It should look like this:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@android:color/white"
android:weightSum="100" >
<LinearLayout
android:id="@+id/chart"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="80"
android:orientation="horizontal" />
<TextView
android:id="@+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="20"
android:gravity="center"
android:text="hello world"
android:textColor="@android:color/black" />
</LinearLayout>