Question

I’m trying to copy some layout xml (which I can’t get to work), but I don’t understand how this works. Its drawing a divider with wrap content, but it has no content so how does it draw?

<TextView
    android:id="@+id/divider"
    android:layout_width="wrap_content"
    android:layout_height="1px"
    android:background="@color/medium_gray"
    android:layout_below="@id/spacer"
    android:layout_alignParentRight="true"
    android:layout_marginRight="@dimen/gutter_right"
    android:layout_toRightOf="@id/image" />

Answer 1

If I had to guess, they put content in it somewhere in the code. They make the background grey, but the height is only 1 pixel high, so if you fill the TextView with blank spaces it will make a grey line that are 1 pixel in height.

Anyway, the constant wrap_content means that the size of the view is dependent on the content is contains. In the case of a TextView, it will be as big as the characters it has to draw. If you changed it to fill_parent or match_parent, then the size will be bound based on the dimensions its parent determines.

If you did something like this:

<TextView
    android:id="@+id/divider"
    android:layout_width="match_parent"
    android:layout_height="1px"
    android:background="@color/medium_gray"
    android:layout_below="@id/spacer"
    android:layout_alignParentLeft="true"
    android:layout_alignParentRight="true"
    android:layout_marginRight="@dimen/gutter_right" />

Then it will draw a 1 pixel high grey line from the left side of the parent to the right side of the parent subtracting a margin from the right of size @dimen/gutter_right.

There’s no specific reason to use a TextView other than its a widget that doesn’t have drawing disabled, thus the background is drawn.