BackButton

UpButton vs BacKButton

http://developer.android.com/intl/zh-tw/design/patterns/navigation.html

how to create a activity with parent

<activity android:name=".Main2Activity">
    android:parentActivityName=".MainActivity"
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="pom2.poly.com.tryblacbutton.Main2Activity" />
</activity>

More detail:

http://developer.android.com/intl/zh-tw/training/basics/firstapp/starting-activity.html#CreateActivity