Brtdku

I need to request camera and location permission in some activity that show the camera preview in surfaceview.

Where do I need to put the request permission function? onCreate, onResume, or onSurfaceCreated?

And where do I need to setup the camera?

See asking permission directly corresponds to the app crash if the service is requested and the permission is not available.
I would prefer to put the permission in onResume because whatever user action become i.e. like minimizing or a battery low dialog comes on top of screen, we need to check the permission changes again so that you activity changes might have occured through what ever reasons. Either camera is trying to open after network request or what the situation be.

Put the camera check permission in onResume.

So lets talk about how would you do it.
There are a number of perceptions. What I prefer to do is
I create a Helper class that would let me know the permission status with this code

class PermissionsHelper(activity: Activity) {

private val activity: Context



init { this.activity = activity }



fun isCameraPermissionAvailable()=ActivityCompat.checkSelfPermission(activity, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED

}

}

So in your activity's onResume method check if the permission is available else request the permission.

 override fun onResume() {

    super.onResume()

    if (!PermissionsHelper(this).isCameraPermissionAvailable()) {

        requestPermissions(arrayOf(Manifest.permission.CAMERA), CAMERA_REQUEST_CODE)

    }

}

Also please note two points

1) You should write permission for camera in manifeast so that app can request the permission

2) Check if the camera permission is available or not before opening the camera, if not you should again request for the permission

(same as in onResume stage)

First of all, define the permission in the manifest file.

In the java file,

You must request the permission again at runtime using checkSelfPermission. This is quite necessary as if you the user hasn't given the permission he won't be able to access the camera. You should write this code and all the functionality related to the camera when you want the camera to actually show up.

For example, if there is a button say Open Camera then first check for the permission if the user has granted or not and then open the camera.

You can place the permissions anywhere before using the service. Technically it doesn't matter. But asking for permission with a start-up screen providing the reason why the permission is needed or asking for it just before the service is used is user-friendly.

Perhaps the most relevant place to ask for permission as per Android documentation is

every time you perform an operation that requires that permission.

The reason behind such recommendation is Beginning with Android 6.0 (API level 23), users can revoke permissions from any app at any time. So even if the app used the camera yesterday, it can't assume it still has that permission today.

And hence app must "check" every time for the permission, to perform an operation that requires that permission.

You can setup Camera and other operations "after" the permission was granted to use the Camera by user. You can check the status if permission is granted by user by overriding onRequestPermissionsResult

@Override

public void onRequestPermissionsResult(int requestCode,

        String permissions, int grantResults) {

    switch (requestCode) {

        case MY_PERMISSIONS_REQUEST_CAMERA: {

            // If request is cancelled, the result arrays are empty.

            if (grantResults.length > 0

                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! Do the

                // camera-related task you need to do.

            } else {

                // permission denied, boo! Disable the

                // functionality that depends on this permission.

            }

            return;

        }



        // other 'case' lines to check for other

        // permissions this app might request.

    }

}