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!

score 19 · Accepted Answer · edited Jul 11 '20 at 10:22

19

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);
    }
}

edited Jul 11 '20 at 10:22

Neville Nazerane

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answered Mar 17 '17 at 02:46

Grace Feng

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Thanks, for that. How did you know the name of the first argument for GetIdentifier? Is there a good resource where this is documented? – MondQ Oct 15 '20 at 16:27
1

@MondQ, you can find the control id in layout resources: https://android.googlesource.com/platform/frameworks/base/+/fcdbcf9174f7a5404da4514b71041c3d37692d15/core/res/res/layout – Grace Feng Oct 19 '20 at 01:52

score 1 · Answer 2 · answered Apr 29 '18 at 16:38

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);
}

Xamarin - Remove SearchBar Underline in Android

2 Answers2

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