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/*
* Copyright (C) 2012 The Android Open Source Project
*
* 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.android.server.location;
import android.location.Location;
/**
* Represents a simple circular GeoFence.
*/
public class Geofence {
public final static int FLAG_ENTER = 0x01;
public final static int FLAG_EXIT = 0x02;
static final int STATE_UNKNOWN = 0;
static final int STATE_INSIDE = 1;
static final int STATE_OUTSIDE = 2;
final double mLatitude;
final double mLongitude;
final float mRadius;
final Location mLocation;
int mState; // current state
double mDistance; // current distance to center of fence
public Geofence(double latitude, double longitude, float radius, Location prevLocation) {
mState = STATE_UNKNOWN;
mLatitude = latitude;
mLongitude = longitude;
mRadius = radius;
mLocation = new Location("");
mLocation.setLatitude(latitude);
mLocation.setLongitude(longitude);
if (prevLocation != null) {
processLocation(prevLocation);
}
}
/**
* Process a new location.
* @return FLAG_ENTER or FLAG_EXIT if the fence was crossed, 0 otherwise
*/
public int processLocation(Location location) {
mDistance = mLocation.distanceTo(location);
int prevState = mState;
//TODO: inside/outside detection could be made more rigorous
boolean inside = mDistance <= Math.max(mRadius, location.getAccuracy());
if (inside) {
mState = STATE_INSIDE;
} else {
mState = STATE_OUTSIDE;
}
if (prevState != 0 && mState != prevState) {
if (mState == STATE_INSIDE) return FLAG_ENTER;
if (mState == STATE_OUTSIDE) return FLAG_EXIT;
}
return 0;
}
public double getDistance() {
return mDistance;
}
@Override
public String toString() {
String state;
switch (mState) {
case STATE_INSIDE:
state = "IN";
break;
case STATE_OUTSIDE:
state = "OUT";
break;
default:
state = "?";
}
return String.format("(%.4f, %.4f r=%.0f d=%.0f %s)", mLatitude, mLongitude, mRadius,
mDistance, state);
}
}
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