CheckableLayout
Accessibility
com.example.android.checkablelayout
16
PUBLISHED
Accessibility
Android
Java
Mobile
BEGINNER
screenshots/icon-web.png
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screenshots/checked.png
android.view.accessibility.AccessibilityNodeInfo
android.view.accessibility.AccessibilityEvent
Sample demonstrating how to make a simple custom view accessible.
Creates a simple `CheckableFrameLayout` that has the accessibility
profile of builtin that implements the `Checkable` interface (e.g.
`Checkbox`).
This sample implements a single custom view, a
`CheckableFrameLayout`, which implements the `Checkable` interface
and maintains a checked state.
This sample uses the custom view as a container for two overlayed
`]]>`s. The first `]]>` is
always displayed, while the second `]]>`'s
display status toggles with the checked state of it's parent (the
`CheckableLayout`). This second `]]>` uses
`android:duplicateParentState` (see `activity_main.xml`) and a
drawable that is tied to `android:state_checked` (see
`drawable/ic_checkable_item.xml`). This drawable is displayed only
when the parent is in a checked state.
This sample provides a basic introduction to Android accessibility
by showing how to make a custom view behave similar to a builtin
widget like a `Checkbox`.
Developers should focus on two methods that are overridden from the
parent class:
`onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info)` and
`onInitializeAccessibilityEvent(AccessibilityEvent event)`.
The `onInitializeAccessibilityNodeInfo()` method provides
accessibility services with information about the state of this
view. We override this method to tell an accessibility service that
this view is checkable, and we set the intitial checked state of the
view.
The `onInitializeAccessibilityEvent()` method is use by the
system to obtain additional information about the state of the view
as its state changes.
With this information, an accessibility service has what it needs to
allow a user to meaningfully discover the view and know its state.