Fix modal and alert dismissal bugs on iOS [v2] (facebook#22237)

Author: sryze

React/Modules/RCTAlertManager.m

@@ -30,6 +30,7 @@ @interface RCTAlertManager()
 @implementation RCTAlertManager
 {
   NSHashTable *_alertControllers;
+  UIWindow *_window;
 }
 
 RCT_EXPORT_MODULE()
@@ -90,11 +91,16 @@ - (void)invalidate
     }
   }
 
-  UIViewController *presentingController = RCTPresentedViewController();
-  if (presentingController == nil) {
-    RCTLogError(@"Tried to display alert view but there is no application window. args: %@", args);
-    return;
-  }
+  CGSize screenSize = [UIScreen mainScreen].bounds.size;
+  self->_window = [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, screenSize.width, screenSize.height)];
+#if TARGET_OS_TV
+  self->_window.windowLevel = UIWindowLevelNormal + 1;
+#else
+  self->_window.windowLevel = UIWindowLevelStatusBar + 1;
+#endif
+  UIViewController *presentingController = [UIViewController new];
+  self->_window.rootViewController = presentingController;
+  self->_window.hidden = NO;
 
   UIAlertController *alertController = [UIAlertController
                                         alertControllerWithTitle:title
@@ -152,6 +158,7 @@ - (void)invalidate
     [alertController addAction:[UIAlertAction actionWithTitle:buttonTitle
                                                         style:buttonStyle
                                                       handler:^(__unused UIAlertAction *action) {
+      self->_window = nil;
       switch (type) {
         case RCTAlertViewStylePlainTextInput:
         case RCTAlertViewStyleSecureTextInput:

React/Views/RCTModalHostView.m

@@ -159,7 +159,9 @@ - (void)didUpdateReactSubviews
 - (void)dismissModalViewController
 {
   if (_isPresented) {
-    [_delegate dismissModalHostView:self withViewController:_modalViewController animated:[self hasAnimationType]];
+    [_delegate dismissModalHostView:self
+                 withViewController:_modalViewController
+                           animated:[self hasAnimationType]];
     _isPresented = NO;
   }
 }
@@ -173,7 +175,7 @@ - (void)didMoveToWindow
   if (!self.userInteractionEnabled && ![self.superview.reactSubviews containsObject:self]) {
     return;
   }
-
+  
   if (!_isPresented && self.window) {
     RCTAssert(self.reactViewController, @"Can't present modal view controller without a presenting view controller");
 

React/Views/RCTModalHostViewManager.m

@@ -75,7 +75,19 @@ - (void)presentModalHostView:(RCTModalHostView *)modalHostView withViewControlle
   if (_presentationBlock) {
     _presentationBlock([modalHostView reactViewController], viewController, animated, completionBlock);
   } else {
-    [[modalHostView reactViewController] presentViewController:viewController animated:animated completion:completionBlock];
+    UIViewController *topViewController = [modalHostView reactViewController];
+    while (topViewController.presentedViewController != nil) {
+      if ([topViewController.presentedViewController isKindOfClass:UIAlertController.class]) {
+        // Don't present on top of UIAlertController, this will mess it up:
+        // https://stackoverflow.com/questions/27028983/uialertcontroller-is-moved-to-buggy-position-at-top-of-screen-when-it-calls-pre
+        [topViewController dismissViewControllerAnimated:animated completion:^{
+          [topViewController presentViewController:viewController animated:animated completion:completionBlock];
+        }];
+        return;
+      }
+      topViewController = topViewController.presentedViewController;
+    }
+    [topViewController presentViewController:viewController animated:animated completion:completionBlock];
   }
 }
 
@@ -89,7 +101,13 @@ - (void)dismissModalHostView:(RCTModalHostView *)modalHostView withViewControlle
   if (_dismissalBlock) {
     _dismissalBlock([modalHostView reactViewController], viewController, animated, completionBlock);
   } else {
-    [viewController.presentingViewController dismissViewControllerAnimated:animated completion:completionBlock];
+    if (viewController.presentedViewController && viewController.presentingViewController) {
+      // Ask the presenting view controller to dismiss any view controllers presented on top of the modal host
+      // together with the host itself.
+      [viewController.presentingViewController dismissViewControllerAnimated:animated completion:completionBlock];
+    } else {
+      [viewController dismissViewControllerAnimated:animated completion:completionBlock];
+    }
   }
 }