Xamarin.Android 制作搜索框

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_weight="1"
        android:layout_height="match_parent"
        android:orientation="horizontal">
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="25dp"
            android:focusable="true"
            android:focusableInTouchMode="true"
            android:layout_marginTop="10dp"
            android:layout_marginLeft="10dp"
            android:layout_marginRight="10dp"
            android:background="@drawable/search_back">
            <ImageView
                android:layout_width="23dp"
                android:layout_marginTop="2dp"
                android:layout_height="23dp"
                android:layout_marginLeft="5dp"
                android:padding="2dp"
                android:layout_marginBottom="2dp"
                android:src="@drawable/icon_query" />
            <EditText
                android:id="@+id/et_search"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginLeft="30dp"
                android:padding="2dp" 
                android:background="@null"
                android:hint="搜索"
                android:layout_gravity="center_vertical"
                android:singleLine="true"
                android:textSize="17sp"
                android:textColor="#000000" />
        </RelativeLayout>
    </LinearLayout>
</LinearLayout>

using Android.App;
using Android.Widget;
using Android.OS;
using Android.Views;
using Android.Runtime;
using System;
using Android.Views.InputMethods;

namespace SearchDemo
{
    [Activity(Label = "SearchDemo", MainLauncher = true)]
    public class MainActivity : Activity, View.IOnKeyListener
    {
        EditText et_search; 

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

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            et_search = (EditText)FindViewById(Resource.Id.et_search);
            et_search.ImeOptions = Android.Views.InputMethods.ImeAction.Search;     //修改键盘按钮
            et_search.SetOnKeyListener(this);
        }

        public bool OnKey(View v, [GeneratedEnum] Keycode keyCode, KeyEvent e)
        {
            if (keyCode == Keycode.Enter || keyCode == Keycode.Search)
            {
                InputMethodManager imm = (InputMethodManager)this.GetSystemService(InputMethodService);
                if (imm != null)
                {
                    imm.HideSoftInputFromWindow(Window.DecorView.WindowToken, 0);       //隐藏键盘
                }
            }
            Toast.MakeText(this, et_search.Text, ToastLength.Short).Show();
            return false;
        }
    }
}

<shape xmlns:android="http://schemas.android.com/apk/res/android">
  <solid android:color="#F5F5F5" />
  <corners 
    android:topLeftRadius="4dp" 
    android:topRightRadius="4dp" 
    android:bottomRightRadius="4dp" 
    android:bottomLeftRadius="4dp" />
  <!--<stroke
     android:width="1dp"  
    />-->
</shape>