fix: KeyboardAvoidingView height when "Prefer Cross-Fade Transitions"…

… is enabled (facebook#34503)

Summary:
Fix `KeyboardAvoidingView`  height on iOS when "Prefer Cross-Fade Transitions" is enabled by adding an additional check to `_relativeKeyboardHeight` verifying if `prefersCrossFadeTransitions()` is true and `keyboardFrame.screenY` is `0` and treating this special case. The issue was caused  by the native RCTKeyboardObserver where the `endFrame` reported by `UIKeyboardWillChangeFrameNotification` returns `height = 0` when Prefer Cross-Fade Transitions" is enabled
and unfortunelly there isn't much we can do on the native side to fix it.

Closes facebook#31484
Closes facebook#29974

## Changelog

[iOS] [Fixed] - Fix KeyboardAvoidingView height when "Prefer Cross-Fade Transitions" is enabled

Pull Request resolved: facebook#34503

Test Plan:
**On iOS 14+**

1.  Access Settings > "General" > "Accessibility" > "Reduce Motion", enable "Reduce Motion" then enable "Prefer Cross-Fade Transitions".
2. Open the RNTester app and navigate to the KeyboardAvoidingView page
3. Focus and blur inputs and observe the keyboard behaving correctly

https://user-images.githubusercontent.com/11707729/186822671-801872be-7db1-4c5c-904b-1987441c1326.mov

Reviewed By: jacdebug

Differential Revision: D39055213

Pulled By: cipolleschi

fbshipit-source-id: fac17cbe02867e0fe522397f6cb59a8b51c1840f

Libraries/Components/Keyboard/KeyboardAvoidingView.js

@@ -23,6 +23,7 @@ import type {
   ViewLayoutEvent,
 } from '../View/ViewPropTypes';
 import type {KeyboardEvent, KeyboardMetrics} from './Keyboard';
+import AccessibilityInfo from '../AccessibilityInfo/AccessibilityInfo';
 
 type Props = $ReadOnly<{|
   ...ViewProps,
@@ -71,12 +72,24 @@ class KeyboardAvoidingView extends React.Component<Props, State> {
     this.viewRef = React.createRef();
   }
 
-  _relativeKeyboardHeight(keyboardFrame: KeyboardMetrics): number {
+  async _relativeKeyboardHeight(
+    keyboardFrame: KeyboardMetrics,
+  ): Promise<number> {
     const frame = this._frame;
     if (!frame || !keyboardFrame) {
       return 0;
     }
 
+    // On iOS when Prefer Cross-Fade Transitions is enabled, the keyboard position
+    // & height is reported differently (0 instead of Y position value matching height of frame)
+    if (
+      Platform.OS === 'ios' &&
+      keyboardFrame.screenY === 0 &&
+      (await AccessibilityInfo.prefersCrossFadeTransitions())
+    ) {
+      return 0;
+    }
+
     const keyboardY =
       keyboardFrame.screenY - (this.props.keyboardVerticalOffset ?? 0);
 
@@ -90,7 +103,7 @@ class KeyboardAvoidingView extends React.Component<Props, State> {
     this._updateBottomIfNecessary();
   };
 
-  _onLayout = (event: ViewLayoutEvent) => {
+  _onLayout = async (event: ViewLayoutEvent) => {
     const wasFrameNull = this._frame == null;
     this._frame = event.nativeEvent.layout;
     if (!this._initialFrameHeight) {
@@ -99,22 +112,22 @@ class KeyboardAvoidingView extends React.Component<Props, State> {
     }
 
     if (wasFrameNull) {
-      this._updateBottomIfNecessary();
+      await this._updateBottomIfNecessary();
     }
 
     if (this.props.onLayout) {
       this.props.onLayout(event);
     }
   };
 
-  _updateBottomIfNecessary = () => {
+  _updateBottomIfNecessary = async () => {
     if (this._keyboardEvent == null) {
       this.setState({bottom: 0});
       return;
     }
 
     const {duration, easing, endCoordinates} = this._keyboardEvent;
-    const height = this._relativeKeyboardHeight(endCoordinates);
+    const height = await this._relativeKeyboardHeight(endCoordinates);
 
     if (this.state.bottom === height) {
       return;