Seeing What TalkBack Sees š
One of the things we should be doing as Android developers is to ensure that our apps are as accessible as possible. There are a bunch of talks and articles that discuss the motivations behind current MDC a11y support, the basic steps to support a11y, testing overviews, even creating your own a11y service!
Thereās a lot of resources that tell me what I should do, but what I found sorely lacking is information on helping me figure out what to do when something goes wrong (and knowing me, something is always bound to go wrong).
For example, this is the upper part of my appās homepage.
When the cart action menu item is focused, we expect TalkBack to announce how many items are currently in the cart. However I noticed that sometimes TalkBack just out of the blue says the number (and just the number) after announcing ā2 items in cartā. Weird!
If only I could dive into what TalkBack āseesā so I could figure out how to fix the problem and make our TalkBack announcements less confusing. I havenāt found any mention of how to do this in the official Android docs, and it is by sheer luck that I stumbled upon this āØamazing āØ article by Midori Bowen from 2018(!).
Wait, what! š»
It turns out that deep in the bowels of TalkBackās developer settings is an option to āEnable node tree debuggingā. Midori links to the Android documentation on enabling this setting but that page has since been deleted. šæ
The ānode treeā being referred to here is basically how TalkBack interprets your view hierarchy. Having visibility on this would surely give us a lot of insight into what is going on under the hood.
Follow the steps outlined in the OG post to enable node tree debugging. Some things have changed in Android and in TalkBack since Midoriās post, but in general the steps in there should give you an idea of how to enable logging. For instance, instead of looking for āUnassignedā, assignable gestures are now subtitled āTap to assignā. On some devices, TalkBack allows multi-finger gestures, so thereās a lot of options to use to trigger node tree log dumps. If a gesture already has an action, you can still overwrite it if you wish to do so.
What do we have here? š¤
We can now trigger a dump of the node tree on any screen by using the gesture we have set in TalkBack.
At this point I want to reiterate to please do not be like me and spend an hour looking for where the logs actually are (I forgot that I have Logcat filters on š¤¦āā). They are in Logcat, with the tag TreeDebug
.
Hereās the partial output of the node tree (timestamps remove for verbosity):
The first few lines (lines 2ā9) pertain to the status bar stuff, so letās just ignore that. Our applicationās contents start at line 10 (type=TYPE_APPLICATION
) with all the views on the screen in the following lines. Each ViewGroup
is tabbed which is really helpful in figuring out how each node maps to the view hierarchy. There's a lot of information here and some things have changed since Midori's post, so I thought it would be good to review what we can see in the logs. Let's take line 18 for example:
(1100966)652.Switch:(668, 225 - 800, 357):CONTENT{See only Specials}:STATE{OFF}:not checked(action:FOCUS/A11Y_FOCUS/CLICK):focusable:clickable
The screen is actually a RecyclerView
, so let's also take a look at what information we receive:
At the end of:
I was able to glean all this information from the LogTree file in TalkBackās repo.
Note that aside from logging the node tree, TalkBack also logs the traversal order which may be useful when trying to figure out the order in which elements on the screen gets focus.
Fixing our issueā¦ maybe š
Going back to our original issue, the node tree gives us a clue (the cart menu item is in most screens of my app):
(1094239)652.ViewGroup:(948, 77 - 1080, 209):CONTENT{Cart: 2 items in Cart}(action:FOCUS/A11Y_FOCUS/CLICK):focusable:clickable
(1095200)652.TextView:(1008, 107 - 1023, 140):TEXT{2}(action:A11Y_FOCUS):supportsTextLocation
AHA! It looks like both the ViewGroup
as a whole and the TextView
itself can have focus (it looks like the TextView
itself does not have a value for CONTENT
, which is what TalkBack announces though), which may explain why I sometimes hear just the number?
I guess I still donāt have a definitive answer, but setting android:importantForAccessibility="no"
on the TextView
should not present a problem since enough context is already given to the user when the ViewGroup
gets focus.
I hope that as more and more people become a11y allies that we also get more attention on a11y tooling, and more technical articles focused on supporting a11y beyond the basics. For instance, did you know that we can change what Talkback says to provide more context on actionable content? For example, when selecting this ViewGroup
:
Double-tapping will bring the user to the edit store or delivery address screen
TalkBack will announce āDouble-tap to changeā instead of the default āDouble-tap to activateā. The former gives the user more context about what is expected to happen when they interact with the element. Come to think of it, thatās a good idea for our next a11y post! See you then! š
Originally published at https://zarah.dev on September 13, 2021.