Can you request permissions synchronously in Android Marshmallow (API 23)'s runtime permissions model?

Question

Say you have a method like this:

public boolean saveFile (Url url, String content) {

   // save the file, this can be done a lot of different ways, but
   // ba         


        

Answer 1

Here's how I solved the "synchronicity" issue without having to explicitly block (and busy-wait), or without requiring a separate "boot-loader" Activity. I refactored splash screen Activity as follows:

update: A more complete example can be found here.

---

note: Because the requestPermissions() API calls startActivityForResult()

public final void requestPermissions(@NonNull String[] permissions, int requestCode) {
    Intent intent = getPackageManager().buildRequestPermissionsIntent(permissions);
    startActivityForResult(REQUEST_PERMISSIONS_WHO_PREFIX, intent, requestCode, null);
}

the main view-creation logic was moved from OnCreate() to OnCreate2(), and OnCreate() now handles the permissions check. If RequestPermissions() needs to be called, then the associated OnRequestPermissionsResult() restarts this activity (forwarding a copy of the original bundle).

---

[Activity(Label = "MarshmellowActivated",
    MainLauncher = true,      
    Theme = "@style/Theme.Transparent",
    Icon = "@drawable/icon"        
    ////////////////////////////////////////////////////////////////
    // THIS PREVENTS OnRequestPermissionsResult() from being called
    //NoHistory = true
)]
public class MarshmellowActivated : Activity
{
    private const int ANDROID_PERMISSION_REQUEST_CODE__SDCARD = 112;
    private Bundle _savedInstanceState;

    public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Permission[] grantResults)
    {
        base.OnRequestPermissionsResult(requestCode, permissions, grantResults);

        switch (requestCode)
        {
            case ANDROID_PERMISSION_REQUEST_CODE__SDCARD:
                if (grantResults.Length > 0 && grantResults[0] == Permission.Granted)
                {       
                    Intent restartThisActivityIntent = new Intent(this, this.GetType());
                    if (_savedInstanceState != null)
                    {
                        // *ref1: Forward bundle from one intent to another
                        restartThisActivityIntent.PutExtras(_savedInstanceState);
                    }
                    StartActivity(restartThisActivityIntent);
                }
                else
                {                   
                    throw new Exception("SD Card Write Access: Denied.");
                }
                break;
        }
    }

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        ///////////////////////////////////////////////////////////////////////////////////////////////////////////
        // Android v6 requires explicit permission granting from user at runtime for extra sweet security goodness
        Permission extStoragePerm = ApplicationContext.CheckSelfPermission(Android.Manifest.Permission.WriteExternalStorage);

        //if(extStoragePerm == Permission.Denied)
        if (extStoragePerm != Permission.Granted)
        {
            _savedInstanceState = savedInstanceState;
            // **calls startActivityForResult()**
            RequestPermissions(new[] { Android.Manifest.Permission.WriteExternalStorage }, ANDROID_PERMISSION_REQUEST_CODE__SDCARD);
        }
        else
        {
            OnCreate2(savedInstanceState);
        }
    }

    private void OnCreate2(Bundle savedInstanceState)
    {
        //...
    }
}

ref1: Forward bundle from one intent to another

note: This can be refactored to handle more permissions generally. It currently handles the sdcard write permission only, which should convey the pertinent logic with sufficient clarity.