在“请求”中包装权限后仍然无法获取设备位置

Question

使用Android API版本23并添加了启用位置清单的权限：

<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.BODY_SENSORS"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.GPS_PROVIDER" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

在运行时请求权限的活动代码：

import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.Manifest;

public class MainActivity extends AppCompatActivity {

    LocationManager lm;
    Location location;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);


        ActivityCompat.requestPermissions(MainActivity.this,
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                1);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case 1: {

                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                } else {

                }
                return;
            }

        }
    }
}

但这一行：

                location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

导致错误：

我没有正确设置权限？

更新：

这是更新的代码：

import android.content.Context;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    LocationManager lm;
    Location location;

    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);

        int permissionCheck = ContextCompat.checkSelfPermission(this,
                android.Manifest.permission.ACCESS_FINE_LOCATION);
        location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

        Log.d(TAG, "location is "+location);
        if(location != null) {
            double longitude = location.getLongitude();
            double latitude = location.getLatitude();

            Log.d(TAG, "longitude : " + longitude);
            Log.d(TAG, "latitude : " + latitude);

        }
    }

}

我不再收到编译器错误，但location设置为mull。

在设备内启用了位置。

这是访问位置的正确方法吗？

更新2：

此处检查checkSelfPermission但location的权限为空：

import android.content.Context;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    LocationManager lm;
    Location location;

    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
        int permissionCheck = ContextCompat.checkSelfPermission(this,
                android.Manifest.permission.ACCESS_FINE_LOCATION);

        Log.d(TAG, "permissionCheck : " + permissionCheck);

        if(permissionCheck >= 0) {
            location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);

            Log.d(TAG, "location is " + location);
            if (location != null) {
                double longitude = location.getLongitude();
                double latitude = location.getLatitude();

                Log.d(TAG, "longitude : " + longitude);
                Log.d(TAG, "latitude : " + latitude);

            }
        }

    }

}