android 定位

android 定位

参考：
android.location：https://developer.android.com/reference/android/location/package-summary.html
Location and Maps：https://developer.android.com/guide/topics/location/index.html#location
Location Strategies：https://developer.android.com/guide/topics/location/strategies.html
Location：https://developer.android.com/reference/android/location/Location.html

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下面介绍基于android框架APIs - android.location的定位。

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android定位框架 - android.location

有两种定位的方式：
1.基于GPS定位；
2.基于网络定位。

GPS定位的 好处 ：精确度高； 坏处 ：仅能在户外使用，获取定位信息速度慢，耗费电池。
网络定位的 好处 ：户内户外都能使用，定位速度快，电量耗费低； 坏处 ：精确度不太高。

我们可以综合使用两种定位方式，也可以单独使用其中一种

关键组件

LocationManager

android原生定位框架的核心组件是
LocationManager
系统服务，获取这个组件并不需要实例化，通常是通过函数
getSystemService(Context.LOCATION_SERVICE)
获得，该函数会返回一个LocationManager的实例，示例代码如下：

// Acquire a reference to the system Location Manager

LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);

LocationListener

通过回调（callback）来获取用户定位信息，首先我们需要通过新建一个
LocationListener
类，并实现其中的几个回调方法，示例代码如下：

// Define a listener that responds to location updatesLocationListener locationListener = new LocationListener() {    public void onLocationChanged(Location location) {      // Called when a new location is found by the network location provider.      // 这个函数中的location就是获取到的位置信息    }    public void onStatusChanged(String provider, int status, Bundle extras) {}    public void onProviderEnabled(String provider) {}    public void onProviderDisabled(String provider) {}  };    

同时我们需要调用函数 requestLocationUpdates 绑定

LocationManager和LocationListener，示例代码如下：      // Register the listener with the Location Manager to receive location updates    locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);

参数介绍：
第一个参数表示定位提供商的类型（the type of location provider），可以是
GPS_PROVIDER
或者
NETWORK_PROVIDER;
第二个参数表示更新定位信息的最短时间间隔；
第三个参数表示更新定位信息的最短改变距离；
第四个参数就是LocationListener实例。
注：如果第二个和第三个参数均为0表示尽可能快的更新定位信息

如果你想要获取同时使用两种定位方式，那么需要使用两次 requestLocationUpdate 函数，示例代码如下：

locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener); 

Location

这是一个数据类，保存了定位的信息，在

public void onLocationChanged(Location location)

中得到的location就是最新的定位信息，其中包括了维度（latitude），经度（longitude）等位置信息。

定位权限

定位功能的使用需要获取定位权限
如果使用 NETWORK_PROVIDER ，那么需要请求

android.permission.ACCESS_COARSE_LOCATION

如果使用 GPS_PROVIDER 或者同时使用上述两种定位方式，那么需要请求

android.permission.ACCESS_FINE_LOCATION

同时，如果你的app的运行环境是Android 5.0（API Level 21）或更高（If your app targets Android 5.0 (API level 21) or higher），那么你还需要显式请求

android.hardware.location.network
或者
android.hardware.location.gps

示例代码如下：

<manifest ... ><uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /><uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />...<!-- Needed only if your app targets Android 5.0 (API level 21) or higher. --><uses-feature android:name="android.hardware.location.gps" /><uses-feature android:name="android.hardware.location.network" />...</manifest>

同时当你的运行环境大于等于Android 6.0（API Level 23），你还需要在代码中显式进行权限检查，本次示例代码如下：

if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_DENIED) {    return ;}if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_DENIED) {    return ;}

示例

下面展示一个简单的应用示例：

新建一个工程LocationTest，使用默认Activity

MainActivity.java代码如下：

package com.zj.location;import android.Manifest;import android.content.Context;import android.content.pm.PackageManager;import android.location.Location;import android.location.LocationListener;import android.location.LocationManager;import android.support.v4.content.ContextCompat;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;public class MainActivity extends AppCompatActivity {    private static final String TAG = MainActivity.class.getSimpleName();    private LocationManager locationManager;    private LocationListener locationListener;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);        locationListener = new LocationListener() {            @Override            public void onLocationChanged(Location location) {                Log.d(TAG, "onLocationChanged: ");                Log.d(TAG, "onLocationChanged: latitude = "+location.getLatitude());                Log.d(TAG, "onLocationChanged: longitude = "+location.getLongitude());                Log.d(TAG, "onLocationChanged: provider = "+location.getProvider());            }            @Override            public void onStatusChanged(String provider, int status, Bundle extras) {            }            @Override            public void onProviderEnabled(String provider) {            }            @Override            public void onProviderDisabled(String provider) {            }        };        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_DENIED) {            return ;        }        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_DENIED) {            return ;        }        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);    }}

