AccessibilityWindowStateChangedEvent.md.html

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(#) Use of accessibility window state change events

!!! WARNING: Use of accessibility window state change events
   This is a warning.

Id
:   `AccessibilityWindowStateChangedEvent`
Summary
:   Use of accessibility window state change events
Severity
:   Warning
Category
:   Accessibility
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/AccessibilityWindowStateChangedDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/AccessibilityWindowStateChangedDetectorTest.kt)
Copyright Year
:   2024

Sending or populating `TYPE_WINDOW_STATE_CHANGED` events in your code is
strongly discouraged. Instead, prefer to use or extend system-provided
widgets that are as far down Android's class hierarchy as possible.
System-provided widgets that are far down the hierarchy already have
most of the accessibility capabilities your app needs. If you must
extend `View` or `Canvas` directly, then still prefer to: set UI
metadata by calling `Activity.setTitle`,
`ViewCompat.setAccessibilityPaneTitle`, or
`ViewCompat.setAccessibilityLiveRegion`; implement
`View.onInitializeAccessibilityNodeInfo`; and (for very specialized
custom controls) implement `View.getAccessibilityNodeProvider` to
provide a virtual view hierarchy. These approaches allow accessibility
services to inspect the view hierarchy, rather than relying on
incomplete information provided by events. Events like
`TYPE_WINDOW_STATE_CHANGED` will be sent automatically when updating
this metadata, and so trying to manually send this event will result in
duplicate events, or the event may be ignored entirely.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/com/my/app/MyView.kt:12:Warning: Manually populating or sending
TYPE_WINDOW_STATE_CHANGED events should be avoided. They may be ignored
on certain versions of Android. Prefer setting UI metadata using
View.onInitializeAccessibilityNodeInfo, Activity.setTitle,
ViewCompat.setAccessibilityPaneTitle, etc. to inform users of crucial
changes to the UI. [AccessibilityWindowStateChangedEvent]
    sendAccessibilityEvent(AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED)
    --------------------------------------------------------------------
src/com/my/app/MyView.kt:16:Warning: Manually populating or sending
TYPE_WINDOW_STATE_CHANGED events should be avoided. They may be ignored
on certain versions of Android. Prefer setting UI metadata using
View.onInitializeAccessibilityNodeInfo, Activity.setTitle,
ViewCompat.setAccessibilityPaneTitle, etc. to inform users of crucial
changes to the UI. [AccessibilityWindowStateChangedEvent]
    if (event.eventType == AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED) {
                                              -------------------------
src/com/my/app/MyView.kt:23:Warning: Manually populating or sending
TYPE_WINDOW_STATE_CHANGED events should be avoided. They may be ignored
on certain versions of Android. Prefer setting UI metadata using
View.onInitializeAccessibilityNodeInfo, Activity.setTitle,
ViewCompat.setAccessibilityPaneTitle, etc. to inform users of crucial
changes to the UI. [AccessibilityWindowStateChangedEvent]
    if (event.eventType == AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED) {
                                              -------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/com/my/app/MyView.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
package com.my.app

import android.content.Context
import android.view.View
import android.view.accessibility.AccessibilityEvent
import android.view.accessibility.AccessibilityNodeInfo
import android.widget.ScrollView

class MyView(context: Context) : View(context) {

  fun foo() {
    sendAccessibilityEvent(AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED)
  }

  override fun dispatchPopulateAccessibilityEvent(event: AccessibilityEvent): Boolean {
    if (event.eventType == AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED) {
      event.contentChangeTypes = AccessibilityEvent.CONTENT_CHANGE_TYPE_TEXT
    }
    return super.dispatchPopulateAccessibilityEvent(event)
  }

  override fun onPopulateAccessibilityEvent(event: AccessibilityEvent) {
    if (event.eventType == AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED) {
      event.contentChangeTypes = AccessibilityEvent.CONTENT_CHANGE_TYPE_TEXT
    }
    super.onPopulateAccessibilityEvent(event)
  }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/AccessibilityWindowStateChangedDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("AccessibilityWindowStateChangedEvent")
  fun method() {
     sendAccessibilityEvent(...)
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("AccessibilityWindowStateChangedEvent")
  void method() {
     sendAccessibilityEvent(...);
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection AccessibilityWindowStateChangedEvent
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="AccessibilityWindowStateChangedEvent" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'AccessibilityWindowStateChangedEvent'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore AccessibilityWindowStateChangedEvent ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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