需要，Wifi 可以有 LastKnownLocation。实际上，我只想在 Wifi 阶段获得lastKnownLocation 作为最后的手段。

希望有人可以帮助我。我不认为从代码中删除lastKnownLocation 这么简单。

感谢您提供的任何帮助。

Answer 1

有各种方法可以做到这一点。这里有一些提示：

1. 不要使用旧的 LastKnownLocation。先查年龄！
2. 位置通过getProvider() 提供提供程序，首先检查您是否拥有最高优先级，然后再处理次要。
3. 以最高精度使用 GPS。

您可能需要仔细查看Location Strategies，特别是isBetterLocation 函数。您可能想要这样的东西，尽管您需要对其进行调整以满足您的需要。

protected boolean isBetterLocation(Location location, Location currentBestLocation) {
    if (currentBestLocation == null) {
        // A new location is always better than no location
        return true;
    }

    // Check whether the new location fix is newer or older
    long timeDelta = location.getTime() - currentBestLocation.getTime();
    boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
    boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
    boolean isNewer = timeDelta > 0;

    // If it's been more than two minutes since the current location, use the new location
    // because the user has likely moved
    if (isSignificantlyNewer) {
        return true;
    // If the new location is more than two minutes older, it must be worse
    } else if (isSignificantlyOlder) {
        return false;
    }

    // Check whether the new location fix is more or less accurate
    int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
    boolean isLessAccurate = accuracyDelta > 0;
    boolean isMoreAccurate = accuracyDelta < 0;
    boolean isSignificantlyLessAccurate = accuracyDelta > 200;

    // Check if the old and new location are from the same provider
    boolean isFromSameProvider = isSameProvider(location.getProvider(),
            currentBestLocation.getProvider());

    // Determine location quality using a combination of timeliness and accuracy
    if (isMoreAccurate) {
        return true;
    } else if (isNewer && !isLessAccurate) {
        return true;
    } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
        return true;
    }
    return false;
}

/** Checks whether two providers are the same */
private boolean isSameProvider(String provider1, String provider2) {
    if (provider1 == null) {
      return provider2 == null;
    }
    return provider1.equals(provider2);
}