如何将操作添加到拆分ActionBar的顶部

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:elevation="4dp"
    android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
</android.support.v7.widget.Toolbar>

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

// 添加操作按钮
toolbar.inflateMenu(R.menu.menu_main);

<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_search"
        android:title="Search"
        app:showAsAction="always" />
    <item
        android:id="@+id/action_settings"
        android:icon="@drawable/ic_settings"
        android:title="Settings"
        app:showAsAction="always" />
</menu>

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.action_search) {
        // 执行搜索操作
        return true;
    } else if (id == R.id.action_settings) {
        // 打开设置界面
        return true;
    }

    return super.onOptionsItemSelected(item);
}