Question

I’ve been trying to start programming with the Android OS. Using the tutorials on the website I see that such views as LinearLayout, GridLayout use layout_width and layout_height xml attributes but the documentation never shows the inheritance of these attributes for these layouts. I have read where they’re required but don’t see how they can use something they never inherit.

Hopefully a simple question that has been bugging me.

Answer 1

Check http://developer.android.com/reference/android/view/ViewGroup.LayoutParams.html and http://developer.android.com/guide/topics/ui/declaring-layout.html

XML layout attributes named layout_something define layout parameters for the View that are appropriate for the ViewGroup in which it resides.

Every ViewGroup class implements a nested class that extends ViewGroup.LayoutParams. This subclass contains property types that define the size and position for each child view, as appropriate for the view group. As you can see in figure 1, the parent view group defines layout parameters for each child view (including the child view group).
Note that every LayoutParams subclass has its own syntax for setting values. Each child element must define LayoutParams that are appropriate for its parent, though it may also define different LayoutParams for its own children.

All view groups include a width and height (layout_width and layout_height), and each view is required to define them.