Element LinearLayout doesn't have required attribute layout_height

Each TextView and Button as well as the LinearLayout tag complain ``` 'layout_height' attribute should be defined 'layout_width' attribute should be defined ``` This is my activity_main.xml: ``` <LinearLayout xmlns:android="http://schemas.android.com/apk/rest/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:layout_width="fill_parent" android:layout_height="fill_parent" android:text="@string/main_title" /> <Button android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/continue_label" /> <Button android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/new_game_label" /> <Button android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/about_label" /> <Button android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/exit_label" /> </LinearLayout> ``` I'm running Android Studio 1.1.0