LocationHelper.java

/*
 * Copyright 2011 Matthew Precious
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mattprecious.locnotifier;

import java.io.IOException;
import java.util.List;

import android.content.Context;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;

import com.google.android.maps.GeoPoint;

/**
 * 
 * @author Google
 * 
 */
public class LocationHelper {
    private static final int TWO_MINUTES = 1000 * 60 * 2;

    /**
     * Determines whether one Location reading is better than the current
     * Location fix
     * 
     * @param location
     *            The new Location that you want to evaluate
     * @param currentBestLocation
     *            The current Location fix, to which you want to compare the new
     *            one
     */
    public static 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 static boolean isSameProvider(String provider1, String provider2) {
        if (provider1 == null) {
            return provider2 == null;
        }
        return provider1.equals(provider2);
    }

    public static GeoPoint getFirstPointFromSearch(Context context, String address) {
        List<Address> addressList = stringToAddresses(context, address);

        if (addressList == null) {
            return null;
        }

        return addressToPoint(addressList.get(0));
    }

    public static List<Address> stringToAddresses(Context context, String address) {
        try {
            Geocoder coder = new Geocoder(context);
            List<Address> result = coder.getFromLocationName(address, 10);

            return result;
        } catch (IOException e) {
            return null;
        }
    }

    public static GeoPoint addressToPoint(Address address) {
        if (address == null) {
            return null;
        }

        int latitude = (int) (address.getLatitude() * 1E6);
        int longitude = (int) (address.getLongitude() * 1E6);

        return new GeoPoint(latitude, longitude);
    }

    public static String addressToString(Address address) {
        StringBuilder builder = new StringBuilder();

        for (int i = 0; i < address.getMaxAddressLineIndex(); i++) {
            if (i > 0) {
                builder.append(", ");
            }

            builder.append(address.getAddressLine(i));
        }

        return builder.toString();
    }
}