(Xamarin.Forms) Picker 에 화살표 표시하기

Xamarin.Forms 콤보박스 컨트롤인 Picker 컨트롤에는 화살표시가 없습니다.

 

화살표시를 나타내기 위해서는 렌더러를 이용해야합니다.

우선 화살표 이미지를 먼저 구해야합니다. (전 아래 이미지로..)

  (downarrow)

사용할 이미지를 Android 프로젝트의 Resources/drawable 폴더에, iOS 프로젝트의 Resources 폴더에 추가합니다.

 

먼저 .Net Standard 프로젝트에

CustomPicker.cs 를 추가합니다.

using Xamarin.Forms;

namespace Test.Cntrol
{
    public class CustomPicker : Picker
    {
        public static readonly BindableProperty ImageProperty =
            BindableProperty.Create(nameof(Image), typeof(string), typeof(CustomPicker), string.Empty);

        public string Image
        {
            get { return (string)GetValue(ImageProperty); }
            set { SetValue(ImageProperty, value); }
        }

        public CustomPicker() : base()
        {
            Margin = 3;
        }
    }
}

 

Android 프로젝트에 CustomPickerRenderer.cs 를 추가합니다.

using Android.Content;
using Android.Graphics;
using Android.Graphics.Drawables;
using Android.Support.V4.Content;
using Test.Cntrol;
using Test.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(CustomPicker), typeof(CustomPickerRenderer))]
namespace Test.Droid
{
    public class CustomPickerRenderer : PickerRenderer
    {
        CustomPicker element;

        public CustomPickerRenderer(Context context) : base(context)
        {
        }

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

            element = (CustomPicker)this.Element;

            if (Control != null && this.Element != null && !string.IsNullOrEmpty(element.Image))
                Control.Background = AddPickerStyles(element.Image);
        }

        public LayerDrawable AddPickerStyles(string imagePath)
        {
            ShapeDrawable border = new ShapeDrawable();
            border.Paint.Color = Android.Graphics.Color.Gray;
            border.SetPadding(10, 10, 10, 10);
            border.Paint.SetStyle(Paint.Style.Stroke);

            Drawable[] layers = { border, GetDrawable(imagePath) };
            LayerDrawable layerDrawable = new LayerDrawable(layers);
            layerDrawable.SetLayerInset(0, 0, 0, 0, 0);

            return layerDrawable;
        }

        private BitmapDrawable GetDrawable(string imagePath)
        {
            int resID = Resources.GetIdentifier(imagePath, "drawable", this.Context.PackageName);
            var drawable = ContextCompat.GetDrawable(this.Context, resID);
            var bitmap = ((BitmapDrawable)drawable).Bitmap;

            var result = new BitmapDrawable(Resources, Bitmap.CreateScaledBitmap(bitmap, 70, 70, true));
            result.Gravity = Android.Views.GravityFlags.Right;

            return result;
        }
    }
}

 

iOS 프로젝트에도 CustomPickerRenderer.cs 를 추가합니다.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Foundation;
using Test.Cntrol;
using Test.iOS;
using UIKit;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(CustomPicker), typeof(CustomPickerRenderer))]
namespace Test.iOS
{
    public class CustomPickerRenderer : PickerRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
        {
            base.OnElementChanged(e);

            var element = (CustomPicker)this.Element;

            if (this.Control != null && this.Element != null && !string.IsNullOrEmpty(element.Image))
            {
                var downarrow = UIImage.FromBundle(element.Image);
                Control.RightViewMode = UITextFieldViewMode.Always;
                Control.RightView = new UIImageView(downarrow);
            }
        }
    }
}

 

이제 화면 상에서 아래 처럼 컨트롤을 정의한후 데이터를 바인딩하면

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:cntrol="clr-namespace:Test.Cntrol"
             x:Class="Test.MainPage">
    <StackLayout Spacing="5">
      
      <cntrol:CustomPicker x:Name="customPicker"
                           HeightRequest="40"
                           Margin="10"
                           Image="downarrow"
                           Title="Custom Picker"/>
    </StackLayout>
</ContentPage>

아래처럼 화살표시가 Picker 에 표시됩니다.