Deconflict "bottom view" layout and keyboard animations.

SignalMessaging/ViewControllers/OWSViewController.m

@@ -23,6 +23,7 @@ UIInterfaceOrientationMask DefaultUIInterfaceOrientationMask(void)
 
 @property (nonatomic, weak) UIView *bottomLayoutView;
 @property (nonatomic) NSLayoutConstraint *bottomLayoutConstraint;
+@property (nonatomic) BOOL shouldAnimatedBottomLayout;
 
 @end
 
@@ -64,6 +65,22 @@ UIInterfaceOrientationMask DefaultUIInterfaceOrientationMask(void)
     return self;
 }
 
+#pragma mark - View Lifecycle
+
+- (void)viewDidAppear:(BOOL)animated
+{
+    [super viewDidAppear:animated];
+
+    self.shouldAnimatedBottomLayout = YES;
+}
+
+- (void)viewDidDisappear:(BOOL)animated
+{
+    [super viewDidDisappear:animated];
+
+    self.shouldAnimatedBottomLayout = NO;
+}
+
 - (void)viewDidLoad
 {
     [super viewDidLoad];
@@ -73,6 +90,8 @@ UIInterfaceOrientationMask DefaultUIInterfaceOrientationMask(void)
     }
 }
 
+#pragma mark -
+
 - (void)autoPinViewToBottomOfViewControllerOrKeyboard:(UIView *)view avoidNotch:(BOOL)avoidNotch
 {
     OWSAssertDebug(view);
@@ -185,11 +204,23 @@ UIInterfaceOrientationMask DefaultUIInterfaceOrientationMask(void)
     // bar.
     CGFloat offset = -MAX(0, (self.view.height - self.bottomLayoutGuide.length - keyboardEndFrameConverted.origin.y));
 
-    // There's no need to use: [UIView animateWithDuration:...].
+    // UIKit by default animates all changes in response to keyboard events.
-    // Any layout changes made during these notifications are
+    // We want to suppress those animations if the view isn't visible,
-    // automatically animated.
+    // otherwise presentation animations don't work properly.
-    self.bottomLayoutConstraint.constant = offset;
+    dispatch_block_t updateLayout = ^{
-    [self.bottomLayoutView.superview layoutIfNeeded];
+        // There's no need to use: [UIView animateWithDuration:...].
+        // Any layout changes made during these notifications are
+        // automatically animated.
+        self.bottomLayoutConstraint.constant = offset;
+        [self.bottomLayoutView.superview layoutIfNeeded];
+    };
+
+
+    if (self.shouldAnimatedBottomLayout) {
+        updateLayout();
+    } else {
+        [UIView performWithoutAnimation:updateLayout];
+    }
 }
 
 #pragma mark - Orientation