Why the top couple of buttons aren't showing in my layout?

Question

I have a LinearLayout, containg a ScrollView of ViewFlipper layouts. I've only included the problematic layout within my ViewFlipper. For some reason the top couple of buttons aren't showing, from gps1 upwards. Does anyone know why this is?

<LinearLayout 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:padding="30dip">
    <ScrollView
        android:id="@+id/ScrollView01"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:fillViewport="false">
        <ViewFlipper 
            android:id="@+id/viewFlipper"
            android:layout_width="fill_parent" 
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <!--adding views to ViewFlipper-->
            <LinearLayout
                android:orientation="vertical"
                android:layout_height="wrap_content"
                android:layout_width="fill_parent"
                android:layout_gravity="center" >

                <Button 
                    android:id="@+id/accelerometer1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="getAccelerometer"
                    android:text="Get Accelerometer">
                </Button>

                <Button 
                    android:id="@+id/gps1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="getLocation"
                    android:text="Get GPS">
                </Button>

                <Button 
                    android:id="@+id/picture1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="takePicture"
                    android:text="Take picture">
                </Button>

                <Button 
                    android:id="@+id/video1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="takeVideo"
                    android:text="Take video">
                </Button>

                <Button 
                    android:id="@+id/picture2"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="takePicture"
                    android:text="Take picture">
                </Button>

                <Button 
                    android:id="@+id/audio1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="takeAudio"
                    android:text="Take audio">
                </Button>

                <TextView
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:text="Page 1" />

                <TextView
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:text="Question 1?"/>

                <EditText android:id="@+id/textbox1" 
                    android:layout_width="fill_parent" 
                    android:layout_height="wrap_content" 
                    android:background="@android:drawable/editbox_background"
                    android:text=""/>

                <Button 
                    android:id="@+id/gps2"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" 
                    android:onClick="getLocation"
                    android:text="Get GPS">
                </Button>

                <TextView
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:text="Question 2?" />

                <EditText android:id="@+id/textbox2" 
                    android:layout_width="fill_parent" 
                    android:layout_height="wrap_content" 
                    android:background="@android:drawable/editbox_background"
                    android:text=""/>

                <TextView
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:text="Question 3?" />

                <EditText android:id="@+id/textbox3" 
                    android:layout_width="fill_parent" 
                    android:layout_height="wrap_content" 
                    android:background="@android:drawable/editbox_background"
                    android:text=""/>
            </LinearLayout>
            </ViewFlipper>
            </ScrollView>
            </LinearLayout>

Answer 1

I ended up figuring this out myself. I took out the layout-gravity:center attribute from my ViewFlipper:

<ViewFlipper 
        android:id="@+id/viewFlipper"
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
        android:orientation="vertical" android:layout_marginTop="20dp">