MainActivity to fragment and back to MainActivity on pressing back button

Question

I have a Mainactivity which contains a Layout which is parent of 4 sub layout. on clicking on sub layout i am going to a new fragment replacing main layout. But i cant go ba

Answer 1

Here is how it can be done in Xamarin:

Load fragment (I wrote helper method for that, but it's not necessary):

public void LoadFragment(Activity activity, Fragment fragment)
{
    var backStateName = fragment.GetType().Name;
    var fm = activity.FragmentManager;
    var ft = fm.BeginTransaction();

    ft.Replace(Resource.Id.mainContainer, fragment);
    ft.AddToBackStack(backStateName);

    ft.Commit();
}

Back button (in MainActivity):

public override void OnBackPressed()
{
    if (isNavDrawerOpen()) drawerLayout.CloseDrawers();
    else
    {
        var backStackEntryCount = FragmentManager.BackStackEntryCount;

        if (backStackEntryCount == 1) Finish();
        else if (backStackEntryCount > 1) FragmentManager.PopBackStack();
        else base.OnBackPressed();
    }
}

isNavDrawerOpen method:

bool isNavDrawerOpen()
{
    return drawerLayout != null && drawerLayout.IsDrawerOpen(Android.Support.V4.View.GravityCompat.Start);
}