Fix InputAccessoryView safe area when not attached to a TextInput (#21179)

Summary:
When using an InputAccessoryView attached to a TextInput the safe area insets are not applied properly. This uses different autolayout constraints that works in all cases I tested, roughly based on the technique used here https://github.com/stockx/SafeAreaInputAccessoryViewWrapperView/blob/master/SafeAreaInputAccessoryViewWrapperView/Classes/SafeAreaInputAccessoryViewWrapperView.swift#L38.
Pull Request resolved: https://github.com/facebook/react-native/pull/21179

Differential Revision: D9928503

Pulled By: hramos

fbshipit-source-id: b1b623334558093042fd94ac85e1b52dd16aa1a0

Libraries/Text/TextInput/RCTInputAccessoryView.m

@@ -42,7 +42,7 @@
 
 - (void)reactSetFrame:(CGRect)frame
 {
-  [_inputAccessoryView setFrame:frame];
+  [_inputAccessoryView reactSetFrame:frame];
 
   if (_shouldBecomeFirstResponder) {
     _shouldBecomeFirstResponder = NO;

Libraries/Text/TextInput/RCTInputAccessoryViewContent.m

@@ -12,6 +12,7 @@
 @implementation RCTInputAccessoryViewContent
 {
   UIView *_safeAreaContainer;
+  NSLayoutConstraint *_heightConstraint;
 }
 
 - (instancetype)init
@@ -19,31 +20,48 @@
   if (self = [super init]) {
     _safeAreaContainer = [UIView new];
     [self addSubview:_safeAreaContainer];
+
+    // Use autolayout to position the view properly and take into account
+    // safe area insets on iPhone X.
+    // TODO: Support rotation, anchor to left and right without breaking frame x coordinate (T27974328).
+    self.autoresizingMask = UIViewAutoresizingFlexibleHeight;
+    _safeAreaContainer.translatesAutoresizingMaskIntoConstraints = NO;
+
+    _heightConstraint = [_safeAreaContainer.heightAnchor constraintEqualToConstant:0];
+    _heightConstraint.active = YES;
+
+    if (@available(iOS 11.0, *)) {
+      [_safeAreaContainer.bottomAnchor constraintEqualToAnchor:self.safeAreaLayoutGuide.bottomAnchor].active = YES;
+      [_safeAreaContainer.topAnchor constraintEqualToAnchor:self.safeAreaLayoutGuide.topAnchor].active = YES;
+      [_safeAreaContainer.leadingAnchor constraintEqualToAnchor:self.safeAreaLayoutGuide.leadingAnchor].active = YES;
+      [_safeAreaContainer.trailingAnchor constraintEqualToAnchor:self.safeAreaLayoutGuide.trailingAnchor].active = YES;
+    } else {
+      [_safeAreaContainer.bottomAnchor constraintEqualToAnchor:self.bottomAnchor].active = YES;
+      [_safeAreaContainer.topAnchor constraintEqualToAnchor:self.topAnchor].active = YES;
+      [_safeAreaContainer.leadingAnchor constraintEqualToAnchor:self.leadingAnchor].active = YES;
+      [_safeAreaContainer.trailingAnchor constraintEqualToAnchor:self.trailingAnchor].active = YES;
+    }
   }
   return self;
 }
 
-- (void)didMoveToSuperview
+- (CGSize)intrinsicContentSize
 {
-
-#if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 110000 /* __IPHONE_11_0 */
-  // Avoid the home pill (in portrait mode)
-  // TODO: Support rotation, anchor to left and right without breaking frame x coordinate (T27974328).
-  if (@available(iOS 11.0, *)) {
-    if (self.window) {
-      [_safeAreaContainer.bottomAnchor
-       constraintLessThanOrEqualToSystemSpacingBelowAnchor:self.window.safeAreaLayoutGuide.bottomAnchor
-       multiplier:1.0f].active = YES;
-    }
-  }
-#endif
-
+  // This is needed so the view size is based on autolayout constraints.
+  return CGSizeZero;
 }
 
-- (void)setFrame:(CGRect)frame
+- (void)reactSetFrame:(CGRect)frame
 {
-  [super setFrame:frame];
+  // We still need to set the frame here, otherwise it won't be
+  // measured until moved to the window during the keyboard opening
+  // animation. If this happens, the height will be animated from 0 to
+  // its actual size and we don't want that.
+  [self setFrame:frame];
   [_safeAreaContainer setFrame:frame];
+
+  _heightConstraint.constant = frame.size.height;
+  [self layoutIfNeeded];
 }
 
 - (void)insertReactSubview:(UIView *)subview atIndex:(NSInteger)index

RNTester/js/InputAccessoryViewExample.js

@@ -58,6 +58,8 @@ class TextInputBar extends React.PureComponent<*, *> {
   }
 }
 
+const BAR_HEIGHT = 44;
+
 class InputAccessoryViewExample extends React.Component<*> {
   static title = '<InputAccessoryView>';
   static description =
@@ -65,8 +67,8 @@ class InputAccessoryViewExample extends React.Component<*> {
 
   render() {
     return (
-      <View>
-        <ScrollView keyboardDismissMode="interactive">
+      <>
+        <ScrollView style={styles.fill} keyboardDismissMode="interactive">
           {Array(15)
             .fill()
             .map((_, i) => <Message key={i} />)}
@@ -74,14 +76,21 @@ class InputAccessoryViewExample extends React.Component<*> {
         <InputAccessoryView backgroundColor="#fffffff7">
           <TextInputBar />
         </InputAccessoryView>
-      </View>
+      </>
     );
   }
 }
 
 const styles = StyleSheet.create({
+  fill: {
+    flex: 1,
+  },
   textInputContainer: {
     flexDirection: 'row',
+    alignItems: 'center',
+    borderTopWidth: 1,
+    borderTopColor: '#eee',
+    height: BAR_HEIGHT,
   },
   textInput: {
     flex: 1,