[Résolu] Utiliser la balise <include>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width=”match_parent”
    android:layout_height=”match_parent”
    android:background="@color/app_bg"
    android:gravity="center_horizontal">

    <include layout="@layout/titlebar"/>

    <TextView android:layout_width=”match_parent”
              android:layout_height="wrap_content"
              android:text="@string/hello"
              android:padding="10dp" />

    ...

</LinearLayout>