Uma forma de facilitar o uso do SearchView com a Toolbar

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.Toolbar
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/toolbar"
        android:layout_height="?attr/actionBarSize"
        android:layout_width="match_parent"
        android:minHeight="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

</RelativeLayout>

main_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/action_search"
        android:icon="@drawable/ic_magnify"
        android:title="Find"
        android:orderInCategory="50"
        app:showAsAction="always"
        app:actionViewClass="{{YOUR_PACKAGE}}.SearchView" />
</menu>

MainActivity.Java

import android.support.v4.view.MenuItemCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private SearchView searchView;
    private Toolbar toolbar;
    private static final String TAG = "tag";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);

        searchView = (SearchView) MenuItemCompat.getActionView(menu.findItem(R.id.action_search));
        searchView.setSearchableInfo(searchView.getManager().getSearchableInfo(getComponentName()));
        searchView.setIconified(true);

        searchView.setOnQueryTextListener(new android.support.v7.widget.SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                Log.d(TAG, "Submit: " + query);
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                Log.d(TAG, "Change: " + newText);
                return false;
            }
        });
        
        searchView.setOnCloseListener(new android.support.v7.widget.SearchView.OnCloseListener() {
            @Override
            public boolean onClose() {
                Toast.makeText(MainActivity.this, "Search View Closed", Toast.LENGTH_SHORT).show();
                return false;
            }
        });

        return true;
    }

    @Override
    public void onBackPressed() {
        if (searchView.isShown())
            searchView.hide();
        else
            super.onBackPressed();
    }
}

SearchView.java

import android.app.SearchManager;
import android.content.Context;
import android.util.AttributeSet;
import android.widget.ImageView;

/**
 * Created by Gustavo Fão Valvassori on 28/02/2016.
 * Propósito: Facilitar o uso do seachview
 */
public class SearchView extends android.support.v7.widget.SearchView {

    private SearchManager manager;

    private SearchAutoComplete mSearchSrcTextView;
    private ImageView mCloseButton;

    public SearchView(Context context) {
        super(context);
        __init__();
    }

    public SearchView(Context context, AttributeSet attrs) {
        super(context, attrs);
        __init__();
    }

    public SearchView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        __init__();
    }

    private void __init__() {
        mSearchSrcTextView = (SearchAutoComplete) findViewById(android.support.v7.appcompat.R.id.search_src_text);
        mCloseButton = (ImageView) findViewById(android.support.v7.appcompat.R.id.search_close_btn);

        manager = (SearchManager) getContext().getSystemService(Context.SEARCH_SERVICE);
    }

    public SearchManager getManager() {
        return manager;
    }

    public boolean isShown() {
        return mSearchSrcTextView.isShown();
    }

    public void hide() {
        mSearchSrcTextView.setText("");
        mCloseButton.performClick();
    }
}

styles.xml

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
    </style>

</resources>