Allows RefreshControl to be mounted with refreshing = true

Summary:
RefreshControl did not start refreshing when refreshing was set to true initially. It also did not start refreshing on iOS when setting the prop from false to true without doing a pull to refresh gesture.

This was a pain in the ass to make work on iOS because UIRefreshControl seems super sensitive to when beginRefreshing can be called, for the initial render I need to call it in layoutSubviews. I also have to manually adjust the scrollview content offset when calling beginRefreshing. The code is a bit hacky but it was the only solution I found that was actually working.

Fixes #5716
Closes https://github.com/facebook/react-native/pull/5745

Reviewed By: svcscm

Differential Revision: D2910716

Pulled By: nicklockwood

fb-gh-sync-id: d60e73bcfe8d86bb01249ba5f17e6a23c5a5aff6

React/Views/RCTRefreshControl.m

@@ -11,18 +11,59 @@
 
 #import "RCTUtils.h"
 
-@implementation RCTRefreshControl
+@implementation RCTRefreshControl {
+  BOOL _initialRefreshingState;
+  BOOL _isInitialRender;
+}
 
 - (instancetype)init
 {
   if ((self = [super init])) {
     [self addTarget:self action:@selector(refreshControlValueChanged) forControlEvents:UIControlEventValueChanged];
+    _isInitialRender = true;
   }
   return self;
 }
 
 RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
+- (void)layoutSubviews
+{
+  [super layoutSubviews];
+  
+  // If the control is refreshing when mounted we need to call
+  // beginRefreshing in layoutSubview or it doesn't work.
+  if (_isInitialRender && _initialRefreshingState) {
+    [self beginRefreshing];
+  }
+  _isInitialRender = false;
+}
+
+- (void)beginRefreshing
+{
+  // When using begin refreshing we need to adjust the ScrollView content offset manually.
+  UIScrollView *scrollView = (UIScrollView *)self.superview;
+  CGPoint offset = {scrollView.contentOffset.x, scrollView.contentOffset.y - self.frame.size.height};
+  // Don't animate when the prop is set initialy.
+  if (_isInitialRender) {
+    // Must use `[scrollView setContentOffset:offset animated:NO]` instead of just setting
+    // `scrollview.contentOffset` or it doesn't work, don't ask me why!
+    [scrollView setContentOffset:offset animated:NO];
+    [super beginRefreshing];
+  } else {
+    // `beginRefreshing` must be called after the animation is done. This is why it is impossible
+    // to use `setContentOffset` with `animated:YES`.
+    [UIView animateWithDuration:0.25
+                          delay:0
+                        options:UIViewAnimationOptionBeginFromCurrentState
+                     animations:^(void) {
+                       [scrollView setContentOffset:offset];
+                     } completion:^(__unused BOOL finished) {
+                       [super beginRefreshing];
+                     }];
+  }
+}
+
 - (NSString *)title
 {
   return self.attributedTitle.string;
@@ -35,9 +76,15 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
 - (void)setRefreshing:(BOOL)refreshing
 {
-  if (super.refreshing != refreshing) {
+  if (self.refreshing != refreshing) {
     if (refreshing) {
-      [self beginRefreshing];
+      // If it is the initial render, beginRefreshing will get called
+      // in layoutSubviews.
+      if (_isInitialRender) {
+        _initialRefreshingState = refreshing;
+      } else {
+        [self beginRefreshing];
+      }
     } else {
       [self endRefreshing];
     }

ReactAndroid/src/main/java/com/facebook/react/views/swiperefresh/SwipeRefreshLayoutManager.java

@@ -71,8 +71,15 @@ public class SwipeRefreshLayoutManager extends ViewGroupManager<ReactSwipeRefres
   }
 
   @ReactProp(name = "refreshing")
-  public void setRefreshing(ReactSwipeRefreshLayout view, boolean refreshing) {
+  public void setRefreshing(final ReactSwipeRefreshLayout view, final boolean refreshing) {
-    view.setRefreshing(refreshing);
+    // Use `post` otherwise the control won't start refreshing if refreshing is true when
+    // the component gets mounted.
+    view.post(new Runnable() {
+      @Override
+      public void run() {
+        view.setRefreshing(refreshing);
+      }
+    });
   }
 
   @Override