Vertical Alignment gravity not responding

Question

Why won't this center the contents in the view?

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:layout_gravity="center_vertical"
    tools:context=".MainActivity">

    <EditText 
        android:id="@+id/messageTextField"
        android:layout_weight="1"
        android:inputType="number"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/messageTextFieldPlaceholder"
    />
    <Button
        android:id="@+id/sendButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/sendButtonTitle"
        android:onClick="sendMessage"
    />

</LinearLayout>

I saw a few SO threads about vertical alignment and I have also seen this, but I only have a horizontal LinearLayout, so setting the gravity will adjust the views from side to side.

Since the LinearLayout has the parent's dimensions, does it not fill the whole screen?

Shouldn't android:layout_gravity="center_vertical" align it's subviews in the center (vertically) of it's dimensions?

This is what makes sense to me across the coding that I've done, so why is android not making sense?

Do I need another LinearLayout that is vertical that holds everything else inside of it and have that with android:layout_gravity="center_vertical"?

Solution 1

layout_gravity:
Standard gravity constant that a child can supply to its parent.

gravity:
Specifies how to place the content of an object, both on the x- and y-axis, within the object itself.

So if you want your content to be vertically centered you need gravity not layout_gravity.

Solution 2

Instead of using android:layout_gravity="center_vertical", please use android:gravity="center_vertical", It will work...:)

Comments

[RileyE]

Okay. So, layout_gravity is for the contents as it communicates to it's layout and gravity would be for the layouts as it adjusts it's contents, right?

[Ahmad]

yes. layout_gravity -> child to parent, gravity -> parent to child.

[RileyE]

Thank you for the help. I had to go with Ahmad for the extra explanation, though.