Android 检查 LocationManager 的权限

Question

当我点击我的 Activity 布局中的一个按钮时，我试图让 GPS 坐标显示。以下是单击按钮时调用的方法:

public void getLocation(View view) {
    TextView tv = (TextView) findViewById(R.id.gps_coord_view);
    LocationManager lm = (LocationManager) getSystemService(LOCATION_SERVICE);
    Location loc = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    tv.setText("Latitude: " + loc.getLatitude() + "\nLongitude: " + loc.getLongitude());
}

我收到一条错误提示

Call requires permission which may be rejected by user. Code should explicitly check to see if permission is available.

我已经在我的 AndroidManifest 中授予了这些权限。当我在调用 lm.getLastKnownLocation 之前添加以下内容时，该错误已得到解决，并且应用程序编译:

if (checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
        && checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
    return;
}

但是，当我按下调用 getLocation 的按钮时，应用程序会崩溃。到底是怎么回事？是否有更好/更简单的方法来获取设备的 GPS 坐标？

Answer 1

对于 Android API 级别 (23)，我们需要检查权限。 https://developer.android.com/training/permissions/requesting.html

我遇到了同样的问题，但以下方法对我有用，并且我能够成功检索位置数据:

(1) 确保您拥有 list 中列出的权限:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

(2) 确保您向用户请求权限:

if ( ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION ) != PackageManager.PERMISSION_GRANTED ) {

            ActivityCompat.requestPermissions( this, new String[] {  android.Manifest.permission.ACCESS_COARSE_LOCATION  },
                                                LocationService.MY_PERMISSION_ACCESS_COURSE_LOCATION );
        }

(3) 确保使用 ContextCompat，因为它与旧 API 级别兼容。

(4) 在你的位置服务，或者初始化你的 LocationManager 并获取最后一个已知位置的类中，我们需要检查权限:

if ( Build.VERSION.SDK_INT >= 23 &&
             ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED &&
             ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return  ;
        }

(5) 这种方法仅在我将 @TargetApi(23) 包含在我的 initLocationService 方法的顶部之后才对我有效。

(6) 我也将这个添加到我的 gradle 构建中:

compile 'com.android.support:support-v4:23.0.1'

这是我的 LocationService 供引用:

public class LocationService implements LocationListener  {

    //The minimum distance to change updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 0; // 10 meters

    //The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 0;//1000 * 60 * 1; // 1 minute

    private final static boolean forceNetwork = false;

    private static LocationService instance = null;

    private LocationManager locationManager;
    public Location location;
    public double longitude;
    public double latitude; 


    /**
     * Singleton implementation
     * @return
     */
    public static LocationService getLocationManager(Context context)     {
        if (instance == null) {
            instance = new LocationService(context);
        }
        return instance;
    }

    /**
     * Local constructor
     */
    private LocationService( Context context )     {

        initLocationService(context); 
        LogService.log("LocationService created");
    }



    /**
     * Sets up location service after permissions is granted
     */
    @TargetApi(23)
    private void initLocationService(Context context) {


        if ( Build.VERSION.SDK_INT >= 23 &&
             ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED &&
             ContextCompat.checkSelfPermission( context, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return  ;
        }

        try   {
            this.longitude = 0.0;
            this.latitude = 0.0;
            this.locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);

            // Get GPS and network status
            this.isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
            this.isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (forceNetwork) isGPSEnabled = false;

            if (!isNetworkEnabled && !isGPSEnabled)    {
                // cannot get location
                this.locationServiceAvailable = false;
            }
            //else
            {
                this.locationServiceAvailable = true;

                if (isNetworkEnabled) {
                    locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    if (locationManager != null)   {
                        location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                        updateCoordinates();
                    }
                }//end if

                if (isGPSEnabled)  {
                    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);

                    if (locationManager != null)  {
                        location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        updateCoordinates();
                    }
                }
            }
        } catch (Exception ex)  {
            LogService.log( "Error creating location service: " + ex.getMessage() );

        }
    }       


    @Override
    public void onLocationChanged(Location location)     {
        // do stuff here with location object 
    }
}

到目前为止，我仅使用 Android Lollipop 设备进行了测试。希望这对你有用。