同时请求GPS定位信息以及Network定位信息，在 AndroidManifest.xml 中加入:

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /><uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /><uses-feature android:name="android.hardware.location.gps" /><uses-feature android:name="android.hardware.location.network" />

运行结果如下：

01-26 21:20:16.234 24056-24099/com.zj.location I/OpenGLRenderer: Initialized EGL, version 1.401-26 21:20:16.375 24056-24056/com.zj.location D/MainActivity: onLocationChanged: 01-26 21:20:16.376 24056-24056/com.zj.location D/MainActivity: onLocationChanged: latitude = 28.99117301-26 21:20:16.376 24056-24056/com.zj.location D/MainActivity: onLocationChanged: longitude = 120.25441101-26 21:20:16.376 24056-24056/com.zj.location D/MainActivity: onLocationChanged: provider = network01-26 21:20:46.471 24056-24056/com.zj.location D/MainActivity: onLocationChanged: 01-26 21:20:46.471 24056-24056/com.zj.location D/MainActivity: onLocationChanged: latitude = 28.99117301-26 21:20:46.472 24056-24056/com.zj.location D/MainActivity: onLocationChanged: longitude = 120.25441101-26 21:20:46.472 24056-24056/com.zj.location D/MainActivity: onLocationChanged: provider = network 

在logcat中显示出了手机的经纬度以及信息提供方

获取定位信息过程中遇到的问题

在android的官方文档中提到，获取到的定位信息可能包含错误或者存在精度问题

Challenges in Determining User Location

里面提到了3种原因：

• 多个定位源（Multitude of location sources）
• 手机的移动（User movement）
• 定位信息的精度问题（Varying accuracy）

创建最佳体验的定位模型

需要考虑下面几个问题

什么时候开始

长时间的监听定位更新会耗费大量的电量，但是，如果监听时间太短可能会导致定位精度问题。
开始监听定位更新是通过调用函数 requestLocationUpdates ，示例代码如下：

String locationProvider = LocationManager.NETWORK_PROVIDER;// Or, use GPS location data:// String locationProvider = LocationManager.GPS_PROVIDER;locationManager.requestLocationUpdates(locationProvider, 0, 0, locationListener);

获取最后已知的定位信息

在开始监听定位到获取到第一个定位信息可能会需要一段较长的时间，你可以利用函数 getLastKnownLocation 先获取一个缓存的定位信息，示例代码如下：

String locationProvider = LocationManager.NETWORK_PROVIDER;// Or use LocationManager.GPS_PROVIDERLocation lastKnownLocation = locationManager.getLastKnownLocation(locationProvider);  

注：这个定位信息有可能并不准确，也有可能和真正的位置一致

什么时候结束监听

因为长时间的监听定位会耗费大量的电量，所以当使用完定位功能后，可以手动移除定位监听，示例代码如下：

// Remove the listener you previously added
locationManager.removeUpdates(locationListener);

获取最佳定位

并不是最新得到的定位信息就是最好的，因为存在精度问题，可能最新获取的定位信息在精度和时间上并不是最好的，官方文档提到了几种方法来获取最佳的定位信息：

• 判断获取到的定位信息是否比当前定位信息更新（Check if the location retrieved is significantly newer than the previous estimate.）
• 判断获取到的定位信息的精度是否比当前定位信息更好（Check if the accuracy claimed by the location is better or worse than the previous estimate.）
• 判断获取到的定位信息的提供商是否是你更加信任的（Check which provider the new location is from and determine if you trust it more.）

官方的示例代码如下：

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  */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);}

示例2

利用上面提到的策略，修改代码

MainActivity.java代码如下：

package com.zj.location;import android.Manifest;import android.content.Context;import android.content.pm.PackageManager;import android.location.Location;import android.location.LocationListener;import android.location.LocationManager;import android.support.v4.content.ContextCompat;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;public class MainActivity extends AppCompatActivity {    private static final String TAG = MainActivity.class.getSimpleName();    private static final int TWO_MINUTES = 1000 * 60 * 2;    private final String NetworkProvider = LocationManager.NETWORK_PROVIDER;    private final String GpsProvider = LocationManager.GPS_PROVIDER;    private Location currentLocation;    private LocationManager locationManager;    private LocationListener locationListener;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);        locationListener = new LocationListener() {            @Override            public void onLocationChanged(Location location) {                Log.d(TAG, "onLocationChanged: ");                if (isBetterLocation(location, currentLocation)) {                    currentLocation = location;                    showLocation(currentLocation);                }            }            @Override            public void onStatusChanged(String provider, int status, Bundle extras) {            }            @Override            public void onProviderEnabled(String provider) {            }            @Override            public void onProviderDisabled(String provider) {            }        };        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_DENIED) {            return ;        }        if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_DENIED) {            return ;        }        Location lastKnownGpsLocation = locationManager.getLastKnownLocation(GpsProvider);        Location lastKnownNetworkLocation = locationManager.getLastKnownLocation(NetworkProvider);        showLocation(lastKnownGpsLocation);        showLocation(lastKnownNetworkLocation);        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);    }    private void showLocation(Location location) {        if (location == null) {            Log.e(TAG, "showLocation: location == null");            return ;        }        Log.d(TAG, "latitude = "+location.getLatitude());        Log.d(TAG, "longitude = "+location.getLongitude());        Log.d(TAG, "provider = "+location.getProvider());    }    /** 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     */    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);    }}

logcat 信息显示如下：

1-27 13:12:03.714 31281-31281/? V/BoostFramework: mReleaseFunc method = public int com.qualcomm.qti.Performance.perfLockRelease()01-27 13:12:03.714 31281-31281/? V/BoostFramework: mAcquireTouchFunc method = public int com.qualcomm.qti.Performance.perfLockAcquireTouch(android.view.MotionEvent,android.util.DisplayMetrics,int,int[])01-27 13:12:03.714 31281-31281/? V/BoostFramework: mIOPStart method = public int com.qualcomm.qti.Performance.perfIOPrefetchStart(int,java.lang.String)01-27 13:12:03.714 31281-31281/? V/BoostFramework: mIOPStop method = public int com.qualcomm.qti.Performance.perfIOPrefetchStop()01-27 13:12:03.716 31281-31281/? V/BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@71e6aaa01-27 13:12:03.753 31281-31281/com.zj.location W/System: ClassLoader referenced unknown path: /data/app/com.zj.location-1/lib/arm6401-27 13:12:03.768 31281-31281/com.zj.location W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable01-27 13:12:03.790 31281-31281/com.zj.location V/BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@be3f85001-27 13:12:03.790 31281-31281/com.zj.location V/BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@3994a4901-27 13:12:03.812 31281-31281/com.zj.location E/MainActivity: showLocation: location == null01-27 13:12:03.812 31281-31281/com.zj.location D/MainActivity: latitude = 28.99114101-27 13:12:03.812 31281-31281/com.zj.location D/MainActivity: longitude = 120.2544301-27 13:12:03.812 31281-31281/com.zj.location D/MainActivity: provider = network01-27 13:12:03.839 31281-31301/com.zj.location D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true01-27 13:12:03.850 31281-31281/com.zj.location D/ActivityThreadInjector: clearCachedDrawables.01-27 13:12:03.897 31281-31301/com.zj.location I/Adreno: QUALCOMM build                   : 0a3bdfc, Ifb508eebcd                                                         Build Date                       : 08/04/16                                                         OpenGL ES Shader Compiler Version: XE031.09.00.03                                                         Local Branch                     :                                                          Remote Branch                    :                                                          Remote Branch                    :                                                          Reconstruct Branch               : 01-27 13:12:03.902 31281-31301/com.zj.location I/OpenGLRenderer: Initialized EGL, version 1.401-27 13:12:04.056 31281-31281/com.zj.location D/MainActivity: onLocationChanged: 01-27 13:12:04.057 31281-31281/com.zj.location D/MainActivity: latitude = 28.99114101-27 13:12:04.057 31281-31281/com.zj.location D/MainActivity: longitude = 120.25443101-27 13:12:04.057 31281-31281/com.zj.location D/MainActivity: provider = network01-27 13:12:12.144 31281-31281/com.zj.location V/BoostFramework: BoostFramework() : mPerf = com.qualcomm.qti.Performance@288f8d601-27 13:12:34.255 31281-31281/com.zj.location D/MainActivity: onLocationChanged: 01-27 13:12:34.255 31281-31281/com.zj.location D/MainActivity: latitude = 28.99114101-27 13:12:34.256 31281-31281/com.zj.location D/MainActivity: longitude = 120.25443101-27 13:12:34.256 31281-31281/com.zj.location D/MainActivity: provider = network01-27 13:13:04.323 31281-31281/com.zj.location D/MainActivity: onLocationChanged: 01-27 13:13:04.324 31281-31281/com.zj.location D/MainActivity: latitude = 28.99114101-27 13:13:04.324 31281-31281/com.zj.location D/MainActivity: longitude = 120.25443101-27 13:13:04.324 31281-31281/com.zj.location D/MainActivity: provider = network01-27 13:13:34.401 31281-31281/com.zj.location D/MainActivity: onLocationChanged: 01-27 13:13:34.401 31281-31281/com.zj.location D/MainActivity: latitude = 28.99114101-27 13:13:34.401 31281-31281/com.zj.location D/MainActivity: longitude = 120.25443101-27 13:13:34.402 31281-31281/com.zj.location D/MainActivity: provider = network

提供模拟定位数据

当你使用模拟设备时，Android Studio可以提供模拟定位数据

Providing Mock Location Data