How to change the default icon on the SearchView, to be use in the action bar on Android?

I’ve found another way to change the search icon which goes in the same line as Diego Pino’s answer but straight in onPrepareOptionsMenu.

In your menu.xml (same as before)

<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item android:id="@+id/action_search"
      android:icon="@drawable/ic_action_fav"
      android:title="@string/action_websearch"
      android:showAsAction="always|never"
      android:actionViewClass="android.widget.SearchView" />
</menu>

In your activity:

@Override
public boolean onPrepareOptionsMenu(Menu menu) {
    MenuItem searchViewMenuItem = menu.findItem(R.id.action_search);    
    mSearchView = (SearchView) searchViewMenuItem.getActionView();
    int searchImgId = getResources().getIdentifier("android:id/search_button", null, null);
    ImageView v = (ImageView) mSearchView.findViewById(searchImgId);
    v.setImageResource(R.drawable.your_new_icon); 
    mSearchView.setOnQueryTextListener(this);
    return super.onPrepareOptionsMenu(menu);
}

I followed the example for changing the edittext in this example.

You should be able to do this for all icons/backgrounds in your SearchView, to find the right ID you can check here.

Hope this helps someone else as well!

UPDATE November 2017:

Since this answer android has been updated with the possibility of changing the search icon through the XML.

If you target anything below android v21 you can use:

<android.support.v7.widget.SearchView
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    app:searchIcon="@drawable/ic_search_white_24dp"
    app:closeIcon="@drawable/ic_clear_white_24dp" />

Or v21 and later:

<SearchView
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:searchIcon="@drawable/ic_search_white_24dp"
    android:closeIcon="@drawable/ic_clear_white_24dp" />

And there are even more options:

closeIcon
commitIcon
goIcon
searchHintIcon
searchIcon
voiceIcon