Droidcon 2013 accessible android apps sharma_google

Designing Accessible
Android Applications
April 9, 2013

Google Confidential and Proprietary

Agenda

● What is accessibility?
● What features are available?
● How do you make your app accessible?
● Testing and Debugging


What framework provides

● User interactions and system events generate
AccessibilityEvents and send them to services
● AccessibilityServices like TalkBack respond to
these events and provide feedback to the user



Donut (1.6) through Honeycomb (3.x)
● Spoken feedback through TextToSpeech APIs
● Modify your device's display and sound options
○ Large text
○ Change speed at which text is spoken
○ Disable screen rotation

Ice Cream Sandwich (4.0)
● Touch exploration for devices without D-Pad
● Services can inspect view hierarchy



JellyBean (4.1)
● Supports Accessibility focus
○ Services can place this focus
on any view
○ Indicated on-screen via
yellow rectangle

● Supports Braille I/O devices
via BrailleBack service



JellyBean (4.1)
● Many actions available
○ Move input focus
○ Click on views
○ Scroll within views
○ Navigate text by words, etc.
○ Perform global actions


Features in Jelly Bean

Gestures
● Services can respond to user-
drawn gestures
○ Perform accessibility actions
○ Invoke global actions (Home,
Back, etc.)

● Deterministic access to
screen content



Magnification
● Available in Android 4.2
● Multiple zoom modes
○ Triple-tap to toggle
○ Triple-tap and hold for
momentary zoom



Gestures
● Quick shortcuts available in
Global Context Menu
○ Pause feedback
○ Repeat/spell last utterance
○ TalkBack Settings


(demo)



Android sensors

● SMS, Video chats, Videos with Captions
● Location aware, GPS, maps, places
● proximity
● eyes free - motion / accelerometer / velocity tracker / light sensor
● motion, environmental and position sensors

Read the Android Developer Guide for Sensors


Google Play
● Paid apps in many Countries
● DCB

Developer Console
● Countries and currencies
● Auto Translate feature
● Statistics

Global accessibility
● i18n and l10n

Read the Android Developer Guide for Localization



Design recommendations
● Navigation should be easy
● Use recommended touch target sizes
● Alternatives to time-out controls
● Label UI elements meaningfully
○ Minimize Chatter
○ Provide feedback

Read the Android Design Guide for Accessibility


Code changes for Accessibility

Labeling content
● Controls without text need android:contentDescription
● Android Lint tool warns when images are missing descriptions
● Purely decorative Views should set android:
contentDescription="@null"
● Use setContentDescription() to update a View's description
○ Don't override getContentDescription()
● EditTexts should use android:hint



Supporting D-Pad navigation
● Prior to Android 4.0, app needs to be accessible via D-Pad
○ Includes arrow keys on USB and Bluetooth keyboards
○ This is easy to test in the emulator!
● May need to manually specify that clickable items (e.g.
ImageViews) are focusable using android:focusable="true"
● Make important text focusable
● Control order using android:nextFocusDown



Supporting scaled text
● Android supports large fonts for low-vision use
● Text sizes should be in sp "scaled pixels" instead of dips
● Always test your app for text cropping, wrapping, etc.
○ You should be doing this for i18n anyway!

<TextView android:id="@+id/intro_text"
android:textSize="14sp"
.... />


Logical grouping and ordering

● View hierarchy order and on-screen positioning determine grouping
for accessibility focus and ordering of spoken feedback
● Group non-focusable items (e.g. TextViews) in a focusable
container to have them read as a single item
● Set content description on a container to override automatic
grouping and ordering of contained items


Logical grouping and ordering


FolderIcon android:id="@+id/folder"
android:focusable="true"
android:contentDescription="@string/folder_google"
...>
<ImageView android:id="@+id/preview_background"
android:contentDescription="@null"
... />
<BubbleTextView android:id="@+id/folder_icon_name"
android:text="@string/google"
... />
</LinearLayout>


Testing and Debugging for Accessibility

For all Android apps

○ Create checklist
○ Check with real simulation
○ Test on all supported Platforms
○ Test on screens and densities
Screens: small, normal, large, xlarge
Densities: (low (ldpi), medium (mdpi), high (hdpi),
extra high (xhdpi))


Testing and Debugging for
Accessibility

For all Android apps
● Enable Accessibility features
○ Turn on TalkBack logging in
Accessibility > TalkBack >
Settings > Developer
settings

● Android Lint tool


Summary

Must do:
● Use built-in Android components
○ Label controls
○ Make controls focusable
○ Ensure traversal order is correct
○ Specify text in sp
○ Logically group UI elements
● Fix custom components
○ Implement accessibility interfaces
○ Use Support library
○ TouchExplorationHelper is available on Google Code
● Test and Fix


Summary

Good to have:
● Augment audio-only prompts
○ Visual cues
○ Haptic feedback
● Evaluate sensors
● Add captions to videos
● Follow UI guidelines
● Reach globally

Read the Android Developer Guide for Accessibility


Thanks and Questions?

Send feedback to:
soniash@google.com


Droidcon 2013 accessible android apps sharma_google

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