When to request permission at runtime for Android Marshmallow 6.0?

In general, request needed permissions it as soon as you need them. This way you can inform the user why you need the permission and handle permission denies much easier.

Think of scenarios where the user revokes the permission while your app runs: If you request it at startup and never check it later this could lead to unexpected behaviour or exceptions.

In my opinion, there is no one correct answer to your question. I strongly suggest you to look at this official permissions patterns page.

Couple of things suggested by Google :

"Your permissions strategy depends on the clarity and importance of the permission type you are requesting. These patterns offer different ways of introducing permissions to the user."

"Critical permissions should be requested up-front. Secondary permissions may be requested in-context."

"Permissions that are less clear should provide education about what the permission involves, whether done up-front or in context."

This illustration might give you better understanding.

Maybe the most crucial thing here is that whether you ask the permission up-front or in the context, you should always keep in mind that these permissions can be revoked anytime by the user (e.g. your app is still running, in background).

You should make sure that your app doesn't crash just because you asked the permission on the very beginning of the app and assumed that user didn't change his/her preference about that permission.

Do like this

private static final int  REQUEST_ACCESS_FINE_LOCATION = 111;

In your onCreate

boolean hasPermissionLocation = (ContextCompat.checkSelfPermission(getApplicationContext(),
            Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED);
    if (!hasPermissionLocation) {
        ActivityCompat.requestPermissions(ThisActivity.this,
                new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                REQUEST_ACCESS_FINE_LOCATION);
    }

then check result

   @Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    switch (requestCode)
    {

        case REQUEST_ACCESS_FINE_LOCATION: {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
            {
                Toast.makeText(ThisActivity.this, "Permission granted.", Toast.LENGTH_SHORT).show();

                //reload my activity with permission granted
                finish();
                startActivity(getIntent());

            } else
            {
                Toast.makeText(ThisActivity.this, "The app was not allowed to get your location. Hence, it cannot function properly. Please consider granting it this permission", Toast.LENGTH_LONG).show();
            }
        }

    }

}

This is worked for me !!! In Your Splash Activity of your application do the following,

1) Declare an int variable for request code,

private static final int REQUEST_CODE_PERMISSION = 2;

2) Declare a string array with the number of permissions you need,

 String[] mPermission = {Manifest.permission.READ_CONTACTS, Manifest.permission.READ_SMS,
 Manifest.permission.ACCESS_FINE_LOCATION,
 Manifest.permission.WRITE_EXTERNAL_STORAGE};

3) Next Check the condition for runtime permission on your onCreate method,

try {
            if (ActivityCompat.checkSelfPermission(this, mPermission[0])
                    != MockPackageManager.PERMISSION_GRANTED ||
                    ActivityCompat.checkSelfPermission(this, mPermission[1])
                            != MockPackageManager.PERMISSION_GRANTED ||
                    ActivityCompat.checkSelfPermission(this, mPermission[2])
                            != MockPackageManager.PERMISSION_GRANTED ||
                    ActivityCompat.checkSelfPermission(this, mPermission[3])
                            != MockPackageManager.PERMISSION_GRANTED) {

                ActivityCompat.requestPermissions(this,
                        mPermission, REQUEST_CODE_PERMISSION);

              // If any permission aboe not allowed by user, this condition will execute every tim, else your else part will work
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

4) Now Declare onRequestPermissionsResult method to check the request code,

@Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        Log.e("Req Code", "" + requestCode);
        if (requestCode == REQUEST_CODE_PERMISSION) {
            if (grantResults.length == 4 &&
                    grantResults[0] == MockPackageManager.PERMISSION_GRANTED &&
                    grantResults[1] == MockPackageManager.PERMISSION_GRANTED &&
                    grantResults[2] == MockPackageManager.PERMISSION_GRANTED &&
                    grantResults[3] == MockPackageManager.PERMISSION_GRANTED) {

               // Success Stuff here

            }
        }

    }