<menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/toolbar_search"
        android:icon="@mipmap/ic_search"
        android:title="搜索"
        android:orderInCategory="0"
        app:actionViewClass="android.support.v7.widget.SearchView"
        app:showAsAction="ifRoom|collapseActionView" />

    <item
        android:id="@+id/toolbar_collection"
        android:icon="@mipmap/ic_launcher"
        android:orderInCategory="1"
        android:title="收藏"
        app:showAsAction="never" />
    <item
        android:id="@+id/toolbar_share"
        android:orderInCategory="2"
        android:title="分享"
        app:showAsAction="never" />
    <item
        android:id="@+id/toolbar_fontsize"
        android:orderInCategory="3"
        android:title="字号"
        app:showAsAction="never" />
</menu>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v7.widget.Toolbar
        android:id="@+id/main_toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="@color/colorPrimary"/>
</RelativeLayout>

public class Singleton {
	private static Singleton instance;
    private Singleton (){}

	public static Singleton getInstance() {
	if (instance == null) {
		instance = new Singleton();
	}
		return instance;
	}
}