Question

Only ScrollView is visible?Y so?

<?xml version="1.0" encoding="utf-8"?><LinearLayout android:id="@+id/LinearLayout01"
android:layout_width="fill_parent" android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<ScrollView android:id="@+id/ScrollView01"
    android:layout_width="fill_parent" android:layout_height="110px">
    <LinearLayout android:id="@+id/LinearLayout02"
        android:layout_width="wrap_content" android:layout_height="30px"
        android:orientation="vertical">
        <Button android:text="1" android:id="@+id/Button01"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
        <Button android:text="2" android:id="@+id/Button02"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
        <Button android:text="3" android:id="@+id/Button03"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
    </LinearLayout>
</ScrollView>
<LinearLayout  android:id="@+id/LinearLayout02"
        android:layout_width="wrap_content" android:layout_height="30px"
        android:orientation="vertical">
        <Button android:text="1" android:id="@+id/Button01"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
        <Button android:text="2" android:id="@+id/Button02"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
        <Button android:text="3" android:id="@+id/Button03"
            android:layout_width="wrap_content" android:layout_height="wrap_content" />
    </LinearLayout>

Answer 1

Because you have set the orientation to the Parent LinearLayout as android:orientation="vertical".

As Default it has horizontal orientation.