Xamarin - Remove SearchBar Underline in Android

Question

I am trying to remove the black underline under the SearchBar Control on Android. I wrote a CustomRender that I thought would accomplish this, but no luck:

[assembly: ExportRenderer(typeof(NoUnderlineSearchBar), typeof(NoUnderlineSearchBarRenderer))]
namespace XamarinDemo.Droid.CustomRenderers
{
    public class NoUnderlineSearchBarRenderer : SearchBarRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
        {
            base.OnElementChanged(e);

            if (Control != null)
            {
                this.Control.SetBackgroundColor(Android.Graphics.Color.Argb(0, 0, 0, 0));
            }
        }
    }
}

This seems to work for Entry fields, but not SearchBars. Does anyone know how I can remove the SearchBar underline in a Custom Renderer? Thanks!

Answer 1

You're right about creating a custom renderer, but in your renderer, to remove the underline, we need to find the plate of SearchView in native android first. You can for example code like this:

protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
{
    base.OnElementChanged(e);

    if (Control != null)
    {
        var plateId = Resources.GetIdentifier("android:id/search_plate", null, null);
        var plate = Control.FindViewById(plateId);
        plate.SetBackgroundColor(Android.Graphics.Color.Transparent);
    }
}

Answer 2

This is to extend the answer above by @Grace.

In other examples I have came across following snippet:

protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
{
    base.OnElementChanged(e);

    if (Control != null)
    {
       LinearLayout linearLayout = this.Control.GetChildAt(0) as LinearLayout;
       linearLayout = linearLayout.GetChildAt(2) as LinearLayout;
       linearLayout = linearLayout.GetChildAt(1) as LinearLayout;

       linearLayout.Background = null; //removes underline
    }
}

However, on Android Lolipop and below linearLayout.Background = null; will result in

Attempt to invoke virtual method 'boolean android.graphics.drawable.Drawable.setState(int[])' on a null object reference xamarin search bar

Hence I would replace the code above on my answer with answer from Grace's as follows:

if (Control != null)
{
    var plateId = Resources.GetIdentifier("android:id/search_plate", null, null);
    var plate = Control.FindViewById(plateId);
    plate.SetBackgroundColor(Android.Graphics.Color.Transparent);
}