模式匹配

Question

Scala中的Programming中有以下示例：

<FrameLayout 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="com.example.nirvan.fragment_example.fragmentOne">

<!-- TODO: Update blank fragment layout -->

<ListView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/list"
    android:layout_gravity="left|top" />


</FrameLayout>

只打印苹果和橙色，因为无与某些（f）不匹配。

按照这个例子，我希望这次打印“无”：

import android.support.v4.app.Fragment;
import android.app.ListFragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

import android.view.View;


public class MainActivity extends AppCompatActivity{

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

    public void FragmentOneClick(View v)
    {
        ListFragment myFragment=new fragmentOne();
        FragmentManager fm= getFragmentManager();

        FragmentTransaction ft=fm.beginTransaction();
        ft.replace(R.id.fragment_switch, (android.app.Fragment) myFragment );
        ft.commit();
    }

    public void FragmentTwoClick(View v)
    {
        Fragment myFragment=new fragmentTwo();
        FragmentManager fm= getFragmentManager();

        FragmentTransaction ft=fm.beginTransaction();
        ft.replace(R.id.fragment_switch, myFragment);
        ft.commit();
    }
}

<?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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.nirvan.fragment_example.MainActivity">

    <Button
        android:onClick="FragmentOneClick"
    android:text="Fragment1"
    android:id="@+id/button1"
    android:layout_height="wrap_content"
    android:layout_width="150dp"
        android:layout_weight="2"
    >
    </Button>

<Button
    android:text="Fragment2"
    android:id="@+id/button2"
    android:onClick="FragmentTwoClick"
    android:layout_height="wrap_content"
    android:layout_width="150dp"
    android:layout_alignTop="@+id/button1"
    android:layout_alignRight="@+id/fragment_switch"
    android:layout_alignEnd="@+id/fragment_switch">
    android:layout_weight="2"
</Button>

<fragment
    android:id="@+id/fragment_switch"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginLeft="5dp"
    android:layout_marginRight="5dp"
    android:layout_marginBottom="5dp"
    android:layout_below="@+id/button1"
    android:name="com.example.nirvan.fragment_example.fragmentOne"
    tools:layout="@layout/fragment_fragment_one" />

</RelativeLayout>

但事实证明它打印出来了：

val fruits = List(Some("apple"), None, Some("orange"))
for(Some(f) <- fruits) println(f)

有谁可以解释我在这里缺少的东西？