<?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, );       //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>