Add onSlidingComplete callbacks when sliders adjusted via a11y (#26600)

Summary:
When sliders are adjusted via accessibility, no onSlidingComplete callback is
generated. This causes problems for components which perform behavior in this
callback, and means that such components don't behave properly when adjusted via
accessibility. For example, if an app hosting a volume control slider only commits the volume change to the hardware on onSlidingComplete, it is impossible for a screen reader user to ever actually adjust the volume.

Ensure that sliders call the onSlidingComplete callback after adjusted via
accessibility.

## Changelog

[General] [Fix] - Add onSlidingComplete callbacks when sliders adjusted via a11y.

[CATEGORY] [TYPE] - Message
Pull Request resolved: #26600

Test Plan: Prior to this change, using the RNTester slider example with a screen reader, the onSlidingComplete callback tests never shows any callbacks when the slider is adjusted. With this change applied, the callback test will show a number of callbacks corresponding to the number of times the slider was adjusted via the screen reader.

Differential Revision: D17661157

Pulled By: cpojer

fbshipit-source-id: a6eedef099c6c1b571b290c329059ac9b69b53dd

Author: Marc Mulcahy

React/Views/RCTSlider.m

@@ -84,4 +84,24 @@ - (UIImage *)thumbImage
   return [self thumbImageForState:UIControlStateNormal];
 }
 
+- (void)accessibilityIncrement
+{
+  [super accessibilityIncrement];
+  if (_onSlidingComplete) {
+    _onSlidingComplete(@{
+        @"value": @(self.value),
+    });
+  }
+}
+
+- (void)accessibilityDecrement
+{
+  [super accessibilityDecrement];
+  if (_onSlidingComplete) {
+    _onSlidingComplete(@{
+        @"value": @(self.value),
+    });
+  }
+}
+
 @end

ReactAndroid/src/main/java/com/facebook/react/views/slider/ReactSliderManager.java

@@ -10,10 +10,14 @@
 import android.graphics.PorterDuff;
 import android.graphics.drawable.Drawable;
 import android.graphics.drawable.LayerDrawable;
+import android.os.Bundle;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.SeekBar;
 import androidx.annotation.Nullable;
+import androidx.core.view.AccessibilityDelegateCompat;
+import androidx.core.view.ViewCompat;
+import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.AccessibilityActionCompat;
 import com.facebook.react.bridge.ReactContext;
 import com.facebook.react.bridge.ReadableMap;
 import com.facebook.react.common.MapBuilder;
@@ -132,7 +136,9 @@ public Class getShadowNodeClass() {
 
   @Override
   protected ReactSlider createViewInstance(ThemedReactContext context) {
-    return new ReactSlider(context, null, STYLE);
+    final ReactSlider slider = new ReactSlider(context, null, STYLE);
+    ViewCompat.setAccessibilityDelegate(slider, sAccessibilityDelegate);
+    return slider;
   }
 
   @Override
@@ -256,4 +262,27 @@ public long measure(
   protected ViewManagerDelegate<ReactSlider> getDelegate() {
     return mDelegate;
   }
+
+  protected static class ReactSliderAccessibilityDelegate extends AccessibilityDelegateCompat {
+    private static boolean isSliderAction(int action) {
+      return (action == AccessibilityActionCompat.ACTION_SCROLL_FORWARD.getId())
+          || (action == AccessibilityActionCompat.ACTION_SCROLL_BACKWARD.getId())
+          || (action == AccessibilityActionCompat.ACTION_SET_PROGRESS.getId());
+    }
+
+    @Override
+    public boolean performAccessibilityAction(View host, int action, Bundle args) {
+      if (isSliderAction(action)) {
+        ON_CHANGE_LISTENER.onStartTrackingTouch((SeekBar) host);
+      }
+      final boolean rv = super.performAccessibilityAction(host, action, args);
+      if (isSliderAction(action)) {
+        ON_CHANGE_LISTENER.onStopTrackingTouch((SeekBar) host);
+      }
+      return rv;
+    }
+  };
+
+  protected static ReactSliderAccessibilityDelegate sAccessibilityDelegate =
+      new ReactSliderAccessibilityDelegate();
 }