Some toolbar resources

here

to let the content width match_parent:

• you can use relative layout as the parent and it will do the work

or

• get the actionbar and set the custom view manually with layout params to match parent

supportActionBar?.displayOptions = ActionBar.DISPLAY_SHOW_CUSTOM
val params = ActionBar.LayoutParams(
    ActionBar.LayoutParams.MATCH_PARENT,
    ActionBar.LayoutParams.MATCH_PARENT
)
supportActionBar?.setCustomView(customToolbarContent2, params)