content.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.jonathan.obd_bt.MainActivity"
    tools:showIn="@layout/activity_main">

    <RelativeLayout
        android:id="@+id/notchart"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:weightSum="3">

            <ScrollView
                android:id="@+id/top_scroll"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fillViewport="true"
                android:layout_weight="1"
                android:background="@android:drawable/dialog_holo_light_frame">

                <LinearLayout
                    android:id="@+id/value_texts"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:background="@drawable/centered_non_connected_bg"
                    android:paddingStart="4dp"
                    android:paddingEnd="4dp">

                    <TextView
                        android:id="@+id/placeholder"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:layout_gravity="center_vertical"
                        android:text="@string/not_connected_placeholder"
                        android:textAlignment="center"
                       
                        android:textColor="#aa000000"
                        android:textSize="20sp" />
                </LinearLayout>
            </ScrollView>
          ...