AccessibilityService不返回视图ID

Question

I'm writing an acessibility service in Android which relies on getting the view id of the currently selected view, however on some devices (Nexus 6P 6.0.1, Samsung Galaxy S6 edge+ 5 + 6.0.1) I get no view id through and on others (HTC One M8 5.0.1) it comes through fine. Because it works fine on some devices, I'm sure there's not a problem with my code, however I've posted a minimal test case below.

Can anyone can help me get my service reporting ids across all devices?

The A11y service

public class ViewIdLoggingAccessibilityService extends AccessibilityService {
  @Override
  public void onAccessibilityEvent(AccessibilityEvent event) {
      AccessibilityNodeInfo source = event.getSource();
      if (source == null) {
          Log.d("onAccessibilityEvent", "source was null for: " + event);
      } else {
          String viewIdResourceName = source.getViewIdResourceName();
          Log.d("onAccessibilityEvent", "viewid: " + viewIdResourceName);
      }
  }

  @Override
  public void onInterrupt() {
      Log.d("!# onInterrupt", "called");
  }
}

The AndroidManifest.xml

<manifest package="com.example.a11yservice"
          xmlns:android="http://schemas.android.com/apk/res/android"
    >

  <application
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme"
      >

    <service
        android:name=".ViewIdLoggingAccessibilityService"
        android:label="@string/view_id_logging_service_label"
        android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE"
        >
      <intent-filter>
        <action android:name="android.accessibilityservice.AccessibilityService" />
      </intent-filter>
      <meta-data
          android:name="android.accessibilityservice"
          android:resource="@xml/serviceconfig"
          />
    </service>

  </application>

</manifest>

serviceconfig.xml

<accessibility-service xmlns:android="http://schemas.android.com/apk/res/android"
    android:accessibilityEventTypes="typeViewClicked|typeViewFocused"
    android:accessibilityFeedbackType="feedbackGeneric"
    android:accessibilityFlags="flagReportViewIds"
    android:canRetrieveWindowContent="true"
    android:notificationTimeout="100" />

Answer 1

It's known issue and was posted to AOSP issue tracker some time ago. You can check status of issue here: " Accessibility Issue: flagReportViewIds has no effect on real devices in Android M ".

Unfortunately issue exists even on latest Android 7.0 but I found simple workaround. You can call refresh() method on AccessibilityNodeInfo object to refresh it and collect all missed data including id.

Something like that:

public void onAccessibilityEvent(AccessibilityEvent event) {
    AccessibilityNodeInfo ani = event.getSource();
    if (ani != null) {
        ani.refresh(); // to fix issue with viewIdResName = null on Android 6+
    }
}

Answer 2

I found that if the viewId isn't available, querying the focused element seems to work:

    AccessibilityNodeInfo source = findFocus(AccessibilityNodeInfo.FOCUS_INPUT);
    viewIdResourceName = source.getViewIdResourceName();

returns the correct view id