android:gravity="top" doesn't align child view to top, but "center" aligns to center?

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:gravity="top"   <!--this line-->
    android:orientation="horizontal" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0"
        android:textSize="56dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0"
        android:textSize="36dp" />
</LinearLayout>

Shouldn't that make the smaller "0" t-view align to the top of the inner LinearLayout? Since the other "0" is larger in height, it increases the overall height of the inner LinearLayout.

Alternatively, if you included this:

android:layout_gravity="top"

within the t-view of the smaller 0, it also does nothing. Why is this? Does the wrap_content of the LinearLayout wrap each individual view independent of others? If so, then why does setting gravity to "center" work? In the sense that the smaller zero is vertically centered to its parent.

I know you can just set the smaller 0's height to match parent and set its own gravity to top. I'm just trying to understand this. Thanks.

gravity attribute applies to widgets within the LinearLayout, while layout_gravity tells the parent of LinearLayout where to place the child (LinearLayout).

Also, in a vertical LinearLayout the gravity="top" attribute won't work.

In the layout you have now, both text views will be stacked one on top of the other, wrapped with a linear layout with no space in-between - so the "top" or "center" values won't do anything because there is no extra space to move the text views up or down.

If you want to understand this better, try giving your linear layout and both text views backgrounds of different colors, like this:

android:background="@color/mycolor"

Then you will see the bounds of each widget.