The Android Up button, on the left side of an action bar, enables users to navigate to a parent screen.
http://developer.android.com/training/basics/actionbar/adding-buttons.html
"Android 4.1 (API level 16) or higher, or when using ActionBarActivity from the Support Library, performing Up navigation requires that you declare the parent activity in the manifest file and enable the Up button for the action bar."
Do the following:
1) Declare the parent activity in the manifest file.
<activity
android:name="com.abc.myapp.ChildActivity"
android:label="@string/title_activity_display_message"
android:parentActivityName="com.abc.myapp.MainActivity"
/>
2) Enable the up button.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_displaymessage);
// minSdkVersion 11 or higher:
getActionBar().setDisplayHomeAsUpEnabled(true);
}