Question

我在模拟器和Studio中使用Android Studio 2.2.3，API 23（Android 6.0 / M）。我理解，从API 23开始，您必须对调用危险权限的方法使用运行时权限（例如，在这种情况下为ACCESS_FINE_LOCATION）。在下面的代码中，我的getLastKnownLocation（）方法返回null（但Provider和LocationManager不为null）。不知道我做错了什么，但我觉得它与我如何编写运行时权限有关。任何见解将不胜感激。还应注意，在我的“模拟器位置”设置中，该应用程序未显示在“最近的位置请求”下。

public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener {

private GoogleMap mMap;
LocationManager locationManager;
String provider;
Location location;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
    mapFragment.getMapAsync(this);

    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    provider = locationManager.getBestProvider(new Criteria(), false);

    Log.i("Location Manager", locationManager.toString());     //not returning null
    Log.i("Provider", provider);                               //not returning null

    //Runtime permission request
    if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.ACCESS_FINE_LOCATION)) {
            Toast.makeText(getApplicationContext(), "<Explanation of permission request goes here>", Toast.LENGTH_SHORT).show();
        } else {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 1);
        }
    }

    else {
        location = locationManager.getLastKnownLocation(provider);
        if (location != null) {
            Log.i("Location info:", "not null");
        } else {
            Log.i("Location info:", "null");                   //always returns null, which means the if(ActivityCompat... statement returns false, ie. permission is granted
        }
    }
}


/**
 * Manipulates the map once available.
 * This callback is triggered when the map is ready to be used.
 * This is where we can add markers or lines, add listeners or move the camera. In this case,
 * we just add a marker near Sydney, Australia.
 * If Google Play services is not installed on the device, the user will be prompted to install
 * it inside the SupportMapFragment. This method will only be triggered once the user has
 * installed Google Play services and returned to the app.
 */
@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    // Add a marker in Sydney and move the camera
    LatLng sydney = new LatLng(-34, 151);
    mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}

@Override
public void onLocationChanged(Location location) {

}


@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {

    if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        Log.i("Permission", "Permission granted");
    } else {
        Log.i("Permission", "Permission denied");
    }

}
}

在清单中我有：

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />

另外，我试图在API 21中编写类似的代码，因为它应该不使用运行时权限，但它仍然提示我包含运行时权限。任何人都知道如何在API 21中绕过这个？我是否必须使用早期版本的android studio？

Answer 1

getLastKnowLocation()返回上一个已知位置。它可用于快速修复，直到提供更准确的位置。要注册位置更新，您必须致电requestLocationUpdates()

Read this API Guide

getLastKnownLocation（）返回null并且应用程序未在模拟器上的“最近位置请求”下显示

1 个答案: